990314 Animal Fat May Raise Prostate Cancer Risk

New York - A high intake of animal fat appears to increase the risk of developing prostate cancer, according to a review of published reports. But the team who conducted the review says the exact mechanisms behind this association are not known.

“We conclude that dietary fat may indeed be related to prostate cancer risk, although the specific fat components that are responsible are not yet clear,” conclude Dr. Laurence Kolonel and colleagues at the University of Hawaii in Honolulu. The findings are published in the March 3rd issue of the Journal of the National Cancer Institute.

An estimated 200,000 US men will develop prostate cancer this year and 37,000 will die of the disease, according to the American Cancer Society. Prostate cancer is the second leading cause of cancer deaths in men, after lung cancer.

Many studies have noted an association between high-fat diets and an increased risk of prostate cancer. Kolonel's team reviewed scores of studies focused on the meat-cancer link, and conclude that men who eat a lot of meat and dairy products do appear to have a higher risk of prostate cancer compared with men who eat less of these foods.

However, the researchers point out that this could mean either that meat and dairy foods are themselves involved in raising risks, or that some other factor in the men's diets put them at risk. For example, the authors explain that “a high-meat/high-fat diet generally entails a lower intake of plant foods that contain possible protective factors against prostate cancer.”

On the other hand, meat contains zinc. The Hawaii team point out that high zinc intake has been associated with raised risks for prostate cancer. Cooked meat also contains suspected carcinogens such as heterocyclic amines.

Finally, the authors speculate that the fat found in meat might affect levels of male hormones, which are known to impact on prostate cancer risk.

Kolonel and his colleagues conclude, therefore, that “research in this area can still be productive and should be encouraged.”

In a related study, researchers at the University at Buffalo, New York, report that plant-based fats called phytosterols may reduce testosterone activity linked to prostate cancer.

Previous studies have suggested that men living in primarily vegetarian cultures have lower rates of prostate cancer compared with men in Western, meat- eating nations.

To help determine the link between vegetarianism and low risks for prostate cancer, the authors fed one group of rats a diet high in phytosterols and another group a normal rat diet.

In rats fed the phytosterol-rich diet, levels of circulating testosterone and related enzymes fell by nearly half compared with rats on the normal diet, the authors report. The researchers note that this reduction in testosterone did not affect sexual function.

High testosterone levels have long been linked with higher risks for prostate cancer. “The combined effect of reducing levels of testosterone and the activity of its two main enzymes suggest a diet high in foods containing phytosterols could help reduce the risk of prostate cancer,” said lead author Dr. Atif Awad in a statement.

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