What is colorectal cancer?

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What is colorectal cancer?






Colorectal cancer, or cancer of the large intestine, is the third most common form of cancer in the United States and the third most common cause of death due to cancer. In 1994 alone, there were 150,000 new cases of colon cancer diagnosed and 56,000 deaths due to colon cancer in the US. Because colorectal cancer may go undiagnosed for a while and may spread rapidly, only 60% of people diagnosed with colon cancer survive for five years past the time of diagnosis. In general, this form of cancer affects more men than women over the age of 50 years.


Colorectal cancer refers to cancers that occur in the large intestines. Food enters the large intestine and travels through the ascending colon, the transverse colon, the descending colon, the sigmoid colon, the rectum, and then out of the body. Colorectal cancer can occur anywhere in the colon or in the rectum. In general, the risk factors for colon cancer and rectal cancer are the same.


Worldwide, there are very great differences in the incidence of colon cancer. Some countries may have 10-20 times the rate of other countries. Unfortunately, when people from an area with a very low rate emigrate to an area with a higher rate, their incidence increases to match the new area within one or two generations.


Although genetics may play a role in the disease, many researchers believe that as much as 90% of the differences in rates between areas can be explained by dietary factors alone. Fortunately, diet is something that can be changed.


Symptoms


Symptoms of colorectal cancer include lower abdominal pain that is constant or gets increasingly worse, changes in bowel habits, such as a change to recurrent diarrhea or constipation, blood in the stools, vomiting, anemia, or weight loss that occurs without a change in eating habits. Any of these symptoms should prompt someone to seek a more thorough medical examination.


Unfortunately, however, many people with colon cancer don't have any of these symptoms until very late in the disease. For this reason, people are urged to see their doctors every year. Doctors can perform a very sensitive test for blood in the stools, which is often the first sign of colon cancer. Doctors can also perform tests called a colonoscopy or a sigmoidoscopy, which basically examine the inside of the rectum and colon, looking for actual colon cancer lesions or tumors.


Regular doctor visits are the key to early detection and treatment of colon cancer. If the disease is caught early, it will be much easier to treat successfully than if it is caught after it has spread to other locations.


The Process


Normally, the cell's DNA organizes the activities of that cell. It's the blueprint for everything the cell produces and does. Every cell in the body, with few exceptions, has the same exact DNA as every other cell in the body. The main difference between types of cells is which portions of their DNA are currently being used to control the cell's activities.


When cells divide, the cells around them tell them what kind of cell they are going to be, all based on which parts of their DNA are active. For example, cells of the colon have different functions than cells of the liver or kidney. These differences are based on which parts of their DNA are to be working at the time. This process is called differentiation and it is very closely and carefully maintained in order for the body to function properly as a whole.


Damage to the DNA of cells happens constantly throughout the day. What usually occurs is that the damage is either repaired by mechanisms inside the cell, or the damage weakens the cell, causing it to die through a process called apoptosis. Cells may also become dysfunctional and start to produce substances that they wouldn't normally produce. In these cases, the cells of the immune system detect the fact that this cell is now different and destroy it before it does any damage.


In some cases, however, these protective mechanisms fail and a cell with damage to its DNA is able to survive and divide. Most times, this doesn't really amount to anything. Eventually the cells die, or the damage is so slight that the cells can still function properly.


If the cell is still being exposed to large amounts of free radicals or carcinogens, the DNA can become damaged even further. When this occurs, the cells may start to lose their normal function and start to divide rapidly. If they are not detected and destroyed by the immune system, they can continue to divide, producing the beginnings of a tumor.


Over time, the cells can continue to accumulate DNA damage and divide rapidly, leading to a mass in the colon or rectum. The mass may grow large enough to produce a blockage in the intestines, which can be life-threatening in and of itself. Or the mass may start to grow outwards into the area, causing damage to local nerves or blood vessels and putting pressure on other organs. Or the tumor cells may mutate until they develop the ability to metastasize (that is, spread to other areas), such as the liver or bone.


Once the cells spread to other areas, they may continue to divide and grow into masses that are large enough to cause damage and interrupt the function of these other organs. Death from colon cancer and cancer in general is typically the result of organ damage caused by masses of cancer cells that have grown so large that they interfere with normal organ function.


The good news is that this is typically a slow process that takes several years to develop. Although cancer may appear to progress very rapidly once it is diagnosed, there are many steps between the initial DNA damage and the mutations that must occur for a tumor or metastatic cancer to develop to the point of being detectable.


Causes


The cells of the colon and rectum are constantly exposed to chemicals that irritate them and that are considered carcinogenic, or cancer-causing. Some of the main carcinogens are the bile salts produced by the liver. These substances are secreted into the intestines to help with digestion of fats in the diet.


Unfortunately, certain kinds of bacteria that live in the intestines can convert these bile salts into carcinogenic substances. These carcinogens can enter the cells themselves and damage the DNA, or they may increase the amounts of pro-inflammatory chemicals, called prostaglandins, in the area, which then leads to increased levels of free radicals. These free radicals can then enter the cells and cause DNA damage.


In addition, certain substances found in food itself can be carcinogenic. Some of the main types of carcinogens in the American diet are called heterocyclic amines. These are formed in meats, including red meat, chicken, and fish, when they are heated at very high temperatures, such as during grilling, barbequing, broiling, or frying. Other types of carcinogens, known as polycyclic aromatic hydrocarbons, can be formed in foods when they are cooked over an open flame or smoked. These carcinogens are dangerous to the cells of the colon and rectum and produce the DNA damage that can lead to cancer.


Reducing one's risk of developing colon cancer involves avoiding or minimizing exposure to those things that can increase risk.


One protective action you can take when eating grilled meat is to be sure to enjoy it with a serving of healthy steamed red cabbage or Brussels sprouts, an especially delicious addition to your meal when tossed with virgin olive oil, balsamic vinegar and lightly roasted walnuts. These cruciferous vegetables greatly increase our body's ability to detoxify heterocyclic amines, the carcinogenic compounds produced when meat is grilled or otherwise charbroiled.
In a study published in Carcinogenesis (Kassie F, Uhl M, et al., February 2003), researchers looked at the effects of drinking water supplemented with Brussels sprouts or red cabbage juices on the liver and colon of animals that were also given a heterocyclic amine carcinogen.


Brussels sprouts reduced the development of pre-cancerous cells 41-52% in the colon and 27-67% in the liver, and drastically diminished the size (85-91%) of pre-cancerous lesions in the liver.


Red cabbage moderately decreased (19-50%) the number of pre-cancerous lesions that developed in the liver and markedly reduced (41-83%) the size of those that did occur.


These highly protective effects are due to crucifers' ability to significantly increase the activity of enzymes involved in both Phase I (CYP4501A2) and Phase II (glucuronidation via UDPGT-2) detoxification. Brussels sprouts' stronger protective effects are thought to be due to the fact that this cruciferous vegetable contains 2-3 times the amount of phytonutrients called glucosinolates than are found in red cabbage. Glucosinolates increase Phase II glucuronidation activity, one of the primary pathways through which toxins that are made even more dangerous by Phase I, are rendered water-soluble and ready for elimination from the body.


One risk that cannot be changed is genetic susceptibility. Colon cancer tends to run in families and some people carry genes that put them at a much higher risk for colon cancer than others. Fortunately, though, genetic risk does not guarantee that one will wind up with colorectal cancer. Many other risk factors can be modified to reduce the possibility of developing this disease.


For example, obesity and a lack of physical activity are both associated with an increased risk for colon cancer. Studies have shown that people who are obese have an increased incidence of colon cancer. It's unknown whether this is due to lack of physical activity or certain dietary habits that are associated with obesity and are also risk factors, or whether it is something to do with the obesity itself.


Also, even moderate physical activity and exercise can greatly reduce one's risk for developing colon cancer, by as much as 50% according to some studies. In addition to other benefits, such as increased circulation and improved immune function, moderate physical activity can improve the movement of food through the colon, thereby reducing the amount of time that the colon cells spend in contact with carcinogenic chemicals and bile salts. Another important risk factor for colon cancer development is cigarette smoking. By far the most important factor in reducing colorectal cancer risk is diet.


Dietary Causes


Diet is considered the most important factor in the development of colorectal cancer. Some researchers report that differences in dietary habits account for up to 90% of the differences in incidence rates seen between different areas of the world.


Other researchers propose that dietary factors may explain up to 90% of all cases of colon cancer. The main dietary factors that contribute to an increased risk of colon cancer include total fat intake, saturated or animal fat intake, consumption of red meat, processed meats and meat cooked at very high temperatures, sugar consumption, alcohol use, especially commercial beer, and overeating.


In contrast, diets high in vegetables, total fiber, fruits, fish, whole grains, and fermented dairy products such as yogurt, have all been shown to significantly reduce one's risk of developing colon cancer.


