Fatty Fish May Prevent Prostate Cancer
Study finds higher rates in those who don't partake
Everyone knows that eating fish rather than red meat helps prevent heart attacks and strokes, but a Swedish study now indicates that fish protect against prostate cancer.
The study, which included more than 6,000 Swedish men and covered three decades, finds that "men who ate no fish had a twofold to threefold higher frequency of prostate cancer than those who ate moderate or high amounts," says a report in the June 2 issue of The Lancet.
The protective effect appears to come from one specific class of nutrients in fish -- omega-3 fatty acids, says Alicja Wolk, professor of nutritional epidemiology at the Karolinska Institute in Stockholm and a member of the research team.
Fish rich in those fatty acids include salmon, sardines, mackerel and herring, Wolk says. They are traditional staples of the Scandinavian diet, she notes. Studies have shown that omega-3 fatty acids inhibit the growth of prostate cancer cells grown in laboratories, but the Swedish study is one of the few to measure the effects in real life.
The study started in 1967 when 6,272 men filled out a 107-item questionnaire. They were asked about their smoking habits, alcohol consumption and physical activity, and how much fish they ate. Analysis of the 466 cases of prostate cancer that occurred in the group found a direct relationship between the amount of fish in the diet and cancer risk, Wolk says.
The study indicates that it isn't necessary to eat a lot of fish to gain the protective benefits. "It seems that twice a week would be good, maybe even once a week if you are eating fatty fish," Wolk says.
Some fish, including tuna, don't fall into the fatty category, she says. The nose can help tell whether a species of fish is rich in omega-3 fatty acids because of the pungent oils. Just eat "anything that smells not too good," she says.
Omega-3 fatty acids, which get their name from their molecular structure, are believed to exert their protective effect by reducing the concentration of cancer-enhancing hormones. That protective effect could apply to other cancers, she says.
"We are studying other hormone-dependent cancers now -- breast cancer, endometrial cancer," Wolk says.
Dr. Laurence N. Kolonel, deputy director of the cancer research center at the University of Hawaii, who has done several studies on diet and prostate cancer, says "it is logical that these long-chain fatty acids might protect against cancer."
Diet does seem to affect prostate cancer risk, Kolonel adds. His studies have linked increased risk to saturated fatty acids, the kind found in red meat, and a reduced risk with fruits, vegetables and legumes such as beans.
He raises one small warning flag. There's always the chance that the protection comes not directly from fish in the diet. "Lower consumption of something else might be doing good," he says.
On the other hand, "I don't know of any studies that have found an adverse effect of fish consumption," Kolonel says.
Thanks to HealthScout, Edward Edelson
Cancer Epi Bio & Prev, 9/02
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