Meat in Relation to Cancer
Epidemiological studies have proven a relationship between red meat consumption and colorectal cancer, and suggested a link with esophageal, lung, pancreas, and endometrial cancers. Harvard studies found that daily meat eaters have approximately three times the colon cancer risk, compared to those who rarely eat meat. Large studies in England and Germany showed that vegetarians were about 40% less likely to develop cancer. It is recommended that people limit their intake of red meat.
Some research suggests that the form of iron in red meat, heme iron, may increase cell proliferation in the intestinal mucosa. Nitrosation of meat may increase the toxicity of heme in cured-meat products. It is believed that excess exposure to iron leads to the excess generation of free radicals, oxidative stress, inflammation, and hypoxia.
Some experts believe that the fat content of meat explains some of the link to cancer. Studies show that high-fat diets, in general, may lead to carcinogenesis via insulin resistance or increased fecal bile acids. The liver makes bile, which is stored in the gallbladder, to absorb fat. This bile goes to the intestine after eating. In the intestine, the bile acids modify the fat, so that the body can absorb it. Some experts believe that bacteria in the intestine turn these bile acids into “secondary bile acids,” which are carcinogenic, explaining why high-fat diets seem to have a link to increased cancer risk. Fat consumption also increases hormone production, thus increasing the risk of hormone-related cancers, such as breast and prostate cancer.
The epidemiologic studies published to date conclude that the risk for individuals in the highest category of processed meat-eaters (excessive intake) is between 20% and 50%, compared with nonmeat-eaters. Hypotheses for this link include the formation of N-nitroso compounds in the gut after eating red meat or processed meat. Sodium nitrite is used to prevent the growth of Clostridium botulinum, and sodium nitrate is used as a color fixative in cured meat and poultry. Nitrites combine with amines during the cooking process, and this forms N-nitroso compounds, which are carcinogenic.
Processed meat is linked to cancers of the mouth, urinary bladder, lung, prostate, esophagus, stomach, and brain. It is recommended that people limit their consumption of processed meat.
Another possible factor is the production of mutagens formed during grilling or smoking of meat. Cooking meat at high temperatures leads to the production of carcinogenic heterocyclic amines and polycyclic aromatic hydrocarbons. In some studies, grilled chicken has formed higher concentrations of these heterocyclic amines than other types of cooked meat. Marinating meat and precooking it in the microwave before grilling or smoking may help to reduce the formation of these mutagens.
Butylated hydroxyanisole (BHA)
BHA is a petroleum-derived food additive that reduces the rate at which food spoils. It was first used as an antioxidant in 1947 and is now used in a wide range of foods, including in meats to prevent the fat from going rancid. It is sometimes used in conjunction with a related antioxidant, butylated hydroxytoluene (BHT). According to the National Toxicology Program, funded by the US Dept of Health and Human Services, BHA is “reasonably anticipated to be a human carcinogen.” When administered in the diet, BHA induced papillomas and squamous cell carcinomas in the forestomach in rats of both sexes and male Syrian golden hamsters.
Tips for reducing your risk of cancer
- Focus on poultry, fish, beans, legumes, and meat replacement products
- Prepare red meat by baking, roasting, broiling, or poaching it, if you are going to it
- Marinate red meat before grilling it or cook it in the microwave for 2 minutes
- Flip your meat faster when grilling—about every 6 minutes
- Choose leaner cuts of meat
- Microwave meat for 2 minutes before grilling it
References and recommended readings
Kushi LH, Doyle C, McCullough M, et al; American Cancer Society 2010 Nutrition and Physical Activity Guidelines Advisory Committee. American Cancer Society guidelines on nutrition and physical activity for cancer prevention: reducing the risk of cancer with healthy food choices and physical activity. CA Cancer J Clin [serial online]. 2012;62:30-67. Available at: http://onlinelibrary.wiley.com/doi/10.3322/caac.20140/full. Accessed April 6, 2012.
Liebman B. The real cost of red meat. Nutrition Action Healthletter (Center for Science in the Public Interest). June 2009;3-7.
Pittman G. Too much red meat linked with higher kidney cancer risk: study. Available at: http://www.huffingtonpost.com/2011/12/29/red-meat-kidney-cancer_n_1173417.html. Accessed March 3, 2012.
The Cancer Project. Cancer prevention and survival: cancer facts—meat consumption and cancer risk. Available at: http://www.cancerproject.org/survival/cancer_facts/meat.php. Accessed April 6, 2012.
Review Date 4/12