The link between meat consumption and prostate cancer risk is one that has been studied for decades. The research spans the impact of saturated fat, hormones, nitrates and nitrites, and other potentially harmful substances in meat, as well as the effects of various cooking methods on the risk of prostate cancer development. In 1997, for example, the American Institute for Cancer Research (AICR) published a review of the major studies on food, nutrition, and the prevention of cancer. The experts determined that consumption of beef, lamb, and pork possibly increased the risk of cancer of the prostate, breast, kidney, and pancreas. (AICR 1997)
One of the studies in the review was a case-control study conducted at Harvard University, in which nearly 15,000 male physicians who were part of the Physicians’ Health Study were evaluated. The investigators found that men who consumed red meat at least five times a week had a relative risk of 2.5 for developing prostate cancer when compared with men who ate red meat less than once a week. (Gann 1994)
Another study included in the review was the Harvard Health Professionals Follow-Up Study, which reported on the food consumption habits of nearly 52,000 health professionals. The report, based on 3 to 4 years of follow-up data, noted a statistically significant relationship between a greater intake of red meat and the risk of advanced prostate cancer. (Giovannucci 1993)
In a subsequent study conducted by the National Cancer Institute of more than 175,000 men spanning 1995 to 2003, the researchers evaluated the meat consumption of the participants, including the type of meat consumed and how it was cooked. By 2003, 10,313 men had developed prostate cancer, and 419 of these had died. (Sinha 2009) The authors evaluated the meat consumption of all the participants and found that after they adjusted for factors known to increase the risk of prostate cancer, they discovered that “men who ate the most red meat were 12 percent more likely to develop prostate cancer and 33 percent more likely to have advanced cancer than those who ate the least amount of red meat”.
Although the evidence linking the consumption of red meat and prostate cancer is strong, there are some who say such a relationship does not exist. In a study published in Nutrition Journal, researchers conducted a meta-analysis of prospective studies, selecting 15 concerning red meat and 11 that included processed meat from a pool of 143. Overall, an analysis of meat intake and amount consumed showed no association between high versus low consumption of red meat or each 100 grams of red meat consumed and prostate cancer. The authors also reported there was no association between red meat consumption and advanced prostate cancer. However, when some of the studies were evaluated individually, several showed a slightly elevated or marginally significant risk of prostate cancer, metastatic prostate cancer, or advanced prostate cancer associated with eating red meat, processed meat, or both. The study was partially funded by the Cattlemen’s Beef Board through the National Cattlemen’s Beef Association. (Alexander 2010)
The National Cancer Institute study also found that processed meats are associated with a higher risk of prostate cancer. When the authors compared red processed meats (e.g., bacon, bologna) with white varieties (e.g., processed turkey slices) the red meats were linked to a greater cancer risk than the white meats. Processed and cured meats also contain nitrates, which are preservatives added to meats such as cold cuts and bacon. These preservatives are associated with an increased risk of prostate cancer.(Sinha 2009)
Cooking Methods and Prostate Cancer
When meat (especially red) is cooked at very high temperatures, compounds called heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) are formed. These compounds have been linked to various cancers in humans. A Vanderbilt University study in the journal Nutrition and Cancer evaluated the relationship between consumption of well-done meat and meat carcinogen exposure with the risk of cancer. (Zheng 2009) The results from this study show that high intake of well-done meat and high exposure to carcinogens in meat, especially HCAs, may increase the risk of cancer, including prostate cancer.
Results of a study conducted by researchers at the Johns Hopkins Kimmel Cancer Center found that grilling, broiling, and searing meats were all equally risky when it comes to prostate cancer. In the study, the investigators studied a chemical called PhIP, which is formed when muscle meats (e.g., beef, chicken, fish, pork) are cooked at very high temperatures. The process sets off a chemical reaction between protein and a chemical in the meat, and the combination forms a new substance that may be a carcinogen. The researchers discovered that rats fed PhIP developed precancerous lesions of the prostate. After eight weeks of being fed PhIP in their meals, the cells began to proliferate, indicating that PhIP both initiates and promotes cancer cells. The findings were presented at the 2006 annual meeting of the American Association for Cancer Research.