Data compiled in The European Prospective Investigation into Cancer and Nutrition indicates that risk of colorectal cancer increases with increased consumption of red or processed meats, but decreases with increasing intake of fish. One of the largest nutrition trials carried out to date, this study, published June 2005, followed 478,040 men and women aged 35 to 70 from 10 European countries.


People eating more than 160 grams of red or processed meat daily were 35% more likely to develop bowel cancer than those eating less than 20 grams a day.


Those eating more than 80 grams of fish daily were found to have a 31% reduction in their risk of colorectal cancer.


Eating chicken appeared to have no effect on bowel cancer risk, but a low fiber diet, obesity and lack of physical activity also increased risk of the disease.


The study's most important take home message: more than two-thirds of colorectal cancer cancer cases could be avoided by changes in lifestyle.




Nutrient Needs


Nutrients That May Reduce Risk of Colorectal Cancer


Fiber


It's estimated that colon cancer risk in the United States could be reduced by 31% with even a moderate increase in daily fiber intake. Other studies show up to a 50% decrease in risk with increased consumption of fiber-rich foods.
A study published in the November 2003 issue of JAMA confirms the association between higher consumption of cereal fiber and a lower risk of colon cancer. The study, a 35-month prospective trial involving 3,121 patients aged 50 to 75 years found an inverse association between consumption of cereal fiber (fiber intake more than 4.2 grams per day), vitamin D (intake greater than 645 IU per day), and the daily use of non-steroidal anti-inflammatory drugs (NSAIDS such as aspirin) and colon cancer. High intake of fiber reduced colon cancer risk by 5%, of vitamin D by 6%, and NSAIDS by 34%. Smoking was associated with an 85% increased risk of colon cancer and current moderate to heavy alcohol use with a 2% increase in risk. A diet rich in fiber and vitamin D would provide an 11% reduction in colon cancer risk. (December 30, 2003)
Researchers in the Department of Nutritional Sciences at Pennsylvania State University found improved insulin regulation and better inflammatory status if men who were at risk of colorectal cancer consumed about 20-40 grams of fiber per day, including fiber from vegetables, fruits, and legumes. These fiber levels were at least twice as high as study participants had been consuming prior to their participation in the study.


Unfortunately, most people in the United States do not get nearly as much fiber in their diets as they should be getting. Fiber decreases colon cancer risk by several different mechanisms. One way is by binding to bile salts.


As mentioned above, bile salts can be converted by certain intestinal bacteria into carcinogens. By binding to the bile salts, fiber helps to reduce this possibility. Fiber also helps to add bulk to the stool, which results in a dilution of the concentration of bile in the colon, further decreasing exposure.


By adding bulk to the stool, fiber also increases the rate at which stool is eliminated from the body, reducing the amount of time that the colon cells spend in contact with the bile salts.


Fiber also encourages the growth of beneficial bacteria in the large intestine. These bacteria have been shown to bind to certain carcinogens and also to prevent the activation of other carcinogens that may occur in the colon.


Fiber in the intestines can be fermented by normal flora to substances called short chain fatty acids or volatile fatty acids. These substances have been shown to have very beneficial effects on colon cells. One of these chemicals, known as butyrate, is produced from a variety of healthy foods, including root vegetables like chicory and burdock root, onions and chives, asparagus, and whole grains like rye, wheat, and oats.


Butyrate has been demonstrated to decrease the proliferation and increase the apoptosis of mutated cells, while at the same time helping to protect healthy cells from damage due to free radicals. It also acts as a fuel source for colon cells, thereby supporting their healthy function. Wheat bran itself has been shown in a number of studies to be very good for the prevention of colon cancer.


Some excellent food sources of fiber include raspberries, mustard greens, turnip greens, collard greens, broccoli, cauliflower, and Swiss chard.


Calcium and Vitamin D


Higher intakes of calcium and vitamin D are associated with a significant decrease in risk of both colon and rectal cancer. People with low intake of these two nutrients have been shown to have twice the risk of developing colorectal cancer as people with higher intakes. Studies have shown that people with higher blood levels of vitamin D had a 70% reduction in risk.


These nutrients reduce colon cancer risk by several mechanisms. Calcium has the ability to bind to bile salt, thus reducing their exposure to colon cells. Both calcium and vitamin D have been shown to reduce excessive proliferation of colon and rectal cells, increase the normal process of apoptosis, and improve the necessary differentiation of these cells. These effects have been demonstrated even in those who continue to consume a high-fat diet, which has been identified as another risk factor for colorectal cancer.


Diets high in calcium or in oxidation-resistant fats such as olive oil, may prevent the possible cancer-promoting effect of red meat, suggests a study published in the August 2003 issue of Carcinogenesis. It's generally accepted that a high intake of red meat, but not of white meat, is associated with an increased risk of colon cancer. Researchers believe this is due to the fact that red, but not white meat contains haemin, a form of iron (specifically, a chloride of heme in which He2+ has become He3+). It is thought that haemin, by promoting free radical formation and activity, increases the cellular damage that ultimately results in colon cancer. In this study, rats that already had abnormal colonic cell growths (called aberrant crypt foci) were injected with a carcinogenic chemical (azoxymethane) and then fed a variety of experimental high haemin-containing diets. While in rats given only a high haemin diet, free radical production and abnormal colonic cell growth escalated, in those who were also supplemented with calcium or with olive oil and antioxidants, free radical production remained normal and so did colon cells.
Mustard greens, turnip greens, spinach and collard greens are some excellent food sources of calcium. Shrimp and fortified milk are two very good sources of vitamin D.


Folate


A high intake of folate, or folic acid, has been shown in several studies to decrease the risk of colon cancer. One study showed the risk of colon cancer in certain high-risk patients was reduced by 62% with a high intake of folate. In addition, several studies have shown that those who have a low intake of dietary folate are at a greatly increased risk of developing colon cancer.


Folate is needed for the proper production of DNA in replicating cells. Low folate has been shown to cause breakages of DNA, which can lead to an increased rate of mutations, eventually contributing to the development of cancer. The combination of a low folate diet and regular alcohol use has been shown to especially increase the risk of colon cancer. Getting enough folate in the diet is important for protecting against these DNA mutations.


Excellent sources of folate include: spinach, parsley, broccoli, beets,turnip greens, asparagus, romaine lettuce, lentils, and calf's liver.


Vitamin B6


A diet high in foods rich in vitamin B6 may reduce risk of colorectal cancer, particularly in persons who consume moderate to large amounts of alcohol, suggests a study published in the June 2005 issue of Gastroenterology.


Swedish scientists at the Karolinska Institute in Stockholm, Sweden, analyzed data collected from 61,433 women aged 40-75 years, who were followed for approximately 15 years.


Participants receiving the most vitamin B6 from their food had a 34% lower risk of colorerctal cancer compared to women with the lowest intakes of this B vitamin. When a sub-group of the women who were moderate to high alcohol consumers was evaluated, those who consumed the most foods rich in vitamin B6 had a more than 70% reduction in risk of colorectal cancer compared to women with the lowest intakes. Why are foods rich in vitamin B6—such as fish (tuna, salmon, cod, snapper, halibut), bananas, avocado, chicken and turkey breast—so protective? Most likely because Vitamin B6 is involved in almost 100 enzymatic reactions including DNA synthesis, repair and methylation, and lack of adequate supplies of the vitamin results in disruption of such functions, enhancing risk of carcinogenesis.


Vitamin B12


Vitamin B12 is similar to folate in that it is also needed for the proper production of DNA. Although there are few studies linking vitamin B12 to colon cancer risk specifically, low levels of vitamin B12 have been shown to lead to increased DNA breakage and mutations. People increasing their folate intakes should make sure they are getting enough vitamin B12 in their diets as well.
Excellent food sources of vitamin B12 include calf liver and snapper.


Selenium


Selenium is a mineral needed for the proper function of the antioxidant system of the body. Several studies have shown that adequate amounts of selenium in the diet can protect against many different types of cancer, including colon cancer. A low selenium intake can lead to excessive amounts of free radicals and damage to DNA.
In one study, patients who were given selenium-rich foods had a 58% decreased risk for developing colon cancer. In order to gain the maximum benefit from selenium, researchers recommend also following a low-fat diet. Selenium is able to work best when there is an adequate intake of vitamin E.


Some excellent sources of selenium include crimini mushrooms, cod, shrimp, salmon, snapper, yellowfin tuna, and calf liver.


Vitamin E


Vitamin E is the main fat-soluble antioxidant in the body. It's needed to decrease the levels of free radicals and prevent the damage they may cause. It has also been shown to improve the function of the immune system in the colon, allowing the body to combat cancer cells.
Studies have shown that those with the greatest intake of vitamin E have approximately 1/3 the risk of developing colon cancer when compared to those with the lowest intake. It's important that people increase their intake of natural forms of vitamin E, not the synthetic forms found in some supplements. Mustard greens, chard, turnip greens, and sunflower seeds are a few excellent sources of vitamin E.


