Nutrition And Cancer; Myth Or Fact

Image: Clare Bloomfield /

Image: Clare Bloomfield /

There is much confusion on what people should do to prevent and treat cancer. Some of those misguided information is given by health professionals themselves. Public belief about the role of nutrition in cancer range from the opinion that cancer is genetically determined to the other spectrum that a specific diet will prevent all cancer. These beliefs are myths to persuade consumers to make dangerous, inappropriate and ineffective dietary choices. Health professionals play an important role in minimising food faddism and dietary quackery with it’s false claims about diet and cancer. There is great need to determine the possible role of nutrients and dietary components in the development of neoplastic disease in human populations in order to develop rational and safe food and nutrition policies.


Below are some of the debunked misconceptions about nutrition and cancer:

Food additives and other harmful ‘chemicals’ are the major cause of cancer.

Small amounts of carcinogens have been blamed as the root of cancer. Some carcinogens exist naturally. For example, pyrrolizidine alkaloids exist in many plants. Some carcinogens are produced when foods are browned or burned. For example, nitrosamines generated from natural or added nitrites and amines, and possibly rancid fats. Other food carcinogens are caused by contamination like aflatoxin, which is one of several carcinogens transferred from molds to foods found in corn, grain, peanut butter, bread, cheese, fruit and apple juice.

The critical question is whether or not these chemicals are really hazardous to health if they are eaten in small amounts, with other food constituents which may be protective. To date, there is no evidence that these chemicals play a major role in cancer. One guideline to consider is from the American Institute for Cancer Research (AICR) about eating no more than 18 ounces of red meat per week. Following this standard might decrease the amount of carcinogen-containing meat you eat by default. In fact, some researchers suspect HCAs (Heterocyclic amines) and PAHs (Polycyclic Aromatic Hydrocarbons) may be partly responsible for increase colon-cancer risk.

Specific nutrients, such as vitamin E, vitamin C, vitamin A and selenium will prevent cancer.

We heard all the claims about the protective role of specific nutrients, from media to pharmacies. For vitamin C, few studies have adequately measured intake, but claims have been made based in differences in consumption of various types of fruits and vegetables. Same data have also been used to promote the protective effect of vitamin A. Even fewer data are available for vitamin E and selenium, because intakes are difficult to document.

However, an updated analysis, which was featured in the October 12 issue of JAMA, it was described that vitamin E supplementation can significantly increase the risk of prostate cancer. To date, the evidence is still small to suggest that these nutrients will prevent cancer.

Coffee increases risk of cancer

Recent evidence suggests that coffee might help prevent cancer and even contribute to longevity. Several new studies suggest that coffee helps prevent breast, prostate, head and neck cancers.

In one analysis by International Head and Neck cancer epidemiology consortium, it was found that people who drank about four or more cups a day had a 39% decreased risk of oral cavity and pharynx cancers combined.

In another study, Harvard University researchers presented data showing that men who drank the most coffee shows 60% decrease in lethal and advanced prostate cancers.

Results of a third study published in the January issue of the same journal showed a decreased risk of gliomas, or brain tumors, associated with coffee.

This link was found among those who drank five or more cups of coffee or tea a day. And yet a fourth study, in the April 2008 issue of Cancer Epidemiology, Biomarkers & Prevention, found that at least two or three cups of coffee a day can reduce the risk of breast cancer or delay it’s onset.

Epidemiological studies prove that some diets are better than others for preventing cancer.

Epidemiological studies give clues about the possible relationship between diet and cancer. Some research demonstrated that cancer mortality rates are correlated to types of foods and food patterns. Colon and breast cancer rates are generally high in countries consuming a ‘western’ diet, while stomach and esophageal rates are high in underdeveloped countries and those who have an ‘oriental’ diet. Sometimes results support the findings from the international studies; sometimes they do not.

