Fish Protects Against Cancer and Heart Disease

In March, 2002, a group of Swedish scientists discovered a relationship between eating fish and preventing cancer. Women who ate six to eight ounces per week of fatty fish, such as herring and salmon, had forty percent less cancer of the endometrium (uterus) than those who ate just lean fish or no fish at all. "Our results suggest that the consumption of fatty fish, but not other types of fish, may decrease the risk of endometrial cancer," they wrote .

The researchers speculated that the omega-3 oils found in fatty fish were protective. Other kinds of cancer may be similarly prevented. Last year, an article in The Lancet showed that men who regularly ate moderate to high amounts of fish had about half the chance of developing prostate cancer than those who didn't. "Fish consumption could be associated with decreased risk of prostate cancer," scientists reported (Lancet 2001;357:1764-1766).

Protecting the Heart

Eating fish may also decrease the risk of a heart attack. Last November, American scientists published a huge survey of men in Shanghai, China. Older men who ate at least 7 ounces of fish or shellfish per week had 59 percent fewer fatal heart attacks than those who ate less than two ounces (Am J Epidemiol 2001;154:809-16). Two recent articles in top journals have confirmed these claims. The first was a study of 22,000 male doctors. Researchers compared physicians who had died of sudden heart attacks to others who maintained normal hearts. In particular, they compared bloodstream concentrations of omega or n-3 fatty acids, which are primarily found in fish oils. The men who had the highest levels of omega-3s had only one-fifth the risk of sudden death as those who had the lowest levels. (N Engl J Med 2002;346:1113-1138).

A second study, published in the Journal of the American Medical Association, looked at the health records of 85,000 female nurses. Researchers found that the more frequently a woman ate fish, the less likely she was to suffer a heart attack or to die of heart disease. Those who ate fish once a week had a 30 percent lower risk of heart attack or death as those who never ate fish (JAMA 2002;287:1815-1821).

My recommendation is to eat six to eight ounces of fatty fish per week. That said, I realize there are difficulties in doing so. Healthful fish has become difficult to procure. In January, 2001, the FDA cautioned pregnant women, and those of childbearing age, not to eat shark, swordfish, king mackerel and tile fish. All of them are contaminated with methyl mercury, an extremely dangerous form of mercury, which can cause birth defects. Lactating women and small children were also advised to steer clear of these fish. What these four fish have in common is that they are at the top of the oceanic food chain. "These long-lived, larger fish that feed on smaller fish accumulate the highest levels of methyl mercury," said the FDA, "and therefore pose the greatest risk to the unborn child."

The FDA further advises these women "to select a variety of other kinds of fish, including shellfish, canned fish, smaller ocean fish or farm-raised fish" (FDA Consumer Advisory, March 9, 2001). The FDA's position is that, although childbearing women and young children should avoid these fish, it is safe for all others: "Most people have no reason to limit their fish consumption." This is strange, considering the vast data on methyl mercuryÕs harm to adults as well as children.

According to Maine's Natural Resources Council, the safest fish are haddock, cod, hake, flounder, pollock, Atlantic salmon, herring, smelts, clams, shrimp, scallops, lobster (except the tomalley, which can contain dioxin) and canned "light" tuna (safer than canned "white" tuna). The safest freshwater fish are brook trout, yellow perch and landlocked salmon. (Avoid salmon that has been treated with antibiotics or dyed with artificial colors.)