Vitamin C


Vitamin C is one of the main water-soluble antioxidants in the body. It's also needed to decrease levels of free radicals that can cause damage to cells. Also like vitamin E, vitamin C is needed for the proper function of the immune system. Some studies have shown that vitamin C intake can help to decrease the incidence of colon tumors. Other studies have shown a link between increased vitamin C intake and a decreased risk for colon cancer, possibly by as much as 40%.
Excellent food sources of vitamin C include broccoli, parsley, bell peppers, strawberries, cauliflower, lemons, mustard greens, Brussels sprouts, papaya, kale, cabbage, spinach, kiwifruit, cantaloupe, oranges, grapefruit, tomatoes, chard, collard greens, raspberries, peppermint leaves, asparagus, celery, fennel bulb, pineapple, and watermelon.


Limonoids


In animal studies and laboratory tests with human cells, compounds in citrus fruits called limonoids have been shown to help fight cancers of the mouth, skin, lung, breast, stomach and colon. Now, scientists from the US Agricultural Research Service have shown that our bodies can readily absorb and utilize a very long-acting limonoid called limonin that is present is citrus fruits in about the same amount as vitamin C.


In citrus fruits, limonin is present in the form of limonin glucoside, in which limonin is attached to a sugar (glucose) molecule. Our bodies easily digest this compound, cleaving off the sugar and releasing limonin.


In the ARS study, 16 volunteers were given a dose of limonin glucoside in amounts ranging from those that would be found in from 1 to 7 glasses of orange juice. Blood tests showed that limonin was present in the plasma of all except one of the subjects, with concentrations highest within 6 hours after consumption. Traces of limonin were still present in 5 of the volunteers 24 hours after consumption!


Limonin's bioavailability and persistence may help explain why citrus limonoids are potent anti-carcinogens that can continuously prevent cancerous cells from proliferating. Other natural anti-carcinogens are available for much less time; for example, the phenols in green tea and chocolate remain active in the body for just 4 to 6 hours. Food sources of limonoids include oranges, grapefruit, lemons and limes.


Grapefruit


Grapefruit are particularly recommended. Not only are grapefruit rich in vitamin C, but new research presented August 2004 at the 228th National Meeting of the American Chemical Society provides evidence that grapefruit helps protect against lung and colon cancer.


In humans, drinking three 6-ounce glasses of grapefruit juice a day was shown to reduce the activity of an enzyme that activates cancer-causing chemicals found in tobacco smoke. In rats whose colons were injected with carcinogens, grapefruit and its isolated active compounds (apigenin, hesperidin, limonin, naringin, naringenin, nobiletin) not only increased the suicide (apoptosis) of cancer cells, but also the production of normal colon cells. Researchers also confirmed that grapefruit may help prevent weight gain by lowering insulin levels, and high insulin levels have also been linked to an increased risk for colon and other cancers.


New insight into how grapefruit protects against cancer


Grapefruit juice significantly increases the production and activity of liver detoxification enzymes responsible for preparing toxic compounds for elimination from the body.


The liver clears out toxins, including carcinogens, using a two step process called Phase I and Phase II detoxification. In the first part of this process, Phase I, enzymes belonging to the cytochrome P450 family, work on the toxin to make it more attractive to enzymes involved in the second part of the process, Phase II. Unfortunately, the action of Phase I enzymes often renders the toxin not only more attractive to Phase II enzymes, but even more dangerous, and some foods contain compounds that only increase the activity of Phase I without also turning up Phase II.


Grapefruit increases the activity not only of the Phase I enzyme CYP1A1, but also that of NAD(P)H:quinone reductase 1, a Phase II detoxification enzyme that protects cells against oxidative stress and toxic quinones. The end result: grapefruit works in both Phase I and Phase II to enhance the liver's ability to remove cancer-causing toxins.


Beta-carotene


Beta-carotene and other carotenoids have been shown in some studies to decrease the risks of developing both colon cancer and rectal cancer. They work similarly to other antioxidants in decreasing the amount of free radicals in the body. Carotenoids have also been shown to increase cell differentiation and protect cells against carcinogenic chemicals that could damage DNA. Vitamin A, which is structurally similar to beta-carotene, may help to decrease risk by preventing excessive colon cell proliferation and tumor formation.


Excellent food sources of vitamin A/beta-carotene include sweet potatoes, carrots, calf liver, kale, winter squash, collard greens, chard, cantaloupe, mustard greens, romaine lettuce, spinach, parsley, cayenne pepper, peppermint leaves, Brussels sprouts, tomatoes, broccoli, asparagus, and apricots.


Lycopene


A carotenoid nutrient found in tomatoes (and everything made from them), lycopene has been extensively studied for its antioxidant and cancer-preventing properties. In contrast to many other food phytonutrients, whose effects have only been studied in animals, lycopene from tomatoes has been repeatedly studied in humans and found to be protective against a growing list of cancers including colorectal cancer. A study published in the November 2003 issue of the American Journal of Clinical Nutrition found that in patients with colorectal adenomas, a type of polyp that is the precursor for most colorectal cancers, blood levels of lycopene were 35% lower compared to study subjects with no polyps. Blood levels of beta-carotene also tended to be 25.5% lower, although according to researchers, this difference was not significant. In their final (multiple logistic regression) analysis, only low levels of plasma lycopene (less than 70 microgram per liter) and smoking increased the likelihood of colorectal adenomas, but the increase in risk was quite substantial: low levels of lycopene increased risk by 230% and smoking by 302%. Well known for being abundant in tomatoes and particularly well absorbed from cooked tomato products containing a little fat such as olive oil, lycopene is also present in high amounts in watermelon and mangoes.
Omega-3 fatty acids


Omega-3 fatty acids are types of fats needed by our cells for proper functioning. They're the main types of fats found in fish oils. Numerous studies have shown a link between the intake of omega-3 fats, fish oils, or fish in general and a decreased risk for colon cancer. EPA, a type of omega-3 fatty acid found in fish oil, has been shown to decrease the formation of tumors in the colon.
A study published in Free Radical Biology (Bancroft LK, Lupton JR) may help explain why. Omega-3 fats are believed to reduce colon cancer risk by decreasing the production of the pro-inflammatory prostaglandins in the intestines. Since inflammation produces free radicals and DNA damage, decreasing the production of prostaglandins can prevent this from occurring. In this study, when mice were given either fish oil or corn oil (which is high in potentially inflammatory omega 6 fatty acids) and then dosed with dextran sodium sulfate, a chemical known to provoke an inflammatory response that can lead to DNA damage, not only did the fish oil lessen the inflammatory response, but it also caused an increase in the apoptosis of those cells that were damaged. (Apoptosis is the self-destruct sequence the body uses to eliminate cancerous cells).
A review of 91 studies on the relationship between diet and cancer published in the International Journal of Cancer(Reddy B.) provides substantial evidence that diets rich in the omega-3 fats found in cold water fish help prevent colon cancer. The review includes studies conducted in the U.S., Canada, and 22 European countries which show that the tumor-promoting effect seen with dietary fat depends on which type of fat it is, and that colon cancer risk is related more to what type, rather than how much fat is eaten. Although the ways in which omega-3 fats exert their protective effects is not yet fully understood, it appears that the fats a person eats affect the amount of bile acids he or she excretes. People eating a typical Western diet, which is high in saturated and omega-6 fats, who are at higher risk of colon cancer, also excrete high levels of bile acids. Excess bile acids have been shown to stimulate an inflammatory chemical called protein kinase C, to induce cell proliferation, and act as promoters in colon carcinogenesis. Omega-3 fats are thought to prevent carcinogen activation by decreasing DNA-damage, enhancing DNA repair, and enhancing apoptosis (cell suicide) in carcinogenic colonic cells.


Omega-3-Rich Fish Protective against Colorectal Cancer


A diet rich in the omega-3 fats found in cold water fish greatly reduces risk of colorectal cancer, indicates a study comparing 1,455 subjects with colorectal cancer to 1,455 matched healthy controls. Those whose diets provided the most omega-3s had a 37% reduction in colorectal cancer risk, compared to those whose diets provided the least. Colorectal cancer risk was 41% lower in those with the highest average intake of EPA, and 37% lower in those whose diets supplied the most DHA. Am J Epidemiol. 2007 Jul 15;166(2):181-95


Practical Tip: Each of the World's Healthiest Foods' fish is a good to excellent source of omega-3s. Let our Recipe Assistant provide you with delicious, quick ways to add more omega-3s to your healthy way of eating.


Omega-3s Slash Men's Risk of Colorectal Cancer by Reducing Inflammation Naturally


Colorectal cancer accounts for 9% of new cancer cases worldwide, and risk for this cancer is highest is in the U.S. and Europe. A healthy way of eating that features foods rich in omega-3 fats— cold water-fish and flaxseed—may decrease men's risk for this cancer by as much as 66%, suggests a study in Cancer Epidemiology Biomarkers & Prevention (Hall MN, Campos H, et al.)


