Prevent colon cancer article.
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 and is the third most common form of cancer in the United States and the third most common cause of cancer death. Colon cancer develops when cells of the colon are exposed to chemicals or carcinogens that cause damage to their DNA. This damage leads to mutations in the cells, which may then reproduce out of control and spread to other parts of the body, leading to organ damage and eventually death.
There is a great variance worldwide in the incidence of colorectal cancer with some countries having 10 to 20 times the rate of other countries. Although genetics may play a role in the disease, many researchers believe that as much as 90% of these differences can be explained by dietary factors alone. Fortunately, there are many dietary habits and nutrients that may help to prevent this devastating and potentially deadly disease.
Organically grown fruits and vegetables
Extra virgin olive oil
Whole grains for their high fiber
Cold water fish such as salmon, tuna, herring, mackerel and halibut for their beneficial omega 3 fatty acids
Onions, garlic and leeks
Brassica vegetables including broccoli, kale, mustard greens (June 3, 2004)
Ginger (December 8, 2003)
Soy foods (June 28,2004)
Grapefruit (October 19, 2004)
Avoid red meats, omega 6 fatty acids, saturated fats, refined Sugar and alcohol.
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 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.
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.
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 those things that can increase risk. 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.
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.
Nutrients That May Reduce Risk of Colorectal Cancer
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)
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.(October 24, 2003)
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.
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 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 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 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 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.
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.
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.(December 31, 2003)
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 the July 2003 issue of Free Radical Biology 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). (September 8, 2003)
A review of 91 studies on the relationship between diet and cancer published in the October 2004 issue of the International Journal of Cancer 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. (October 21, 2004)
Food sources of omega-3 fatty acids include flax seeds and walnuts as well as cold water fish, like salmon, cod, tuna, and halibut.
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
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.
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:
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.(June 3, 2004)
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.
“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.
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. (June 28, 2004)
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.
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. (October 19, 2004)
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.
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. (October 24, 2003)
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.
Turmeric is a seasoning rich in a substance 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.
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.). (December 8, 2003)
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.
Substances to Avoid
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.
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 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.
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.
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.
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.
Alcohol intake should be greatly limited or, in people who are at high risk for rectal cancer, avoided completely.
Refined sugar 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.
The Condition Specific Meal Planner for Colorectal Cancer has menus that cover the nutritional needs of this condition over a four day period.
Ames, BN. Micronutrient deficiencies. A major cause of DNA damage. Ann N Y Acad Sci 1999;889:152-6.
Bancroft LK, Lupton JR, Davidson LA, Taddeo SS, Murphy ME, Carroll RJ, Chapkin RS. Dietary fish oil reduces oxidative DNA damage in rat colonocytes. Free Radic Biol Med Jul 15;35(2):149-59.
Bartsch H, Nair J, Owen RW. Dietary polyunsaturated fatty acids and cancers of the breast and colorectum: emerging evidence for their role as risk modifiers. Ann N Y Acad Sci 1999;889:87-106.
Biasco G, Paganelli GM. European trials on dietary supplementation for cancer prevention. Oncology (Huntingt) 1999;13:89-97; discussion 97-100, 105.
Bode A. Ginger is an effective inhibitor of HCT116 human colorectal carcinoma in vivo. paper presented at the Frontiers in Cancer Prevention Research Conference, Phoenix, AZ, Ocbober 26-3-, 2003.
Eastwood, GL. Pharmacologic prevention of colonic neoplasms. Effects of calcium, vitamins, omega fatty acids, and nonsteroidal anti-inflammatory drugs. Cancer Causes Control 1997;8:786-802.
Erhardt JG, Meisner C, Bode JC, Bode C. Lycopene, beta-carotene, and colorectal adenomas. Am J Clin Nutr. 2003 Dec;78(6):1219-24.
Garay CA, Engstrom PF. Chemoprevention of colorectal cancer: dietary and pharmacologic approaches. J Natl Cancer Inst 1997;89:1006-14.
Giovannucci E, Willett WC. Dietary factors and risk of colon cancer. Dig Dis 1996;14:119-28.
