Fat . Although there is consistency found among the epidemiologic findings implicating dietary fat from animal sources and prostate cancer, a direct cause and effect relationship is difficult to establish. According to one theory, fat increases the production of testosterone, which in turn stimulates the growth of prostate cancer cells. It's still uncertain, however, whether the possible relationship between a high-fat diet and the development of cancer is due to the total amount of fat in your diet or to a specific type of fat, such as saturated fat. It's also difficult to distinguish between the effect of fat and the effect of total calories.

Legumes and yellow-orange and cruciferous vegetables . A study evaluated 1,619 prostate cancer cases and 1,618 controls in a multicenter, multiethnic population found that intake of legumes and yellow-orange and cruciferous vegetables was associated with a lower risk of prostate cancer.

Tomatoes and other lycopene-rich food. Eating tomato products or other lycopene-rich foods, may lower risk of prostate cancer. Lycopene is an antioxidant that gives vegetables and fruits their red color. However, studies involving lycopene supplements did not provide the same benefits as lycopene derived from whole foods.

Soy and Soy products — such as soy milk, soy flour, soy nuts, tofu and tempeh — contain isoflavones, plant-based compounds that may reduce risk of prostate cancer. Many beneficial effects have been attributed to the isoflavones genistein and daidzein. Experiments in laboratory have shown that genistein has a broad variety of actions including inhibiting the growth of androgen-dependent and independent cell lines. Genistein is a potent modulator of various tyrosine kinase receptors such as epidermal growth factor, insulin, insulin growth factor-1, and platelet-derived growth factor. The strength for its recommendation came mainly from epidemiologic studies.

Garlic. Garlic appears to reduce the risk of many types of cancer, including prostate cancer. It's thought that sulfur compounds in garlic enhance immune function, which helps combat tumor growth. These compounds may also slow the spread of cancer cells and increase the production of enzymes that help eliminate cancer-causing substances. Large-scale studies involving human subjetcs have not confirmed this theory.

Green tea. Green tea contains a natural substance called epigallocatechin gallate (EGCG). This compound appears to inhibit enzyme activity necessary for cancer growth, but large-scale studies involving human subjects have not evaluated this theory.

Vitamin E . Vitamin E is a potent antioxidant that has the ability to inhibit malignant transformation. This fat-soluble vitamin has a potent effect on the immune system. The most biologically active and common source of vitamin E is alpha-tocopherol, one of 8 naturally occurring forms. This vitamin has been shown to have a substantial protective effect against prostate cancer. Heininen et al reported a 32% decrease in the incidence of prostate cancer in men receiving 50 mg of alpha-tocopherol daily. This reduction was noted for clinical cancer but not for latent cancer. Mortality from prostate cancer was reduced by 41% in the alpha-tocopherol group, but there was no apparent effect on the time interval between diagnosis and death.

Selenium. Selenium is an essential trace nutrient that is critical for the activity of glutathione peroxidase, which protects DNA and other cellular molecules against oxidative damage. The basis for a trial of selenium as a chemopreventive agent in prostate cancer dates back to a study reported in 1996 involving 1,000 men and women who were taking selenium 200mcg daily to prevent skin cancer. Although no benefit was found in preventing skin cancer, more than 60% fewer new cases of prostate cancer were reported in men taking selenium daily as compared with those who did not receive the element. Another study that investigated the association between the risk of prostate cancer and selenium levels showed higher selenium levels were associated with a significantly reduced risk of developing advanced prostate cancer (odds ratio = 0.49 with selenium compared to a risk ratio of 1.0 for those with low selenium levels).

Because preliminary data suggest that both selenium and vitamin E may reduce the risk of prostate cancer, a large randomized, prospective, double-blind study has been designed to determine whether selenium and vitamin E can reduce the risk of prostate cancer among healthy men. Enrollment for the Selenium and Vitamin E Cancer Prevention Trial (SELECT) began in 2001 and will include 32,000 men. The study agents will be taken orally for a minimum of seven and a maximum of 12 years with assessments of general health, incident prostate cancer, and toxicity performed at 12-month intervals.

Vitamin D. Vitamin D is involved in calcium metabolism and in the control of cell growth and apoptosis. Dietary vitamin D can be ingested from plant sterols (ergosterol), milk, and foods supplemented with this vitamin. It also is produced by the action of ultraviolet radiation on the skin. Animal experiments have demonstrated that vitamin D (1,25-dihydroxyvitamin D3) inhibits the growth and invasiveness of prostate cancer cells. Large scale study involving human subjects have not evaluated this theory.