Omega-3 fatty acids lower colorectal cancer risk because their consumption naturally results in increased production of anti-inflammatory prostaglandins and decreased production of pro-inflammatory prostaglandins. This happy combination occurs because both omega-3 fatty acids and omega-6 fatty acids (which are concentrated in meats and some vegetable oils, such as corn oil), compete for the same cyclooxygenase enzymes for their conversion into prostaglandins. The presence of more omega-3s thus translates not only into the production of more anti-inflammatory prostaglandins, but fewer pro-inflammatory prostaglandins.


Omega-3s reduce inflammation and, by doing so, reduce risk of colon cancer, because inflammation has been linked to cancer cell formation and proliferation.


The research on omega-3s' protective effects against colorectal cancer, led by Megan Hall with a team from Harvard Medical School and Brigham and Women's Hospital, looked to see if there were a link between concentrations of omega-3 and omega-6 fatty acids in the blood of 178 men with colorectal cancer and 282 cancer-free controls, who were matched by age and smoking habits.


After adjusting the results potential confounding factors, the researchers found that men with the highest blood levels of omega-3 fatty acids had a 40% reduced risk of colorectal cancer compared to those with the lowest blood levels.


When they looked only at the subset of men who were not taking aspirin, men with the highest blood levels of omega-3 fatty acids were found to have a 66% reduced risk of colorectal cancer compared to those with the lowest blood levels.


For men taking aspirin, no additional benefit was seen for increasing blood levels of omega-3 fatty acids, most likely because aspirin also lessens inflammation. However, aspirin does so by blocking the activity of the cyclooxygenase enzyme, which results not only in preventing formation of pro- but also anti-inflammatory prostaglandins.


Possibly because it blocks formation of both types of prostaglandins, aspirin is less effective in reducing colon cancer risk than the omega-3 fatty acids. According to the results of a Cochrane Systematic Review in the Annals of Internal Medicine, in cohort studies, regular use of aspirin was associated with a 22% reduced risk of colorectal cancer, while two randomized controlled trials of low-dose aspirin failed to show any protective effect. (Dube C, Rostom A, et al.)


When used at a high does for periods longer than 10 years, aspirin's benefits were more evident, but so were its dangerous side-effects: the higher the dose of aspirin and the longer its use, the higher the risk of gastrointestinal bleeding and ulcers.


Practical Tip: Lower your risk of colorectal cancer significantly—and safely—by enjoying a healthy way of eating that features omega-3-rich flaxseeds, walnuts, and fish, such as wild Alaskan salmon, Pacific "troll caught" tuna, sardines, cod, and halibut.


Want to learn more about these colon cancer-preventive essential fats? Click omega-3 fats. For suggestions as to how to enjoy more omega-3-rich foods as part of your healthy way of eating, click on the Recipe Assistant, select the fish, nut or seed desired from the healthy foods list, and click on the Submit button. A list containing links to all the World's Healthiest Foods' recipes containing these foods will appear immediately below.


Bioflavonoids


Bioflavonoids are a diverse group of substances naturally found in a wide variety of fruits and vegetables. Certain bioflavonoids, like quercitin, which can be found in cherries, white grapefruit, apples, pears, grapes, cranberries, red onions, yellow onions, green cabbage, spinach, kale, and garlic, have been shown to decrease the rates of colon cancer in some animal studies. Although these substances have only been used in animal studies so far, they show potential in possibly being useful to help decrease colon cancer in humans as well.


Specific Foods That May Help Decrease Risk


Vegetables


A high intake of vegetables has been shown in numerous studies to be one of the best means of decreasing colon cancer risk. Many studies have shown that people who consume a diet high in vegetables have much lower rates of colon cancer than those who don't eat a diet rich in these foods.


A Swedish study, conducted by researchers at the Karolinska Institutet and involving more than 82,000 men and women with an average follow up of 7.2 years, clearly shows that making vegetables a daily staple in your healthy way of eating can greatly reduce your risk of developing stomach (gastric) cancer— the fourth most common cancer world-wide, and the most common cancer in Japan. (Larsson SC, Bergkvist L, et al. Cancer Epidemiol Biomarkers Prev.)


Study participants who consumed at least 2.5 servings per day of vegetables had a 44% reduced risk of stomach cancer, compared to those eating less than 1 serving per day.


Those who consumed at least 3 servings per week of green leafy vegetables showed a 46% reduction in gastric cancer risk, compared to those who ate less than a half-serving of green leafy vegetables per week. Those eating at least 3 weekly servings of root vegetables did even better with a 67% reduced risk of gastric cancer, compared to those who ate less than a half-serving per week of root vegetables.


Vegetables tend to be very high in many nutrients that have been shown to be beneficial for preventing colorectal cancer, including fiber, folate, vitamin C, beta-carotene, and a wide variety of bioflavonoids. They also contain other substances which have been shown to increase the ability of the body to inactivate harmful carcinogenic chemicals.


Unfortunately, studies show that 80% of American children and 68% of American adults don't get their recommended 5 servings of fruits and vegetables every day. Increasing vegetable intake in general could go a long way towards helping reduce the risk of colorectal cancer, as well as many other diseases.


Specific types of vegetables that have been shown to be especially helpful in the prevention of colon cancer include:


Brassicas


The term 'brassica' refers to a group of vegetables that includes cabbage, kale, broccoli, cauliflower, brussel sprouts, kohlrabi, turnips, and rutabagas. These vegetables have certain substances in them known as isothiocyanates and indoles, which have been shown in research studies to be especially good for protecting cells against the effects of carcinogens and also for decreasing tumor development in the colon. Some studies show that eating just two or more servings of these vegetables a week can decrease colon cancer risk by 20-40%.


A study published in the April 2004 issue of Carcinogenesis explains at least some of the reasons why eating cruciferous vegetables such as broccoli, cauliflower, cabbage and Brussels sprouts is associated with a reduction in colorectal cancer risk. It appears that when we eat crucifers, the amounts of certain liver enzymes necessary for the detoxification and clearance of carcinogens, such as the heterocyclic amines found in cooked foods, particularly red meat, are greatly increased. In this study, subjects avoided crucifers for 12 days (Period 1), ate broccoli and Brussels sprouts daily for 12 days (Period 2), and again avoided crucifers for 12 days (Period 3). At the end of each 12 day period, subjects ate a cooked meat meal containing heterocyclic amines. Consumption of cruciferous vegetables increased study subjects' ability to detoxify and excrete heterocyclic amines to 127% and 136% of levels seen in Periods 1 and 3, respectively.
The liver usually clears potentially harmful compounds using two metabolic pathways: Phase 1, which uses the Cytochrome P450 family of enzymes, and Phase 2, in which compounds activated in Phase 1 are conjugated (joined) with carrier molecules and ferried out of the body. In this study, the researchers found that activity in important parts of both Phase I and Phase 2 (specifically, the Phase I liver detoxification enzyme CYP1A2, and the Phase II glucuronidation conjugation pathway) was significantly increased when broccoli and Brussels sprouts were eaten daily.


In another study,researchers in the Netherlands investigated the effect of a diet high in Brussels sprouts on DNA damage. They compared two groups of healthy male volunteers. Five men ate a diet that included 300 g (about 10 ounces) of cooked Brussels sprouts daily, while the other five men at a diet free of cruciferous vegetables. After three weeks, the group that ate Brussels sprouts had 28% decrease in measured DNA damage. Reduced DNA damage may translate to a reduced risk of cancer since mutations in DNA allow cancer cells to develop.


Sulforaphane, which is formed when cruciferous vegetables are chopped or chewed, is already known to trigger the liver to produce enzymes that detoxify cancer-causing chemicals, inhibit chemically-induced breast cancers in animal studies, and induce colon cancer cells to commit suicide. A study published in the September 2004 issue of the Journal of Nutrition has also shown that sulforaphane helps stop the proliferation of breast cancer cells, even in the later stages of their growth.


New research has greatly advanced scientists' understanding of just how Brassica family vegetables such as cabbage, cauliflower, broccoli, kale and Brussels sprouts help prevent cancer. When these vegetables are cut, chewed or digested, a sulfur-containing compound called sinigrin is brought into contact with the enzyme myrosinase, resulting in the release of glucose and breakdown products, including highly reactive compounds called isothiocyanates. Isothiocyanates are not only potent inducers of the liver's Phase II enzymes, which detoxify carcinogens, but research recently conducted at the Institute for Food Research in the U.K. shows one of these compounds, allyl isothicyanate, also inhibits mitosis (cell division) and stimulates apoptosis (programmed cell death) in human tumor cells.