Guo JY, Li X, Browning JD Jr, Rottinghaus GE, Lubahn DB, Constantinou A, Bennink M, MacDonald RS. Dietary soy isoflavones and estrone protect ovariectomized ERalphaKO and wild-type mice from carcinogen-induced colon cancer. J Nutr. 2004 Jan;134(1):179-82. .
Higginbotham S, Zhang ZF, Lee IM, Cook NR, Giovannucci E, Buring JE, Liu S. Dietary glycemic load and risk of colorectal cancer in the Women's Health Study. J Natl Cancer Inst. 2004 Feb 4;96(3):229-33.
Le Bon, AM, Siess, MH. Organosulfur compounds from Allium and the chemoprevention of cancer. Cancer Causes Control 1996;7:127-46.
Lieberman D, Prindiville S, Weiss D, Willett W. Risk factors for advanced colonic neoplasia and hyperplastic polyps in asymptomatic individuals. JAMA. 2003;290:2959-2967.
Lipkin M, Reddy B, et al. Dietary factors in human colorectal cancer. Ann Med 1994;26:443-52.
Lupton, JR, Turner, ND. Potential protective mechanisms of wheat bran fiber. Am J Clin Nutr 1994;59:1162S-5S.
Ma J, Giovannucci E, Pollak M, Leavitt A, Tao Y, Gaziano JM, Stampfer MJ. A prospective study of plasma C-peptide and colorectal cancer risk in men. J Natl Cancer Inst 2004 Apr 7;96(7):546-53. .
Patterson RE, White E, et al. Vitamin supplements and cancer risk: the epidemiologic evidence. Drug Metabol Drug Interact 2000;17:51-79.
Peters HP, De Vries WR, et al. Potential benefits and hazards of physical activity and exercise on the gastrointestinal tract. Gut 2001;48:435-9.
Pierre F, Tache S, Petit CR, Van Der Meer R, Corpet DE. Meat and cancer: haemoglobin and haemin in a low calcium diet promote colorectal carcinogenesis at the aberrant crypt stage in rats. Carcinogenesis. Aug 1 [Epub ahead of print].
Potter, JD. Nutrition and colorectal cancer. Carcinogenesis 1999;20:2209-18.
Reddy B. Omega-3 fatty acids in colorectal cancer prevention. International Journal of Cancer Oct 2004, 112(1):1-7.
Stone, WL, Papas, AM. Tocopherols and the etiology of colon cancer. Annu Rev Nutr 1999;19:545-86.
Suzuki, Kohno H, Sugie S, Murkami A, Yano M, Ohigashi H, Tanaka T. Citrus nobiletin inhibits azoxymethane-inducved rat colon carcinogenecis. The 228th ACS National Meeting, Philadelphia, PA, August 24, 2004.
Symolon H, Schmelz EM, Dillehay DL, Merrill AH Jr. Dietary soy sphingolipids suppress tumorigenesis and gene expression in 1,2-dimethylhydrazine-treated CF1 mice and ApcMin/+ mice. J Nutr. 2004 May;134(5):1157-61.
Terry P, Jain M, Miller AB et al. Dietary intake of folic acid and colorectal cancer risk in a cohort of women. Int J Cancer 2002 Feb 20;97(6):864-7.
Turner, Vanamala J, Leonardi T, Patil B, Murphy M, Wang N, Pike L, et al. Grapefruit and its isolated bioactive compounds act as colon cancer chemoprotectants in rats. The 228th ACS National Meeting, Philadelphia, PA, August 24, 2004.
Verhoeven DT, Goldbohm RA, et al. Epidemiological studies on brassica vegetables and cancer risk. Am J Med 1999;106:24S-7S.
Walters DG, Young PJ, Agus C, Knize MG, Boobis AR, Gooderham NJ, Lake BG. Cruciferous vegetable consumption alters the metabolism of the dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in humans. Carcinogenesis. 2004 Apr 8 [Epub ahead of print].
Willett WC. Micronutrients and cancer risk. Cancer Epidemiol Biomarkers Prev 1996;5:733-48.
Wollowski I, Rechkemmer G, Pool-Zobel BL. Protective role of probiotics and prebiotics in colon cancer. Am J Clin Nutr 2001;73:451S-5S.
Wu K, Willet WC, Fuchs CS et al. Calcium intake and risk of colon cancer in women and men. J Natl Cancer Inst 2002 Mar 20;94(6):437-46.