Many studies have tried to determine whether specific foods increase or decrease a person's risk of getting cancer. Unfortunately, different studies have had conflicting results, so it is hard to know what effect foods or dietary supplements have on cancer risk. A common problem is that when studies find that people who eat more of a certain food seem to have lower rates of a certain cancer, it can be difficult to tell whether those people also were different in terms of other risk factors (such as where they live, how much they smoke and drink, and so forth).
Often, when doctors do a controlled trial and randomly give some people a seemingly helpful food or supplement, the studies do not show a beneficial effect. Some foods and supplements have been studied more than others, and many studies are ongoing. The most convincing evidence is from studies that show diets low in fiber and high in processed meats increase cancer risk. Obesity, regardless of the type of diet, increases the risk of many cancers.
Alcohol
Alcohol increases the risk of cancers of the mouth, throat, esophagus, liver, breast, and the colon and rectum. People who smoke as well as drink have a much higher risk of these and other cancers.
Antioxidants
Antioxidants, such as vitamins C and E and beta-carotene (vitamin A
Artificial sweeteners
Although some early studies show an increased risk of bladder cancer, brain cancer, and lymphomas with certain sweeteners, these studies were done in animals. No studies in humans show a convincing increased risk of cancer with the use of these sweeteners.
Bioengineered foods (genetically modified [GMO] 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. There are no convincing data genetically modified foods increase cancer risk.
Calcium
Coffee
Although some older studies appeared to show a link between coffee consumption and cancer risk, more recent studies have not shown a benefit.
Fiber
Some studies report that a diet high in fiber reduces the risk of cancer, especially colorectal cancer, but these data are controversial.
Fish and omega-3 fatty acids
Some studies in animals suggest that omega-3 fatty acids may stop cancers from growing or slow their growth. However, these findings have not been replicated in humans.
Fluoride
Studies have not shown an increased risk of cancer in people who drink fluoridated water, use fluoride toothpastes, or undergo dental fluoride treatments.
Folate
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
Irradiated foods
Radiation of food, which is sometimes used to kill microorganisms in food, does not increase cancer risk.
Lycopene
Some studies suggest that lycopene, a natural red pigment and antioxidant found mainly in tomatoes, may reduce the risk of some cancers, but these data are controversial.
Meats cooked at high temperatures
Eating meat cooked at high temperatures, for example, by grilling or broiling, may introduce cancer-causing chemicals and increase cancer risk, especially colorectal cancer..
Organic food
There is no evidence that organically grown foods reduce cancer risk compared with conventionally-grown foods.
Pesticides
There is no evidence that pesticide residue found in small amounts on foods increases the risk of cancer.
Processed meats
People who eat large amounts of processed meats (for example, luncheon meats, hams, hot dogs) may be at risk for stomach, colon, and rectal cancers. Some evidence suggests that this is caused by nitrates found in the processed meats.
Saturated fats
Some studies have found higher rates of some types of cancer, such as breast cancer, in countries where fat intake is higher. However, no studies have found that decreasing fat intake decreases the risk of cancer. 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 and other health problems.
Selenium
There is no convincing evidence that selenium reduces cancer risk.
Spices
There is no convincing evidence that spices such as tumeric, capsaicin (red pepper), cumin, or curry decrease cancer risk.
Tea
Vitamin D
Vitamin D when taken with omega-3 fatty acid may decrease risk of death from cancer but does not decrease risk of developing cancer. Any potential benefit is greater in Blacks.
Vitamin E
There is no convincing evidence that vitamin E supplements decrease cancer risk, and some evidence suggests an increased risk of prostate and other cancers.
More information
The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
American Cancer Society: Stay Healthy: The American Cancer Society provides tips for people to make healthy choices and reduce the risk of cancer
National Cancer Institute: Cancer Causes and Prevention: The National Cancer Institute provides information on nutrients that may be associated with increases or decreases in the risk of cancer
U. S. Food and Drug Administration: Food Additives and GRAS Ingredients: Explains food additives including how they are approved and how they are used