Cell replication (when the parent cell divides to form two daughter cells) occurs in a four-stage process. After the cell divides (the first stage), pole structures are created called spindles (the second or metaphase). If anything interferes with the construction and deconstruction of these spindles, the cell division process stops, and the damaged cells commit suicide. In research published in Carcinogenesis, the IFR team, led by Ian Johnson, has shown that sulforaphane disrupts the metaphase, thus preventing the cell division of the colon cancer cells.


Sulforaphane may also offer special protection to those with colon cancer-susceptible genes, suggests a study conducted at Rutgers University and published online on May 4, 2006, in the journal Carcinogenesis.


In this study, researchers sought to learn whether sulforaphane could inhibit cancers arising from one's genetic makeup. Rutgers researchers Ernest Mario, Ah-Ng Tony Kong and colleagues used mice bred with a genetic mutation that switches off the tumor suppressor gene known as APC, the same gene that is inactivated in the majority of human colon cancers. Animals with this mutation spontaneously develop intestinal polyps, the precursors to colon cancer.


The mice were divided into three groups. One group of animals were fed diets supplemented with 300 parts per million (ppm) of sulforaphane. A second group received a diet supplemented with 600 ppm sulforaphane for three weeks. The third group, which served as a control, received unsupplemented diets. At the end of the three week period, mice fed the diet enhanced with the lower dose sulforaphane had 25% fewer polyps, and those who received the higher dose had 47% percent fewer polyps than the control mice. In addition, in the mice fed diets containing sulforaphane, the tumors were smaller, growing more slowly and with higher apoptotic (cell suicide) indices. The researchers found that sulforaphane suppressed enzymes called kinases that are expressed not only in mice, but also in humans, with colon cancer.


Alliums


"Alliums" refers to a group of vegetables that includes onions, garlic, leeks, chives, scallions, and shallots. Just two or more servings per week can help to reduce the risk of colon cancer. These vegetables are rich sources of substances called organosulfur compounds, or OSCs.


These OSCs have been shown to have anti-cancer activities that act at every stage in the initial development and progression of cancer. They increase the body's ability to break down harmful chemicals. They're also good at protecting against the effects of carcinogens, particularly of heterocyclic amines, which are formed in the high-heat cooking of meats.


Cooking meat with onions, for example, has been shown to decrease the ability of the cooked meat to cause DNA damage. Since the beneficial substances in these foods tend to break down over time, fresh onions and garlic are much better for reducing the negative effects of carcinogens than just the oils or dried forms of the vegetables.


Onions and Garlic Protective against Many Cancers


Making onions and garlic a staple in your healthy way of eating may greatly lower your risk of a number of common cancers, including colorectal cancer, suggests a large data set of case-control studies from Southern European populations (Galeone C, Pelucchi C et al, American Journal of Clinical Nutrition).


Study participants consuming the most onions showed a 56% reduced risk for colorectal cancer, plus an 84% reduced risk for cancer of the oral cavity and pharynx, 88% reduced risk for esophageal cancer, 83% reduced risk for laryngeal cancer, 25% reduced risk for breast cancer, 73% reduced risk for ovarian cancer, 71% reduced risk for prostate cancer, and 38% reduced risk for renal cell cancer, compared to those eating the least onions.


Similarly, those eating the most garlic had a 26% reduced risk for colorectal cancer, plus a 39% reduced risk for cancer of the oral cavity and pharynx, 57% reduced risk for esophageal cancer, 44% reduced risk for laryngeal cancer, 10% reduced risk for breast cancer, 22% reduced risk for ovarian cancer, 19% reduced risk for prostate cancer, and 31% reduced risk for renal cell cancer, compared to those eating the least garlic.


Soy Foods


A substance found in soybeans may reduce colon cancer risk, suggests animal research conducted by Alfred Merrill at Emory University and the Karmanos Cancer Institute.


The cancer-protective substance is a sphingolipid (a type of lipid or fat that, in the body, is primarily used as a constituent of nerve tissue) called soy glucosylceramide. Sphingolipids found in milk have already been shown to inhibit the formation of tumors in mice exposed to carcinogens known to cause colon cancer. While the sphingolipids found in soy differ structurally from those found in milk, the soy compounds had comparable effects.


When mice exposed to a carcinogen were given a diet containing 1% soy glucosylceramide, the proliferation of colon cancer cells dropped by 56%. When the same diet was given to a strain of mice bred to spontaneously develop colon cancer, the rate at which tumors formed dropped 37%.


Soy sphingolipids provided this protection by affecting the expression 96 different genes in the cells that form the lining of the intestines, increasing 32 and decreasing 64. Soy's effects on these genes resulted in a decrease in the production of two factors associated with cancer initiation and promotion: hypoxia-induced factor 1 alpha and transcription factor 4.


While other plants also contain sphingolipids, soy contains relatively high amounts of glucosylceramide, which researchers think may be one reason for the cancer-preventive effects of eating soy foods.


Carrots


Although best known for their high content of beta carotene, carrots also contain a phytonutrient called falcarinol that may be responsible for the recognized epidemiological association between frequently eating carrots and a reduced risk of cancers.


Falcarinol provides protection against colon cancer, suggests a study published in the February 2005 issue of the Journal of Agricultural and Food Chemistry. Three groups of rats in whom precancerous colon lesions (aberrant crypt foci) had been chemically-induced were fed a standard diet, one supplemented with freeze-dried carrots naturally containing falcarinol, or one supplemented with an extract of falcarinol. After 18 weeks, precancerous lesions in the animals given diets containing carrots or falcarinol were much smaller than those in the control animals, and far fewer of the lesions had grown in size or progressed to become tumors.


Fruits


A high intake of fruits has been associated with a decreased risk for colon cancer in several studies. Fruits, like vegetables, contain other beneficial nutrients including fiber, vitamin C, folate, carotenoids, and bioflavonoids. The current recommendation is that people get at least 5 servings of fruits and vegetables every day. It's best to consume whole fruits instead of just juices since juices don't usually have all of the fiber and nutrients of the whole fruit. Also, variety is the key to making sure that the diet contains many different nutrients and bioflavonoids.


Apples


In a study published in the March 2005 issue of Molecular Nutrition and Food Research, a polyphenol-rich extract of an apple juice blend powerfully inhibited the growth of human colon cancer cells in the laboratory.


However, when researchers put together a mixture containing only the bioactive compounds identified in apple juice so far (which included its proanthocyanidins and quercetin), the mixture was ineffective in inhibiting the growth of colon cancer cells.


They concluded that as yet unknown constituents contribute to apples' potent protective qualities. The conclusion we draw at the World's Healthiest Foods is that it is not single nutrients, but their synergy in whole, natural foods that is the source of their effectiveness in promoting health. Because apples are so richly endowed with phytonutrients capable of strong antioxidant and anticancer activities and are so universally enjoyed, eating an apple (or two) a day may be effective (and we'd add easy and inexpensive) way to lessen the incidence of colon cancer.


Cranberries


The compounds found in cranberries that help prevent urinary tract infections may also help prevent cancer, suggests research conducted at the University of Massachusetts-Dartmouth and reported in the online edition of the Journal of the Science of Food and Agriculture, October 17, 2005.


Researchers isolated active cranberry compounds, called proanthocyanidins, then tested them on several tumor cell lines. Cranberry proanthocyanidins inhibited the growth of all the cancers—human lung, colon and leukemia cells—in culture, without affecting healthy cells.


In other studies, proanthocyanidins from grapeseed have been linked to cancer inhibition, but the structure of the proanthocyanidins in cranberries is significantly different from those found in other berries.


Unlike most fruit, cranberries contain proanthocyanidins with A-type linkages between units, a structural feature identified in cranberry proanthocyanidins with antibacterial adhesion properties and those with LDL-protective properties, explained lead researcher, Catherine Neto.


Cranberries' proanthocyanidins unique characteristics may translate into a superior ability to prevent cancer. This study showed significant inhibition of cancer cell proliferation, not previously shown with other proanthocyanidins, as well as the blocking of tumor growth.


The protective activity occurred at no less than 100ug/mL concentration. "It's hard to say whether you would get these levels distributed to different tissues to the extent where you would have activity in vivo, but eating cranberries could be helpful," said Neto. "There are so many compounds in cranberries capable of having some anti-cancer mechanism that when taken together there is potential for benefit," she added.


Blueberries


Laboratory studies published in the September 2005 issue of the Journal of Agricultural and Food Chemistry show that phenolic compounds in blueberries can inhibit colon cancer cell proliferation and induce apoptosis (programmed cell death).


Extracts were made of the blueberry phenols, which were freeze-dried and further separated into phenolic acids, tannins, flavonols, and anthocyanins. Then the dried extracts and fractions were added to cell cultures containing two colon cancer cell lines, HT-29 and Caco-2.


