During the last decade, hundreds of studies have investigated the association between diet and prostate health. The good news for your older male customers is much of the research shows a strong link between eating well and a reduced risk of cancer and other prostate conditions.
The prostate is a walnut-sized gland below the bladder that secretes fluids to help transport sperm. Prostate cancer is the second leading cause of male cancer deaths in the United States, according to the National Cancer Institute, and generally affects men over age 60. Older men are also susceptible to benign prostatic hyperplasia, a painful enlargement of the gland that may obstruct urine flow or block it completely; and prostatitis, an inflammation of the prostate caused by bacterial, fungal or viral infections.
Foods With Influence
Studies have determined that the following foods and nutrients are associated with prostate health. Much of the supporting research is epidemiological, or population-based, and makes associations between men's diets and their health risks. As studies go, such research can be susceptible to interpretive error, but it forms an important basis for later, better-controlled studies.
Cruciferous vegetables: These include cabbage, brussels sprouts, broccoli, bok choy and cauliflower. Researchers think three separate compounds in the brassica family—indole-3-carbinol, sulforaphane and glucaric acid—help eliminate cancer-causing substances such as hormones and environmental toxins before they damage cells. A controlled population study by researchers at the Fred Hutchinson Cancer Research Center in Seattle found men who ate three or more servings of cruciferous vegetables per week decreased their risk of prostate cancer by 41 percent compared with those who ate fewer than one serving (Journal of the National Cancer Institute, 2000). How cruciferous vegetables are prepared affects their chemical constituents. Instead of boiling broccoli and other crucifers, researchers recommend lightly steaming or microwaving the vegetables to retain their cancer-fighting nutrients.
Red meat: A high-fat diet is one of the strongest risk factors for developing cancer, especially prostate cancer. The saturated fats found mostly in red meats, such as beef, but also in some dairy and processed foods, step up the body's production of free radicals, which in turn harm healthy cells and increase DNA damage. High-fat diets also increase production of testosterone, which in large enough amounts can trigger prostate tumor growth. Studies tracking the health and diets of Asians and Africans who relocate to Western countries find their switch from traditional low-fat foods to diets high in saturated fats is consistently associated with a marked increase in their cancer rates.
A study conducted by Harvard Medical School researchers correlated the fat intake of 51,529 men ages 40 to 75 with the group's incidence of advanced prostate cancer. Researchers found that eating animal fat, especially from beef, was directly associated with prostate cancer risk. Fats from fish and dairy products other than butter carried no risk (Journal of the National Cancer Institute, 1993). It's suspected carcinogens formed while cooking animal fats at high temperatures may also contribute to prostate cancer. In addition, meats are high in alpha linolenic acid, a fatty acid that some studies correlate with increased cancer risk.
Selenium: Many studies suggest the mineral antioxidant selenium has a variety of anti-cancer properties. Selenium works with vitamin E to protect cells from free radical damage, and low selenium blood levels are reported in people with cancer. Good food sources of selenium include organ meats, fish and shellfish, as well as whole grains and cereals such as barley and bulgur.
The selenium content of grains is greatly affected by growing conditions and processing techniques. So brown rice, for instance, contains higher amounts of selenium than highly processed white rice.
Soy: Although often recommended for women's health, it seems a soy-rich diet may also help prevent prostate cancer. Isoflavones in soy such as genistein and daidzein weakly mimic the estrogen men and women naturally produce. The upshot for men is that these isoflavones may reduce the harmful effects of testosterone, which is associated with cancerous prostate cell growth. Laboratory studies also suggest genistein inhibits and helps kill prostate cancer cells. Soybeans and many soy foods, including tofu, soymilk and some soy protein powders, all contain beneficial isoflavones. In fact, a study evaluating the relationship between soymilk and prostate cancer incidence among 12,395 California men demonstrated that drinking soymilk more than once a day was associated with a 70 percent reduction in prostate cancer risk (Cancer Causes Control, 1998). A few studies show that soy isoflavones may also help prevent BPH.
Tomatoes: Lycopene, the carotenoid that makes tomatoes red, appears to provide strong protection against prostate cancer. The first study to document the link between lycopene and prostate health was conducted by Harvard Medical School researchers who surveyed nearly 48,000 men about their diets and assessed their prostate cancer risk. They found that men who ate 10 or more servings (one-half cup) of tomato-based foods each week had a 35 percent lower risk of developing prostate cancer than those who ate only 1.5 servings (Journal of the National Cancer Institute, 1995). More recent research confirms this association. Although lycopene is also found in watermelon and guava, tomatoes are the richest source. Lycopene from cooked tomato products is better absorbed by the body than the lycopene in raw tomatoes.
Zinc: The prostate contains about 10 times more zinc than any other body tissue. Because men with prostate cancer are reported to have low zinc levels, some researchers suspect the mineral is essential to prostate function and may even help prevent cancer. One laboratory study suggests zinc interferes with prostate cancer cell growth by triggering cell death (Prostate, 1999). Although no studies have examined the role of dietary zinc in prostate health, some practitioners believe it is helpful in treating BPH and chronic prostatitis. Pumpkin seeds, oysters, lean meats and wheat germ are all high in zinc.
As the association between diet and prostate health grows stronger, studies will begin narrowing the food focus. The next step in understanding food's cancer-fighting properties may involve putting older men on strict, high-soy diets rather than relying on diet surveys, or comparing selenium supplements to placebos. When this happens, staples such as broccoli and barley will become such commonsense preventive steps, they may just sell themselves.
Catherine Monahan has published more than 150 articles on health, medicine and nutrition. She can be reached at [email protected].
Natural Foods Merchandiser volume XXIV/number 2/p. 32, 34