DESPITE all those talks about some fish containing high levels of toxins (mercury, for instance), medical researchers still love fish, touted to be the last wild meal in the human diet. The biggest reason: It combats a top health threat, according to a recent issue of Reader's Digest.

"If you eat a modest amount of fish, you dramatically decrease your risk of dying from a heart attack," Dr. Dariush Mozaffarian, a researcher of the Harvard School of Public Health, was quoted as saying by the magazine. Findings from 30 large studies conducted around the world show that people who consume just one or two servings of fish per week lower their risk of a fatal heart attack by an average of 36 percent, according to Dr. Mozaffarian.

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That's good news since the Department of Health ranks heart disease as the number-one killer in the Philippines. "The death toll from cardiovascular diseases in the country is about one every seven minutes," said Dr. Philip S. Chua, one of the country’s top cardiologists.

Cardiovascular diseases don't affect the heart itself but also the blood vessel system, especially the veins and arteries leading to and from the heart.

If you have already a heart attack, shifting to a high-fish diet can cut your chances of future deadly attacks by one third. You see, fish contains oil that is nature's richest source of omega-3 fatty acids called eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Omega-3 fatty acids are a form of polyunsaturated fat that the body derives from food. Omega-3s (and omega-6s) are known as essential fatty acids because they are important for good health. The body cannot make these fatty acids on its own so omega-3s must be obtained from food.

An article which appeared in Journal of the American Society for Clinical Nutrition said omega-3 fatty acids in fish oil prevent heart disease by exerting an anti-arrhythmic effect on the heart, by inhabiting the developing of narrowing arteries, by reducing the levels of undesirable lipoproteins in the blood, and by reducing blood clots within intact blood vessels.

"If you heart high blood pressure is caused by hardening of the arteries, heart disease, or high cholesterol, fish oil may be just what the doctor ordered," wrote the editors of Super Life, Super Health. "The higher your cholesterol levels and the worse your heart disease, the better fish oil works to lower your blood pressure."

The American Heart Association suggests that people should eat at least two servings of oily fish each week to help keep their hearts healthy. Best sources of omega-3s are bass (striped), herring, mackerel, oysters, sablefish, salmon, trout (freshwater), and tuna.

But hearts are not the only human part that benefit from fish. Older folks considered fish as "brain food" and now scientists have evidence to back the claim. A 2007 study of nearly 12,000 pregnant women found that children born to mothers who ate more than 340 grams of seafood per week during pregnancy scored six points higher on tests of verbal IQ than kids born to mothers who had other foods on the menu.

What about adults: A study done in Sweden found that young men who ate fish more than once a week scored nearly 11 percent higher on IQ tests than males who rarely ate seafood. And in later years, fish eaters appear to be less likely to develop dementia.

But you ain't heard anything yet. A study published in Biological Psychiatry has shown that omega-3 fatty acids may help prevent depression. Dr. Joseph Hibbeln, who studies the health benefits of fish at the U.S. National Institutes of Health, discovered omega-3 fatty acids can raise the levels of serotonin and dopamine, two brain chemicals that are thought to play a role in depression.

Fish oil appears to have anti-inflammatory properties, and has been researched as a treatment for many conditions including inflammatory bowel disease and rheumatoid arthritis. It also has some preventive effect for Parkinson’s disease.

So when is fish not so good for your health? Almost all fish is contaminated with trace amounts of mercury. While most healthy adults have no problem eliminating the mercury from their bodies, children and women who are pregnant or breastfeeding should avoid some types of fish and shellfish to reduce their risk of mercury exposure.

Fish that contain the low level of mercury are anchovies, catfish, clam, crab, haddock, hake, herring, salmon, sardines, shrimp, trout (freshwater), tuna, and whitefish. The following have higher content of mercury: swordfish, shark, king mackerel, and tilefish. "Avoid eating them, as possible," experts warn.