ACS Guidelines on Nutrition and Physical Activity for Cancer Prevention

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Food additives, safety, and organic foods

The previous sections point to food choices that might lower a person's risk of cancer. Many people are also interested in other aspects of food intake and their potential impact on cancer risk.

Food additives and contaminants

Many substances are added to foods to prolong shelf and storage life and to enhance color, flavor, and texture. The possible role of food additives in cancer risk is an area of great public interest.

New food additives must be cleared by the US Food and Drug Administration (FDA) before being allowed into the food supply, and thorough testing is done in lab animals to determine any effects on cancer as part of this process. Additives are usually present in very small quantities in food, and some are nutrients that may have beneficial effects (for example, vitamins C and E are sometimes added to food products as a preservative).

Other compounds find their way into the food supply through agricultural use, animal farming, or food processing, even if their use is not directly intended for human consumption. Examples include growth hormones or antibiotics used in animal farming, small amounts of pesticides and herbicides in plant-based foods, and compounds such as bisphenol A (BPA) or phthalates that enter food from packaging. Some of these compounds are not known to directly cause cancer, but they may influence cancer risk in other ways – for example, by acting as hormone-like substances in the body.

Unintended contamination of food may also result in exposure to chemicals that are a cause of concern and may be related to cancer risk. Examples include heavy metals such as cadmium or mercury. These metals may enter the food supply if they build up the food chain, such as from fish, or they may enter through contamination or their natural presence in soil or water.

For many other compounds for which the effects on cancer risk are not clear, there may be other good reasons to limit exposure. But at the levels that these are found in the food supply, lowering cancer risk is unlikely to be a major reason to justify this.

Food processing

Food processing may also alter foods in ways that might affect cancer risk. An example is the refining of grains, which greatly lowers the amount of fiber and other compounds that may reduce cancer risk.

The processing of meat, by adding preservatives such as salt or sodium nitrite to prevent the growth of germs, or smoking the meat to preserve or enhance color and flavor, may add compounds that might increase the potential of these foods to cause cancer. Studies have linked eating large amounts of processed meats with an increased risk of colorectal cancer. This may be due to nitrites, which are added to many lunch meats, hams, hot dogs, and other processed meats.

Some food processing, such as freezing and canning vegetables and fruits, can preserve vitamins and other components that may decrease cancer risk. Cooking or heat-treating (such as when canning) vegetables breaks down the plant cell walls and may allow the helpful compounds in these foods to be more easily digested. But some of these methods may also lower the content of some heat-sensitive vitamins, such as vitamin C and some B vitamins.

Irradiated foods

Irradiation of food products is one way to limit the risk of germ contamination and food poisoning. In the United States, some foods, such as spices, are routinely irradiated. Irradiated meats and other foods are also widely available. Because radiation is known to cause cancer, there has been concern that food irradiation may present a cancer risk. However, radiation does not remain in foods that have been irradiated.

Organic foods

Concern about the possible effects of food additives on health, including cancer, is one reason that many people are now interested in organic foods. Organic foods are often promoted as an alternative to foods grown with conventional methods that use chemical pesticides and herbicides, hormones, or antibiotics. These compounds cannot be used for foods labeled as "organic." Organic foods, as defined by the US Department of Agriculture (USDA), also exclude genetically modified foods or foods that have been irradiated.

Whether organic foods carry a lower risk of cancer because they are less likely to be contaminated by compounds that might cause cancer is largely unknown.

Several studies have looked at the nutrient content of organic versus conventionally grown fruits or vegetables, and while some studies suggest a higher nutrient content, others suggest no difference. It is not known if the nutritional differences that have been reported would result in health benefits such as a reduced cancer risk.

Vegetables, fruits, and whole grains should form the central part of a person's diet, regardless of whether they are grown conventionally or organically.


Last Medical Review: 01/11/2012
Last Revised: 01/11/2012