A nutritious guide to understanding the health benefits of fish

There are more than 20,000 species of fish in the world's waters, although we eat only a small number of varieties. And we don't eat them often enough, doctors say: solid research shows that people who eat fish regularly have healthy hearts — and minds. But does fish come with side effects that stink?

High levels of toxins in some fish represent a genuine concern. But fish's benefits outweigh the threat.

• Just a few years ago, this would have been a no-brainer: of course you should eat fish. People who eat at least a few servings of fish per week have far fewer heart attacks, fewer strokes and fewer fatal arrhythmias, or irregular heartbeats, than people who don't eat fish. What's more, developing brains require the fatty acids found in fish.
• One recent study found that children born to women who ate at least two servings of fish a week during pregnancy had higher IQs, were better behaved and were less likely to have other developmental problems.
• Unfortunately, the sea of good news about fish has turned murky in recent years. Several high-profile reports revealed that some varieties of fish contain high levels of contaminants, including mercury and the industrial toxins dioxins and polychlorinated biphenyls (PCBs).
• Studies have linked exposure to these toxins to cardiovascular problems, damage to the nervous system and other health threats. Suddenly, many consumers found themselves pausing at the fish counter or hesitating before opening a can of tuna, wondering: "Is this stuff safe?"
• To find the answer, researchers combed through stacks of studies, government reports and other scientific literature on fish and human health. The bottom line: eating fish far outweighs any accompanying risks. The study determined that people who have just one or two servings of fish each week lower their risk of a fatal heart attack by 36 percent and have a 17 percent reduced risk of dying from any cause, compared to people who don't eat it.

The US Food and Drug Administation and Environmental Protection Agency advise women who are pregnant or may become pregnant, as well as young children, to limit themselves to two servings of fish per week.

• They should also avoid fish that tend to contain high levels of mercury, which include king mackerel, shark, swordfish, marlin, orange roughy and tilefish.
• Likewise, people in these groups should eat no more than 175 grams (six ounces) per week of canned albacore tuna, which is moderately high in mercury.

Overall, fish is a tasty and nutritious part of any diet. Consider this guide and incorporate fish into your meals to take advantage of the healthy benefits.