In a subsequent study from Imperial College London, scientists noted that PhIP can activate estrogen receptor-mediated pathways at doses that are similar to those found in the body after people eat a meal of cooked meat. The authors reported that their findings provide strong support that PhIP initiates and promotes tumors and that dietary exposure to PhIP could contribute to the development of cancer in humans. (Creton 2007)
The National Cancer Institute study also examined the associations between meat consumption, iron, nitrite/nitrate, and prostate cancer in a group of 175,343 men aged 50 to 71 years. (Sinha 2009) During a nine-year follow-up period, the researchers identified 10,313 cases of prostate cancer and 419 deaths from prostate cancer. When they evaluated the consumption of red and processed meat, the researchers found that iron, barbecued and grilled meat were all associated with total and advanced prostate cancer, while nitrites and nitrates were associated with advanced prostate cancer.
Fat and Prostate Cancer
A high-fat diet raises levels of estrogen in the body, and fat cells harbor estrogen. Therefore men who have a high intake of fat, which is abundant in meat and other animal products, risk raising their estrogen levels and thus the possibility of prostate cancer. In the December 2010 issue of Nutrition and Cancer, the authors evaluated data regarding intake of red meat, fat, garlic, and tomato/tomato products, along with demographic and medical information, for 194 men who had prostate cancer and 317 healthy controls. They found a significant trend of increasing risk of prostate cancer associated eith intake of dietary fat, as well as an increased risk with dietary red meat, along with a protective effect from tomatoes and garlic. (Salem 2010)
Hormones, Meat, and Prostate Cancer
About two-thirds of the cattle raised in the United States are given hormones, including testosterone and estrogen, because it increases both their growth and meat yield. Sheep are the only other food animals that are allowed to be given hormones in the United States. These hormones are then passed along to individuals who consume these products. Hormone residues in food may promote the development of prostate cancer in men. Yet neither the Food and Drug Administration nor the US Department of Agriculture monitor meat in the United States for sex hormone levels. (Weil)
Support for the role of estrogen in prostate cancer comes from a report in Medical Hypotheses, in which the authors commented on epidemiological studies that suggest milk consumption is likely a risk factor for prostate cancer, and that it is the estrogen in milk that is the possible contributor. They noted that a diet of milk/dairy products and meat is related to increasing levels of estrogens, and that estrogen levels in prostate fluid correlate very well with prostate cancer. In addition, they pointed out that both estrogen and testosterone have also been used to induce prostate cancer in rodent models as well. (Qin 2004)
Another hormone found in meat and dairy products may also increase the risk of prostate cancer: insulin-like growth factor (IGF-1). A University of Oxford team conducted a review of 12 studies that included nearly 9,000 men. They discovered that men who had high blood levels of IGF-1 were up to 40 percent more likely to develop prostate cancer than men who had low levels of the hormone. (Roddam 2008)
Alternatives to a Meat-Based Diet
Men can help reduce their risk of prostate cancer by following a diet that limits or eliminates meat and focusing on high-fiber, low-fat, nutrient-rich sources of protein. Unlike a diet that focuses on meat and poultry, which are high in saturated fat and cholesterol and low in or lacking fiber, vitamins and minerals, and healthy fats (e.g., omega-3s, monounsaturated), a diversified plant-based diet can provide all the protein and other essential macronutrients, vitamins, minerals, and fiber to support and maintain health and help prevent prostate cancer. Plant foods that provide good to excellent amounts of protein include dried beans (e.g., black, kidney, pinto, red), lentils, split peas, fermented soy, amaranth, quinoa, kamut, buckwheat, and others. These foods also provide high amounts of fiber, which can help eliminate cancer-causing toxins from the body.
AICR: World Cancer Research Fund. Food, nutrition, and the prevention of cancer: A global perspective. American Institute of Cancer Research. Washington, DC: 1997.
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Qin LQ et al. Estrogen: one of the risk factors in milk for prostate cancer. Med Hypotheses 2004; 62(10: 133-42
Roddam AW et al. Insulin-like growth factors, their binding proteins, and prostate cancer risk: analysis of individual patient data from 12 prospective studies. Ann Intern Med 2008 Oct 7; 149(7):461-71, W83-8
Salem S et al. Major dietary factors and prostate cancer risk: a prospective multicenter case-control study. Nutr Cancer 2010 Dec 15:1
Sinha R et al. Meat and meat-related compounds and risk of prostate cancer in a large prospective cohort study in the United States. Am J Epidemiol 2009 Nov 1; 179(9): 1165-77.