STUDY indicates oily fish might ward off prostate cancer

Thursday, May 31st 2001, 12:00 am
By: News On 6

LONDON (AP) _ Eating even moderate amounts of oily fish such as mackerel, salmon and sardines might cut the risk of prostate cancer in half, new research suggests.

Omega-3 fatty acids, plentiful in dark, oily fish, are known to fight heart disease. They also have shown promise in protecting against cancers of the colon, rectum and ovary.

Previous studies have shown fatty fish oils can impede the growth of prostate cancer cells in laboratory dishes and in animals. In another study, prostate cancer was found less frequently in men who had high levels of fatty acids in their blood.

Now, a new study, published this week in The Lancet medical journal, found that Swedish men who ate greasy fish only occasionally or not at all were twice as likely to develop prostate cancer as those who made it a moderate or large part of their diet.

Dr. Regina G. Ziegler, a nutritional epidemiologist at the National Cancer Institute, was cautious about the Swedish findings. The study was financed by the Swedish Cancer Society, The John D. and Catherine T. MacArthur Foundation and the Swedish Council for Planning and Coordination of Research.

``It's a provocative study,'' said Ziegler, who was not involved with the research. ``But there could be other dietary patterns that go along with eating very little fish that could be at work here.''

People who seldom or never eat fish tend to substitute with more red meat, Ziegler said, and scientists believe animal fat _ butter, cream, beef, pork and processed meats _ may encourage prostate cancer.

``Is the fish really protective, or is red meat causing the cancer?'' Ziegler cautioned.

Also, Swedish men eat a lot of oily fish, so there weren't many in the group who ate very little of it. That means that although the study involved thousands of men, the effect seen was driven by a small number of men with unusual eating habits. With such a small sample, it is difficult to rule out the possibility that it was not the fish itself, but something else about the men who were not big fish eaters, Ziegler said.

Prostate cancer strikes about 21 out of every 100,000 men worldwide, according to the World Health Organization. It is most common in North America and northwestern Europe.

The study involved 6,272 men followed for about 30 years. During the study, 466 of them were diagnosed with prostate cancer, on average when they were 76 years old.

The link between the fatty fish and a reduced frequency of prostate cancer was even stronger after the results were adjusted to account for the influence of other eating habits, a genetic predisposition to prostate cancer and smoking, drinking and exercise habits, the study said.

``We're only talking about a moderate intake. This would be about two or maybe three servings a week. That is very manageable,'' said one of the researchers, Alicja Wolk, professor of epidemiology and nutrition at the Karolinska Institute in Stockholm, Sweden. ``What is also important is that the fattier the fish it is, the less you have to eat to get the same benefit.''

Sardines have the most omega-3 oil in them, while the concentration in tuna is quite a lot less, Wolk said, adding that it doesn't matter if the fish is canned.