Diet and Cancer Risk
While the media often reports on foods that "prevent cancer" and we would love to be told that eating one particular food will prevent cancer, it is unlikely that such a food exists. It is more likely that a combination of good foods may have a preventive effect. Studies over the years have looked at our diets and what foods, if any, will lead to a lower risk of cancer. Fruits and vegetables, whole grains and unprocessed foods have all been promoted as reducing cancer risk. Unfortunately, studies have not consistently proven this to be true. Expert panels state that a diet high in fruits and vegetables "probably" reduces cancer risk, but we just don't know for sure.
However, a healthy diet plays an important role in a sort of "triangle" of cancer prevention. A healthy diet, combined with regular physical activity and maintaining a healthy weight has been shown to reduce cancer risk. This triangle is thought to be the second most important step, after not smoking, to preventing cancer. Diets high in some foods have been linked to a possible increased cancer risk and it is worth paying closer attention to their presence in your diet.
A diet that includes a high consumption of red meat (beef, pork and lamb) is thought to be a cause of colon and rectal cancers. Red meat has been thought to increase one's risk of developing other cancers, including breast, prostate, and stomach, but more recent research has not consistently found this to be true. There may be a link to an increase in pancreatic cancers, but studies have found mixed results. Red meat is not all bad, and eating some in moderation likely does not increase risk of cancer. The AICR recommends that people eat no more than 18 ounces (cooked weight) of red meats, including beef, pork and lamb, per week to reduce cancer risk.
Processed & Fermented or Cured Meats
Processed (hot dogs, bologna and lunchmeat) and cured or fermented meats (sausage, salami) eaten regularly increases the risk of colon, rectal, and gastric cancers. There may also be a link to endometrial and pancreatic cancers. These foods, as a result of how they are prepared, contain nitrosamines, nitrate and N-nitroso-compounds (NOCs), which have been shown to be carcinogens (cancer causing).
Salted and Pickled Foods
Foods preserved with salt, pickling or smoking are linked to increased rates of stomach (gastric) cancers. Salted foods such as meat and fish, and salt-preserved vegetables contain large amounts of salt, which appears to damage the lining of the stomach. Infection with H. Pylori bacteria also damages the stomach and the damage is worse in the presence of salt. This damage can lead to stomach cancer. People whose diets include regular pickled foods have been found to have higher rates of stomach cancer. This may be due to the presence of nitrates and high amounts of salt.
Compounds [Heterocyclic Amines (HCAs) and Polycyclic Aromatic Hydrocarbons (PAHs)] form as a result of cooking meats at high temperatures (pan frying or grilling). In high doses, these have been shown to cause cancer in animals. In turn, studies have found that eating lots of charred (or burned) meat may increase the risk of developing colon, rectal, pancreatic, and prostate cancers.
White Breads, Rice and Processed Grains
Eating white bread, white rice and processed grains may increase your risk for colon, rectal, and endometrial cancers because of their link to obesity. Try replacing these foods in your diet with whole grains and brown rice. Many studies have tried to link a diet high in whole grains to reduced cancer risk, but these have not always shown a benefit. The strongest link seen in these studies was that a diet high in fiber and whole grain foods may lower colon cancer risk.
Benefits of Vegetarianism
Studies have found that vegetarians and vegans have lower rates of heart disease, diabetes, high blood pressure and obesity. It is not clear if these benefits are strictly diet related, as vegetarians tend to lead healthier lifestyles overall (more exercise, not smoking) and it may be a combination of factors that leads to better health. A link between this diet and cancer risk has not been found. Though if a vegetarian diet is part of a healthy lifestyle, including exercise and a healthy weight, cancer risk is lowered.
Resources to learn more about how diet, physical activity and weight are related to cancer
The three components of the "cancer prevention triangle" are strongly inter-related and working to improve one can often lead to improvements in another. Use the links below to learn more about this prevention triangle and ways to work towards a healthier you.
- Eat Healthy and Get Active at the American Cancer Society website.
- Reduce Your Cancer Risk at the American Institute for Cancer Research.
- American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Prevention.
- WCRF/AICR Continuous Update Project.
- Dietary Guidelines for Americans, 2010 from the USDA.
- The US Department of Health & Human Services Physical Activity Guidelines for Americans.
- NIH AARP Diet & Health Study: a study developed at the National Cancer Institute of the National Institutes of Health to improve our understanding of the relationship between diet and health.
- The European Prospective Investigation into Cancer & Nutrition (EPIC): A large study by the International Agency for Research on Cancer investigating the relationships between diet, nutritional status, lifestyle and environmental factors and the incidence of cancer and other chronic diseases.
Appleby, P. N., & Key, T. J. (2016). The long-term health of vegetarians and vegans. Proceedings of the Nutrition Society,75(3), 287-293.
Chemicals in Meat Cooked at High Temperatures and Cancer Risk. National Cancer Institute (2015).
Johnson, I. T. (2016). The cancer risk related to meat and meat products. British medical bulletin, 121(1), 73-81.
Makarem, N., Nicholson, J. M., Bandera, E. V., McKeown, N. M., & Parekh, N. (2016). Consumption of whole grains and cereal fiber in relation to cancer risk: a systematic review of longitudinal studies. Nutrition reviews, 74(6), 353-373.
Penniecook-Sawyers, J. A., Jaceldo-Siegl, K., Fan, J., Beeson, L., Knutsen, S., Herring, P., & Fraser, G. E. (2016). Vegetarian dietary patterns and the risk of breast cancer in a low-risk population. British Journal of Nutrition, 115(10), 1790-1797.
Rohrmann, S., & Linseisen, J. (2016). Processed meat: the real villain?. Proceedings of the Nutrition Society, 75(3), 233-241.
Theodoratou, E., Timofeeva, M., Li, X., Meng, X., & Ioannidis, J. P. (2017). Nature, nurture, and cancer risks: genetic and nutritional contributions to cancer. Annual review of nutrition,37, 293-320.
WCRF/AICR Continuous Update Project Database and Findings. AICR.
Zhao, Z., Yin, Z., Pu, Z., & Zhao, Q. (2017). Association Between Consumption of Red and Processed Meat and Pancreatic Cancer Risk: A Systematic Review and Meta-analysis. Clinical Gastroenterology and Hepatology, 15(4), 486-493.