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Nutrition & Prostate Cancer

According to the American Institute for Cancer Research, approximately one third of all cancers are preventable through a combination of lifestyle habits – adequate physical activity, consumption of a healthy diet and maintaining a healthy body weight.

The strongest link between diet and the development of prostate cancer thus far appears to exist for the intake of dietary fat. The highest death rates from prostate cancer are found in industrialized countries where there is the highest per capita of fat consumption. In the Pacific Rim countries where the death rates from prostate cancer are the lowest, the lowest fat consumption is also found. It was been reported that men with the highest intake of red meat had an increased risk of developing prostate cancer about 2.65 greater than that of men who consumed the lowest amounts. Additionally, PSA levels reportedly were decreased in a study where men followed a vegan diet that included consumption of whole grains, beans, soy products, fruits, vegetables and 10% of total calories from fat. Subjects also exercised three hours per week and practiced stress-management techniques on a daily basis. Conversely, other studies have found no reductions in PSA levels in subjects following a low fat diet.

What the precise mechanism might be between fat intake and the risk for prostate cancer remains unclear and warrants further studies, however eating lower amounts of dietary fats, specifically red meat and fatty dairy products such as cheese, is recommended to reduce the risk for heart disease, the number one cause of death currently in the U.S. 

Micronutrients such as calcium, vitamins E and D, selenium, and zinc have been investigated as well regarding the risk for prostate cancer. Calcium intakes greater than 1500 mg/day have been associated with roughly double the risk for prostate cancer. Although this connection is not well understood, it has been postulated that a high calcium intake may result in lower blood levels of vitamin D. Lower vitamin D levels possibly cause the cells to lose their normal structure thereby increasing the ability of cells to proliferate – two causes of cancer.

An adequate calcium intake is associated with other health benefits such as reducing blood pressure, maintaining body weight and possibly reducing the risk for colon cancer. Therefore, men should strive for consuming adequate amounts (18-50.9 years of age: 1000 mg/d; >51 years of age: 1200 mg/d) and avoid an excessive intake (>1500 mg/d) unless advised otherwise.

Selenium intake has been shown to be associated with a lower incidence of prostate cancer in an initial report from the U of AZ in 1996. Other studies have reported a higher risk in men with low blood and toenail selenium levels. However, although selenium holds promise, further clinical studies are needed to determine if a true association exists. Currently the National Cancer Institute is testing whether selenium and vitamin E supplementation can prevent prostate cancer. Study results are expected around 2013.

Excessive consumption of zinc has been linked to an increased risk for prostate cancer as well as an increase risk of advanced prostate cancer in men consuming more than 100 mg/day from dietary supplements. The current recommendations are not to consume zinc from supplements in amounts > 15 mg/day. Supplementation with flaxseed oil supplements has also been associated with an increased risk for prostate cancer. Conversely, the intake of ground flaxseed has been associated with lower PSA levels in a small pilot study of men who were scheduled to have a repeat biopsy. This conflicting data is likely due to the fact that we don’t consume isolated nutrients but whole foods. The bottom line here is – men probably shouldn’t consume flaxseed oil supplements.

Lycopene has recently been touted as the magic bullet to prevent prostate cancer. Lycopene is a carotenoid that gives tomatoes, watermelon, pink grapefruit and guava their red color. Furthermore, lycopene is an antioxidant concentrated in the prostate gland. Researchers have found a reduced risk for prostate cancer in men over 65 years of age with the highest blood levels. Clinical studies have found a 20% reduced risk for prostate cancer when men consume meals with cooked tomatoes several times a week. Whether it’s specifically the lycopene or another health benefit yet to be identified in cooked tomatoes is unknown however. Although researchers don’t recommend that men should take lycopene supplements, consumption of a diet including meals with cooked tomato products twice a week is highly suggested.

In summary, to reduce the risk for prostate cancer as it relates to nutrition, men should limit their intake of dietary fat to 15-20% of total daily calories, consume a varied diet with a minimum of 5 servings of fruits and vegetables daily, consumed at least 2 meals/week containing cooked tomato products, consume a daily multi-vitamin supplement with not more than 15 mg/tablet of zinc. Additionally, daily physical activity and maintenance of a healthy body weight is associated with a reduced risk.