a fish tale

You've heard the advice: Eat fish and stave off heart disease, cancer, and even depression. But just any fish won't do. Here is how to get your body what it needs.

THE MORE WE LEARN ABOUT THE BENEFITS of omega-3 fatty acids, the more we might decide to like fish--the best source of omega-3s. Research shows that omega-3s can reduce the risk of heart disease and high blood pressure, prevent blood clots, protect against cancer, and help the brain work well. They may even alleviate depression.

"It is incredible the ways in which omega-3s affect our metabolism and ultimately our health," says Joyce A. Nettleton, Ph.D., a nutritionist and director of science communication at the Institute of Food Technologists in Chicago. But eating them occasionally won't do, she says. "You need omega-3s on a regular basis."

It might seem easy to get this nutrient in your diet: Just make sure you eat fish a few times a week. But it isn't quite that simple. First, not all fish are equally endowed with omega-3s. Second, some species of fish are contaminated with toxic chemicals, so if you eat them in the amounts necessary to get the omega-3s you need, you may be at risk from the chemicals. Third, even if you find clean fish and eat plenty of it you still may not be getting enough omega-3s, because it's not just the total amount of omega-3s in your diet that's important, but also the ratio of omega-3s to another group of fatty acids, the omega-6s. (If your diet is at all typical, you consume a lot more omega-6s than you do omega-3s.)

Complicated? Yes, a little. Impossible to get enough omega-3s without the help of a biochemist? No, not at all. Here are four simple steps to help you include this crucial nutrient in your daily diet.

Experts have different opinions about the ideal daily amount of omega-3s to eat, but the ones we consulted on average suggested between I and 2 g. Because some fish contain a lot of omega-3s and some not so much, you need to be aware of which fish are the richest sources (see "Eat Your Fish," right). Shrimp, to take one example, is the second most popular seafood among Americans, according to the National Fisheries Institute, but it contains a relatively small amount of omega-3s; a 3-ounce serving contains only 0.4 g of omega-3s. On the other hand, the seafood Americans eat the most of--tuna--fares much better; the albacore and bluefin species contain about 1 g of omega-3s in a 3-ounce serving.

HOW TO DO IT Keep handy a list of the types offish that are rich in omega-3s and eat those fish often.

2. GET THE RATIO RIGHT Both omega-3s and omega-6s are polyunsaturated fats and both are needed for good health (for instance, they aid in transferring oxygen throughout the body). These two families of fatty acids also work together. For example, when broken down omega-6s can lead to increased blood clots and high blood pressure; omega-3s counter these effects. However, these fatty acids only work together effectively when present in the proper ratios. Omega-6s also compete with omega-3s for absorption into your cells. Therefore, if your diet includes too many omega-6s, you probably won't be able to eat enough fish to get the omega-3s you need.

An optimum ratio of 6s to 3s is 1-to-1, but a ratio of up to 4-to-1 is still considered healthy. The average American's ratio is 10-to-1, and with many people it reaches upward of 20-to-1. That's because omega-6s are present in numerous popular foods, including chicken (especially with skin), meats (notably pork), eggs, many nuts (such as almonds and pecans) and seeds (such as sesame), and most vegetable oils.

A simple way to help balance your 3s and 6s is to choose the right cooking oil. Oils such as corn, safflower, and sunflower--the very oils that for years nutritionists said were good for us--are loaded with omega-6s. Corn oil has about 82 times as many omega-6s as omega-3s. Olive oil is a better choice. Olive oil is a monounsaturated fat that contains omega-9s, a third kind of fatty acid that does not compete with omega-3s for absorption into your cells. Or you also could switch to a more balanced oil, such as canola (for more information, see "The Balancing Act").

HOW TO DO IT Reduce the amount of omega-6 fats you consume by replacing corn, safflower, sunflower, and peanut oils with olive or canola oil. Also, cut back on consumption of pork, chicken, and eggs.

3. EAT CLEAN FISH Tests by federal authorities show that certain species of both freshwater and saltwater fish contain toxins--mercury, dioxin, DDT, and PCBs, to name a few--that have been linked to serious health disorders. You can take steps to reduce your potential exposure to these pollutants in the following ways:

* Choose smaller fish within a species because they typically are younger and haven't been exposed to toxins for as long as the older, bigger fish, advises Ken Gall, a seafood expert with Cornell University in Ithaca, N.Y. If you are buying filleted fish, consider the circumference of the fillet in comparison to the rest of the fillets within a species: Generally, the larger the fillet, the older the fish. Of course, this method only works for fish that are cut into whole fillets. You could also ask your local fish marketer for guidance with this.