In concentrations normally found in rat plasma after eating blueberries, anthyocyanin fractions increased DNA fragmentation (a sign that apoptosis or cell death had been triggered) by 2-7 times. Flavonol and tannin fractions cut cell proliferation in half at concentrations of 70-100 and 50-100 microg/mL, while the phenolic fraction was also effective, but less potent, reducing proliferation by half at concentrations of 1000 microg/mL. Bottomline: eating blueberries may reduce colon cancer risk.


Grapes and Red Wine


Drinking at least three glasses of red wine a week could cut the risk of colorectal cancer by almost 70%, researchers reported at the 71st Annual Scientific Meeting of the American College of Gastroenterology in Las Vegas. Colorectal cancer accounts for 9% of new cancer cases every year worldwide, occurring primarily in the United States and Europe. Fortunately, if diagnosed early, it remains one of the most curable cancers.


Joseph Anderson and colleagues from the Stony Brook University in New York looked at the drinking habits of 360 red and white wine drinkers with similar lifestyles and found that, while white wine consumption had no association with colorectal cancer occurrence, regularly drinking red wine was linked to a 68% reduced risk of the cancer.


The active component in wine thought to be largely responsible is resveratrol, a natural anti-fungal that grapes—especially organically grown red grapes— produce under their skin. The concentration of resveratrol is significantly higher in red than white wine because the skins are removed earlier during white-wine production.


Nearly all dark red wines—merlot, cabernet, zinfandel, shiraz and pinot noir—contain resveratrol, although the amount in a bottle can range from 0.2 to 5.8 milligrams per litre, varying among types of grapes and growing seasons.


Also, grapes and wine are reported to contain more than 600 different phytonutrients, including many with antioxidant activity, so it's likely that a number of compounds in grapes, including resveratrol, work synergistically to protect against colorectal cancer.


In support of this hypothesis, a recent animal study by researchers from Tuft's University reported brain-protecting effects from Concord grape juice resulting from synergistic activity among grape polyphenols. "It may be that the whole is greater than the sum of its parts," wrote lead author of this study, Barbara Shukitt-Hale, in the journal Nutrition.


In other research—a meta-analysis of 34 studies involving over a million people published in the Archives of Internal Medicine—investigators at the Catholic University of Campobasso in Italy concluded that moderate drinking is associated with a reduction in all-cause mortality.


Although excessive alcohol consumption was shown to increase mortality, drinking 2 to 4 drinks per day was associated with a reduction in deaths from all causes in men. For women, the protective effect ended above 2 drinks per day.


It's been proposed that the protective effect of moderate drinking may be due to associated lifestyle factors, but lead author of this study, Di Castelnuovo noted, "We've carefully examined this aspect. Our data suggest that, even considering all main confounding factors (as dietary habits, physical activity or the health of people studied), a moderate consumption of alcoholic beverages keeps on showing a real positive effect."


The review also determined that the protective benefit of alcohol is greater for European than American men, which could be explained by the way in which alcohol is consumed: European men are likelier than Americans to drink wine and to enjoy it with a meal.


"The core of this study is not just about alcohol," Catholic University Research Laboratories director Giovanni de Gaetano stated. "It is also the way we drink that makes the difference: little amounts, preferably during meals, this appears to be the right way. This is another feature of the Mediterranean diet, where alcohol, wine above all, is the ideal partner of a dinner or lunch, but that's all: the rest of the day must be absolutely alcohol-free. The message carried by scientific studies like ours is simple: alcohol can be a respectful guest on our table, but it is good just when it goes with a healthy lifestyle, where moderation leads us toward a consumption inspired by quality not by quantity."


Recent Harvard research (the Northern Manhattan Study and the Cardiovascular Health Study) also suggest that moderation in alcohol consumption is key: lowest risk of stroke was seen in those who had one, or maybe two, drinks a day.


If you're inspired to try a daily glass of red wine as part of your healthy way of eating, you may want to look for red wine from southwestern France or Sardinia. Research published in Nature suggests that the protective polyphenols in red wine are present at higher concentrations in wines from southwestern France and Sardinia, where traditional production methods ensure these compounds are efficiently extracted during wine production.


In this study, researchers evaluated red wine samples from Australia (14), France (11), Greece (16), Italy (3), Spain (1), Sardinia (15), Argentina (33), Chile (9), Bolivia (5), Uruguay (4), and the USA (14 from California), along with various other wines from Southwest France, Georgia and South Africa.


They also looked at human aging patterns using data from the 1999 French census. The data showed six regions in Southwest and Central France with >25% higher level of men aged 75 or more, compared to the national average. Men living in Nuoro province in Sardinia also had higher longevity. (The analyses focused on men because they have been shown to benefit more than women from regular wine consumption.) Wines produced in areas of increased longevity (e.g., the Gers area of France and Nuoro province in Sardinia) were found to have 2-4-fold more polyphenol (oligomeric procyanidins or OPCs) content and biological activity than wines from other regions. These are areas where traditional wine making methods are still used, plus the Tannat grape used in these regions is also particularly high in OPCs.


Regular Green Tea Drinking Cuts Colorectal Cancer Risk in Half


To evaluate the link between green tea consumption and colorectal cancer risk, researchers followed 69,710 Chinese women ranging in age from 40 to 70 for 6 years.


Women who regularly drank green tea when the study began were 37% less likely to develop colorectal cancer compared to infrequent green tea drinkers. Women who continued to drink green tea regularly throughout the study fared even better, reducing their risk of colorectal cancer by 57%.: Cancer Epidemiol Biomarkers Prev. 2007 Jun;16(6):1219-23..


Practical Tip: Enjoy green tea as both a hot and iced beverage.


Brew green tea with thinly sliced ginger and lemon, or sprigs of spearmint. Add one teaspoon of honey per cup, stir and serve hot, or use half the amount of hot water (or twice the amount of tea), allow the tea to brew and cool, then combine half and half with fruit juice, such as peach, pineapple or papaya. Blend and pour over ice.
Make green tea chai by brewing green tea in hot vanilla soy milk. Top with a dash each of cinnamon, black pepper, ginger and allspice.
Whole Grains


Whole grains are also an excellent source of nutrients like fiber, the B-vitamins, and something called phytic acid. Phytic acid, also called phytate, is a substance found in many types of whole grains, especially wheat bran and oat. It has been shown in a number of studies to inhibit the formation of tumors in the colon and other locations, to increase apoptosis of mutated cells, and to reduce tumor growth. It's also found in high quantities in legumes, including beans and peas.


It's important that people get plenty of these foods in their diet in order to reduce the risk of colon cancer. Phytic acid can also bind together with certain minerals, however, to lower their absorption; so consumption of these phytate-containing whole foods should always be part of a balanced, varied, whole foods diet.


Cold Water Fish


As mentioned earlier, several studies have shown that populations that consume a good amount of fish have very low rates of colon cancer. This may be due mainly to the omega-3 fatty acids, such as EPA and DHA, found in fish. While other types of meat, particularly red meat, has been shown to increase colon cancer risk, fish intake has been shown to be protective. The best types of fish to consume are the cold-water fish, like salmon, mackerel, herring, and cod, as they are richest in the beneficial omega-3 oils.


Olive Oil


While overconsumption of certain types of fats, including omega-6 fats found in certain vegetable oils and saturated fats found in animal products, has been shown to increase the risk of colon cancer, monounsaturated fats, such as those found in olive oil, have been shown to be protective when consumed in appropriate amounts.
As noted above in the discussion of Calcium and Vitamin D under Nutrient Needs, a study published in the August 2003 issue of Carcinogenesis suggests that olive oil is particularly protective in individuals whose meals include red meat. This is because olive oil is less susceptible to oxidation than most other types of fat and is therefore less likely to be damaged by the form of iron in red meat, haemin, which by promoting free radical formation and activity, increases the cellular damage that ultimately results in colon cancer.
Populations such as those in the Mediterranean area which have relatively high intakes of olive oil typically have fairly low levels of colon cancer. Other substances found in olive oil, such as squalene and lignans, have also been shown to reduce colon cancer formation.


Phenols in virgin olive oil can inhibit several stages through which normal cells are transformed into cancerous ones in the colon, show test tube studies published in the October 2005 issue of Carcinogenesis
In this research, phenols extracted from virgin olive oil were used in a series of cell cultures modeling important stages of colon cancer development. When pre-incubated with olive oil phenols for 24 hours before being exposed to damaging hydrogen peroxide, human colon cells were much more resistant to DNA damage.


After 48 hours incubation with olive oil phenols, the membrane surrounding human colon cells was much more resistant to invasion by a highly aggressive strain of human colorectal cancer (cell line HT115). To retain the most phenols in your olive oil, minimize the oil's exposure to light and heat. Purchase oil in an opaque container, store in a dark cupboard, and add to foods after cooking.


Peanuts Protective, but Pickled Foods Increase Risk of Colon Cancer


A number of studies have shown that nutrients found in peanuts, including folic acid, phytosterols, phytic acid (inositol hexaphosphate) and resveratrol, may have anti-cancer effects. A good source all these nutrients—including the phytosterol beta-sisterol, which has demonstrated anti-cancer actions—peanuts have long been considered a likely candidate as a colon cancer-preventive food.