However, the association between diet and cancer rate do not prove cause and effect. There are many other differences between countries than just the foods eaten. There are also many correlations between different foods in the diet. The apparent protective effect of fruits and vegetables might be due to vitamin C, vitamin A, fiber, folic acid or some other unidentified food constituent, or the fact that people who eat a lot of fruits and vegetables also eat more or less of other types of foods.

Red meat increases cancer

Consumption of red meat increases the risk of cancer, especially colorectal cancer. According to AICR, eating more than 18 ounces (510g) of red meat per week increases the risk of colorectal cancer. However, researchers do not yet know exactly how red meat effects the development of colorectal cancer. Red meat contains compounds that have been shown to damage the lining of the gut and possibly promote cancer. Cooking red meat at high temperatures can also produce other cancer-causing compounds. So, the best is to consume below 18 ounces (510g) of red meat a week. As a general rule, 18 ounces (510g) of cooked meat is roughly equivalent to 24 ounces (680g) of uncooked meat. There’s no need to eliminate red meat from the diet, but it makes sense to cut back.

Red meat in the category of processed meats should be avoided. Such meats include hot dogs, sausage, bologna and chemically treated jerkies (lean meat that has been trimmed of fat, cut into strips, and then been dried to prevent spoilage). Research shows that any amount of processed meat is linked to increased risk of colorectal cancer. There are many possible ways that processed meat may affect colorectal cancer. For example, compounds used as preservative may change into cancer-causing compounds in the body. Thus, processed meat should be avoided.

Antioxidant supplements help prevent cancer.

Antioxidant supplements, alone, do not help prevent cancer. However, antioxidants supplements, along with a healthy lifestyle, can help lower your chances of developing certain cancers.

The notion that antioxidant supplements, alone, do not help prevent cancer is supported by two studies published in The Journal of The American Medical Association. These studies concluded that vitamin A, C, E, and the mineral Selenium, which are active ingredients in most antioxidant supplements on the market today, have no effect on preventing cancers. Antioxidant supplements have been found to be most effective at helping improve the health and appearance of the skin.

Interestingly though, other studies have established the fact that individuals who consume a diet high in fruits and vegetables, which are the main dietary sources of vitamin A, C, E, and the mineral Selenium, on average, lives longer and are less likely to develop certain types of cancers, during their lifetimes.

In response to these two seemingly contradictory findings, scientists speculate that the combination of antioxidants, vitamins and other nutrients present in fruits and vegetables work together, in a combination that science cannot compress into a pill, to create the protective effect.

Polyunsaturated vegetable oils are healthy substitute.

Polyunsaturated fatty acid (PUFA) vegetable oils are a healthy substitute for animal fats. Many thought that PUFA oils are good for us and that saturated fats are hazardous and cause diseases including cancer. The fact is excess consumption of PUFA oils has been shown to contribute to a large number of disease conditions including increase risk of cancer. At the same time, saturated fats are a benefit to all these disease conditions. One reason the PUFA oils cause so many health problems is that they tend to become oxidized when subjected to heat, oxygen and moisture in cooking, extraction and processing. The oxidized oils contain high concentrations of ‘free radicals’ that are extremely reactive. PUFA are greatly immunosuppressive, and anything that suppresses the immune system is likely to cause cancer.

However, more research is needed to better understand which types of fat should be avoided and how much of each type alters cancer risk. Although monounsaturated and polyunsaturated fatty acids have been studied for a number of years, their effects are still unclear. More recent research on the effects of trans fatty acids also has yet to reach definitive conclusions.

The 2005 Dietary Guidelines for Americans recommend consuming less than 10 percent of calories from saturated fatty acids and keeping trans fatty acid consumption as low as possible for general health and the prevention of chronic disease, including cancer and heart disease. The Guidelines also recommend keeping total fat intake between 20 and 35 percent of calories, with most fats coming from sources of polyunsaturated and monounsaturated fatty acids, such as fish, nuts, and vegetable oils.


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