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Many studies have tried to determine whether eating specific foods increases or decreases a person's risk of getting cancer. Unfortunately, different studies sometimes have conflicting results, so it is hard to know what effect foods or dietary supplements have on cancer risk. Some foods and supplements have been studied more than others, and the American Cancer Society has tried to summarize what is currently known.
Antioxidants:
Antioxidants, such as vitamin C, vitamin E, and beta-carotene (vitamin A), are part of a well-balanced diet. However, whether taking supplements containing these antioxidants decreases the risk of cancer is not known. There is some evidence that taking high doses of beta-carotene supplements may increase the risk of certain types of cancer.
Bioengineered Foods:
Genes from different plants or from certain microorganisms are added to the genes of some plants to increase the plants' hardiness or resistance to pests or to improve them in some other way. No current evidence demonstrates that bioengineered foods have any effect on cancer risk.
Calcium:
High calcium intake, especially through calcium supplements, may increase the risk of prostate cancer.
Coffee:
Although some older studies appeared to show a link between coffee consumption and cancer risk, more recent studies have not shown any connection.
Saturated Fats:
Saturated fats may increase cancer risk. Of more importance, however, is that foods that contain high levels of saturated fats also contain many calories and may contribute to obesity, which is a risk factor for cancer.
Fiber:
There is little evidence that eating a diet that is high in fiber reduces cancer risk.
Fish and Omega-3 Fatty Acids:
Some studies in animals have shown that omega-3 fatty acids may slow cancer progression, but similar results have not been obtained in people.
Fluoride:
Studies have not shown an increased risk of cancer in people who drink fluoridated water or who use toothpastes or undergo dental fluoride treatments.
Folate:
Folate taken daily may decrease the risk of colon cancer.
Food Additives:
Food additives must be approved by the Food and Drug Administration before they are included in foods, so new additives undergo extensive testing. So far, no evidence shows that the levels of additives found in food products increase the risk of cancer.
Garlic:
Whether garlic is effective in reducing the risk of cancer is not yet known.
Irradiated Foods:
Radiation, which is sometimes used to kill microorganisms in food, does not appear to increase cancer risk.
Lycopene:
Some studies suggest that lycopene, which is found mainly in tomatoes, may reduce the risk of some cancers.
Processed Meats:
People who eat large amounts of processed meats may be at risk for stomach cancer. Some investigators attribute this finding to nitrates, which are in luncheon meats, hams, and hot dogs. This connection is unproved. Eating meats processed by salting or smoking may increase exposure to potential cancer-causing substances.
Meats Cooked at High Temperatures:
Eating meat cooked at high temperatures, for example by grilling or broiling, may increase cancer risk.
Organic Food:
Whether eating foods grown with organic methods reduces cancer risk is not yet known.
Pesticides:
There is no evidence that pesticide residue found in small amounts on foods increases the risk of cancer.
Saccharin:
Saccharin does not cause cancers in people.
Salt:
Diets containing large amounts of food that has been preserved by pickling or salting may increase the risk of stomach and throat cancer. No studies have found a similar risk for a small or moderate amount of salt for flavor.
Selenium:
Some studies suggest that selenium protects against some types of cancer.
Soy:
Studies do not yet show that soy supplements reduce cancer risk.
Tea:
Tea has not been shown to reduce cancer risk.
Vitamin D:
Vitamin D may have some benefit in reducing the risk of prostate cancer.
Last full review/revision August 2007 by Bruce A. Chabner, MD; Elizabeth Chabner Thompson, MD, MPH
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