Colorectal cancer is the second most fatal malignancy in developed countries and the third most frequent cancer worldwide. In Taiwan, not only has incidence of colon cancer increased, but the likelihood of dying from the disease rose 74% from 1993 to 2002.


Taiwanese researchers decided to examine peanuts' anti-colon cancer potential and conducted a 10-year study involving 12,026 men and 11,917 women to see if eating peanuts might affect risk of colon cancer.(Yeh CC, You SL, et al., World J Gastroenterol)


Researchers tracked study participants' weekly food intake, collecting data on frequently consumed foods and folk dishes such as sweet potato, bean products, peanut products, pickled foods, and foods that contained nitrates or were smoked.


Risk of colon cancer was found to be highly correlated with both peanuts, which greatly lessened risk, and pickled foods, which greatly increased risk, particularly in women.


Eating peanuts just 2 or more times each week was associated with a 58% lowered risk of colon cancer in women and a 27% lowered risk in men.


In women, but not in men, eating pickled foods 2 or more times a week more than doubled the likelihood of developing colon cancer risk for women, increasing their risk 215%.


Practical Tips: To help prevent colon cancer, avoid pickled foods, but enjoy peanuts at least twice each week. In addition to that old stand-by, the PB&J sandwich, try some of the following:


Spread peanut butter on your morning waffle, whole grain toast or mid-morning crackers.
Add a tablespoon of peanut butter to your morning smoothie.
Enjoy a handful of dry roasted peanuts with a glass of tomato juice as an afternoon snack.
Combine peanut butter, coconut milk, and ready-to-use Thai red or green curry paste for a quick, delicious sauce. Pour over healthy sautéed vegetables. Use as a cooking sauce for organic tofu or salmon.
Toss cooked brown rice with sesame oil, chopped peanuts, scallions, sweet red pepper, parsley and currants.
When purchasing peanut butter, be sure to read the label. Hydrogenated(trans-) fats and sugar are often added to peanut butter. Buy organic and choose brands that contain peanuts, salt—and nothing else!
Turmeric


Turmeric is a seasoning rich in a phytonutrient known as curcumin. Curcumin has been shown in several research studies to have very strong antioxidant and anti-inflammatory actions in the body. In addition, it has been shown to decrease the excessive cell proliferation and to increase the apoptosis of mutated cells. In general, some studies have shown that it may be useful in reducing the formation of colon tumors and the development of colon cancer.
Turmeric and Onions May Help Prevent Colon Cancer


Curcumin and quercitin, an antioxidant in onions, reduce both the size and number of precancerous lesions in the human intestinal tract, shows research published in the August 2006 issue of Clinical Gasteroenterology and Hepatology.


Five patients with an inherited form of precancerous polyps in the lower bowel known as familial adenomatous polyposis (FAP) were treated with regular doses of curcumin and quercetin over an average of six months. The average number of polyps dropped 60.4%, and the average size of the polyps that did develop dropped by 50.9%.


FAP runs in families and is characterized by the development of hundreds of polyps (colorectal adenomas) and, eventually, colon cancer. Recently, nonsteroidal anti-inflammatory drugs (NSAIDs such as aspirin, ibuprofen) have been used to treat some patients with this condition, but these drugs often produce significant side effects, including gastrointestinal ulcerations and bleeding, according to lead researcher Francis M. Giardiello, M.D., at the Division of Gastroenterology, Johns Hopkins University.


Previous observational studies in populations that consume large amounts of curry, as well as animal research, have strongly suggested that curcumin, one of the main ingredients in Asian curries, might be effective in preventing and/or treating cancer in the lower intestine. Similarly, quercetin, an anti-oxidant flavonoid found in a variety of foods including onions, green tea and red wine, has been shown to inhibit growth of colon cancer cell lines in humans and abnormal colorectal cells in animals.


In this study, a decrease in polyp number was observed in four of five patients at three months and four of four patients at six months.


Each patient received curcumin (480 mg) and quercetin (20 mg) orally 3 times a day for 6 months. Although the amount of quercetin was similar to what many people consume daily, the curcumin consumed was more than would be provided in a typical diet because turmeric only contains on average 3-5 % curcumin by weight.


While simply consuming curry and onions may not have as dramatic an effect as was produced in this study, this research clearly demonstrates that liberal use of turmeric and onions can play a protective role against the development of colorectal cancer. And turmeric doesn't have to only be used in curries. This spice is delicious on healthy sautéed apples, and healthy steamed cauliflower and/or green beans and onions. Or, for a flavor-rich, low-calorie dip, try adding some turmeric and dried onion to creamy yogurt.


Ginger


Gingerols, the main active components in ginger and the ones responsible for its distinctive flavor, may also inhibit the growth of human colorectal cancer cells, suggests research presented at the Frontiers in Cancer Prevention Research, a major meeting of cancer experts that took place in Phoenix, AZ, October 26-30, 2003.


In this study, researchers from the University of Minesota's Hormel Institute fed mice specially bred to lack an immune system a half milligram of -gingerol three times a week before and after injecting human colorectal cancer cells into their flanks. Control mice received no -gingerol.


Tumors first appeared 15 days after the mice were injected, but only 4 tumors were found in the group of -gingerol-treated mice compared to 13 in the control mice, plus the tumors in the -gingerol group were smaller on average. Even by day 38, one mouse in the -gingerol group still had no measurable tumors. By day 49, all the control mice had been euthanized since their tumors had grown to one cubic centimeter (0.06 cubic inch), while tumors in 12 of the -gingerol treated mice still averaged 0.5 cubic centimeter—half the maximum tumor size allowed before euthanization.


Research associate professor Ann Bode noted, "These results strongly suggest that ginger compounds may be effective chemopreventive and/or chemotherapeutic agents for colorectal carcinomas."


In this first round of experiments, mice were fed ginger before and after tumor cells were injected. In the next round, researchers will feed the mice ginger only after their tumors have grown to a certain size. This will enable them to look at the question of whether a patient could eat ginger to slow the metastasis of a nonoperable tumor. Are they optimistic? The actions of the University of Minnesota strongly suggest they are. The University has already applied for a patent on the use of -gingerol as an anti-cancer agent and has licensed the technology to Pediatric Pharmaceuticals (Iselin, N.J.).


Yogurt


Some studies have shown that populations that consume high levels of yogurt and other fermented dairy products have a lower rate of colon cancer than other populations. Fermented dairy products are rich in certain types of beneficial bacteria, which normally live in the human intestines. These bacteria have been shown to protect colon cells from the damaging effects of carcinogens. These bacteria also bind to the hazardous heterocyclic amines in meats, thereby reducing their contact with the cells of the colon and rectum.


Harmful bacteria in the colon can actually activate some carcinogens, making them more dangerous to the body than they were before. Beneficial bacteria compete with and can reduce the numbers of these harmful bacteria, thereby protecting the body from these additional carcinogens. It's important that the yogurt and other products contain live, active culture. For people who cannot tolerate or prefer not to consume dairy products, several types of soy yogurts are now available.


In addition to yogurt, consuming full-fat dairy foods such as whole milk, kefir, cheese, cream, sour cream and butter may significantly reduce risk for colorectal cancer, suggests a study published in the October 2005 issue of the American Journal of Clinical Nutrition.


Although high in saturated fat, these dairy foods contain a number of potentially cancer-preventive factors, including a protective fat called conjugated linoleic acid (CLA), which has also been shown to be cardioprotective.


In this study, 60,708 women aged 40-76 years were followed during an average of 14.8 years. Those women who ate at least 4 servings of high fat dairy foods each day were found to have a 41% lower risk of colorectal cancer compared to women eating less than a serving of high-fat dairy foods daily.


For each increment of 2 servings of high-fat dairy foods a woman consumed each day, her risk of colorectal cancer dropped 13%. So, while research continues to indicate that it is wise to limit your intake of saturated fat by cutting back on servings of high-fat meats, enjoying full-fat versions of dairy products may actually be protective.


Nutrient Excesses


Substances to Avoid


Fat


Many studies have shown a relationship between the amount of fat consumed and the risk of colon cancer. Those who consume large amounts of fat in their diets may have twice the risk of developing colon cancer compared to those who consume low-fat diets.


Since bile is needed for the proper breakdown and digestion of fats, a high intake of fat leads to an increased production of bile and bile salts, which can be carcinogenic to the cells of the colon. The types of fats that seem to present the greatest problems when consumed in excessive amounts are saturated fats, found mostly in animal products like meat and eggs, and omega-6 fats, found mostly in vegetable oils and margarines.


Omega-6 fats are especially prone to the negative effects of free radicals. Once oxidized by free radicals, these fats can lead to DNA damage and eventually to cancer growth and spread. Reducing the overall amount of fat in the diet and balancing the type of fat by including oils such as olive oil and fish oils, can really help to decrease the risk of colon cancer.


Meat


Several studies have shown that high intakes of meats, particularly red meats and processed meats, are associated with an increased risk of colon cancer. Poultry, fish and other sources of protein, such as legumes, are not associated with an increased risk and may actually help to lower risk.


The most detrimental type of meat that can be consumed is meat that has been cooked at a high temperature, such as barbequed, grilled, charcoal-grilled, broiled, and fried. High temperature cooking of meats, including red meat, poultry, and fish, leads to the production of chemicals called heterocyclic amines, which are very potent carcinogens to the cells of the colon and rectum.


Direct flame-grilling and smoking produces another type of carcinogen, called polycyclic aromatic hydrocarbons, which may be just as bad. These chemicals can be avoided by cooking meats at lower temperatures through stir-frying, baking, or poaching, and also by cooking meats with foods that contain antioxidant bioflavonoids, such as garlic, onions, apples, or soy products.


Overeating


Overeating in general has been linked to an increased risk for colon cancer. People who consume lower calorie diets seem to have a lower risk of developing colon cancer than those who consume more calories than they need. Switching from a diet high in refined foods or animal products to one that is high in whole grains, fruits, vegetables, legumes, and fish can usually help to reduce calorie intake.


Sugar


One large study showed that people who consumed the largest amounts of refined sugar, or sucrose, had an increased risk of colon cancer compared to those who consumed less. Sugar has many negative effects on the body, including decreasing the proper function of the immune system. Although the exact mechanism whereby sugar may increase colon cancer is not currently known, it may have something to do with an inability of the immune system to detect and destroy cancer cells in those who consume a lot of refined sugar.


Alcohol


Many studies have shown a strong association between regular intake of alcoholic beverages and an increased risk of colon cancer, and particularly rectal cancer. The risk seems to be the greatest with beer consumption, though some studies show a link with wine and alcohol in general. The negative effects of alcohol are greatest in people who also have a low intake of folate, so people who continue to have some alcohol in their diets need to be sure that they're consuming enough dietary folate. In general, though, those at risk for the development of colorectal cancer should greatly limit their use of alcohol products.


Pickled Foods


When Taiwanese researchers conducted a 10-year study involving 12,026 men and 11,917 women to see if eating peanuts might affect risk of colon cancer, they discovered that while peanuts greatly lessened risk, pickled foods greatly increased it, particularly in women.(Yeh CC, You SL, et al., World J Gastroenterol)


Eating peanuts just 2 or more times each week was associated with a 58% lowered risk of colon cancer in women and a 27% lowered risk in men.


In women, but not in men, eating pickled foods 2 or more times a week more than doubled the likelihood of developing colon cancer risk for women, increasing their risk 215%.


Recommended Diet


Women who choose the naturally low glyceimc (GI) healthy way of eating suggested on the World's Healthiest Foods are much less likely to develop colorectal cancer compared to women whose diet is largely composed of sugar-rich, fiber-poor foods.


Researchers are beginning to think that a diet high glycemic load (i.e., a diet high in sugars and refined carbohydrates), which results in high blood sugar and a drop in our cells' ability to respond to insulin (insulin resistance), may also create an internal environment that promotes tumor growth. Data from a 7.9 year study involving 38,451 women aged 45 or older from the Women's Health Study that was published in the February 2004 issue of the Journal of the National Cancer Institute, shows that a high glycemic load diet is statistically significantly associated with the development of colon cancer, increasing risk by a whopping 285%! Glycemic index (GI) is a system that ranks foods based on their immediate effect on raising blood sugar levels. A low GI food will cause a small rise in blood sugar levels, whereas a high GI food can trigger a large and rapid increase. Glycemic load (GL) is calculated by multiplying the amount of carbohydrate in a serving by the GI and dividing by 100. Basically, only a few whole foods such as potatoes and bananas have a high GI, and even these can safely be part of the healthy way of eating recommended on the World's Healthiest Foods. Highly processed, refined sugar-laden foods, however, have a very high GI and GL. For a full explanation of GI and GL, including a guide to the GI of the World's Healthiest Foods, just click What is the Glycemic Index


So why should a high GI /GL diet increase colorectal cancer risk? Researchers think a high GL increases insulin-like growth factors, which could promote out of control cell replication or levels of C-reactive protein, an inflammatory compound that, in high amounts, could exacerbate pro-inflammatory responses, either locally or systemically. Regardless of the mechanism involved, a high GL diet clearly increases risk of colorectal cancer—yet another good reason to choose the delicious and low GL way of eating our recipes and meal planners offer. (March 25, 2004)


Need more evidence to convince you to try the healthy, low glycemic load way of eating recommended on the World's Healthiest Foods? A study published in the April 2004 issue of the Journal of the National Cancer Institute has found yet another indication of the strong link between the high gylcemic diet that leads to insulin resistance and diabetes and a significantly increased risk of colorectal cancer.


Researchers at Brigham and Women's Hospital and Harvard Medical School in Boston followed 14,916 male physicians for 13 years. The men with the highest blood levels of C-peptide—a hormone that reflects insulin levels, so higher C-peptide levels indicate higher levels of insulin in the blood—had a 2.7 times the risk (that's a 270% increase in risk!) of developing colon and rectal cancers compared to men with the lowest levels.


The researchers note that a diet high in calories and animal fat and low in fiber, along with lack of exercise, promotes not only insulin resistance and type 2 diabetes, but also colorectal cancer.


Lowering your C-peptide levels and risk of type 2 diabetes and colorectal cancer is not only easy, but delicious—just rely on the outstanding recipes created to help you enjoy your food and your health by George Mateljan. Pressed for time? Use any of the many recipes George has carefully crafted to take just 15 minutes to prepare. (May 6, 2004)


Perhaps the best diet for reducing the risk of colorectal cancer is one that is high in vegetables, fruits, especially grapefruit (October 19, 2004), whole grains, cold-water fish, fermented dairy products like yogurt, and legumes, especially soyfoods.


A study published in the January 2004 issue of the Journal of Nutrition suggests that colon cancer may be a hormone-responsive cancer, and that soy protein can not only help prevent its occurrence but can have a very positive effect on the number and size of tumors that do occur. In this study, female mice whose ovaries had been removed to limit their sources of estrogen were exposed to an agent that causes colon tumors, then fed five different diets designed to compare the effects of specific ingredients, and followed for a year.


Diet One contained milk protein, and Diet Two, soy protein with no isoflavones; both these diets were free of any kind of estrogen. The remaining three diets contain soy protein plus an estrogenic component. Diet Three contained soy protein and the isoflavone, genistein, a phytoestrogen found in soy. Diet Four contained soy plus a mixture of soy-derived isoflavones including genistein, and Diet Five contain estrone, a naturally occurring human estrogen.


While the diet containing estrone was the most effective in preventing colon cancer, all the soy/estrogen diets were also protective and even those mice given soy protein with no estrogen-like factors that did develop colon cancer had fewer and smaller tumors compared to mice given milk protein. Lead researcher, Ruth MacDonald, professor of food science at the University of Missouri, is now trying to determine how soy compounds protect against colon cancer. Until this work is done, however, she notes that not only is soy protein thought to also be helpful in the prevention of heart disease, but "the good news is that there are many ways to add soy to your diet now, and we know of no harmful side-effects to eating soy protein." (March 25, 2004)


The consumption of saturated fats, from food like meats and eggs, should be limited. Red meat and processed meats should be replaced by other protein sources, such as poultry, cold water fish, such as salmon, mackerel, herring, and cod, and legumes, especially soybeans, and all meats should be cooked at lower temperatures through stir-frying, baking, or poaching, and not cooked at high temperatures through grilling, charcoal-grilling, barbequing, broiling, or frying.


When eating meat, cooking with foods such as onions, garlic, apples, or soy products like miso is also recommended.


Omega-6 fats, found in vegetable oils and margarines, should be limited and accompanied by use of oils like olive oil.


Brassica vegetables, such as broccoli, cauliflower, turnips, brussel sprouts, rutabaga, cabbage, kale, and kohlrabi, and allium vegetables, such as onions, garlic, chives, shallots, leeks and scallions, should be eaten at least twice a week for the benefits that they offer.


Low-fat, vitamin D-fortified dairy products, especially those that contain live bacteria culture, can provide good amounts of calcium and vitamin D to further decrease risk.


Enjoy a handful of peanuts. Eating peanuts just 2 or more times each week was associated with a 58% lowered risk of colon cancer in women and a 27% lowered risk in men.


Alcohol intake should be greatly limited or, in people who are at high risk for rectal cancer, avoided completely.


Refined sugar and pickled foods should be removed from the diet.


In general, food consumption should not be excessive, but should provide just enough calories to support a healthy lifestyle that includes a moderate amount of exercise.