There’s something, er, fishy about the new Dietary Guidelines for Americans 2010. Unlike the 2005 version, the newly updated edition of the federal government’s official guide to healthful eating lists increasing seafood intake among its key recommendations.

By “fishy,” I don’t mean suspicious. Besides being delicious, fish and shellfish, which together constitute “seafood,” can confer lasting health benefits.

How much?

8 oz. The amount of seafood most of us should eat each week. That’s two four-ounce servings, more than twice what most of us typically manage (3.5 ounces).

12 oz. The weekly amount recommended for women who are pregnant or breast-feeding.

4 oz. The amount of fish in a small can of tuna, which means an ordinary tuna sandwich gets you halfway to your weekly goal.

The benefits

Like red meat and poultry, fish provides the protein essential for maintaining healthy muscles and other tissues. Most of us get more than enough protein. What really makes fish worth eating are its omega-3 fatty acids. New research shows that these healthful fats may help prevent age-related macular degeneration, a disease that impairs vision. But their benefits extend far beyond that.

Heart health. Omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), help prevent cardiovascular disease and sudden cardiac death. Penny Kris-Etherton, professor of nutrition at Penn State, says these healthful fats can reduce heart arrhythmia, the leading cause of sudden cardiac death. The effect can take hold mere weeks after a person adds more fish to his diet, she says. Omega-3s may also lower triglycerides and blood pressure and prevent blood clots that can cause stroke.

Child development. Omega-3 fatty acids contribute to fetal growth and brain development in early infancy, says Bethany Thayer, a spokeswoman for the American Dietetic Association. When women consume omega-3s — especially DHA — from at least eight ounces of seafood per week, the dietary guidelines say, their babies may have heightened visual and cognitive development.

Kris-Etherton adds that research shows kids who eat more fish may have slightly higher IQs than those who eat less. “A couple of IQ points, you question whether that can make a big difference,” she says. “But it might have some bearing on test-score results.”

How to eat more

Can it. For convenience, you can’t beat canned tuna and salmon (which also are good sources of Vitamin D and, if you buy the bone-in kind, calcium, Kris-Etherton says). Keep in mind, though, that if you limit yourself to these you’ll be getting more sodium than you need and missing out on the wide range of options in the fresh-seafood case.

Try milder fish. Don’t like fishy taste? Try mild-flavored fish such as cod, flounder, sole and tilapia, which take well to baking, poaching or steaming, Thayer says, more so than grilling. But she notes that these don’t deliver as big a dose of omega-3s as fattier fish.

Go beyond the fillet or steak. You can add fish to soups or salads, Thayer suggests. Get kids to eat more fish with homemade fish stripsor fish tacos. Or simply coat strips of cod or haddock in seasoned bread crumbs and bake them in the oven. Thayer herself is partial to salmon topped with fruit salsa. (You’ll notice that nobody suggests battering and frying, which adds unneeded calories and often unhealthful fat.)

Consumer concerns

Best for omega-3s. Some seafoods have more of these than others. The best are: salmon (wild and farmed) Pacific oysters, anchovies, herring, sardines, trout, and Atlantic and Pacific mackerel.

Mercury. Some people avoid fish for fear of consuming methyl mercury, which may harm the developing nervous system of an unborn baby or young child. Some fish contain more mercury than others, including large fish such as albacore tuna that “are great big and hang around the ocean a long time, eating smaller fish,” says Kris-Etherton.

Pregnant women in particular should steer clear of the top four mercury-containing fish: tilefish, shark, swordfish and king mackerel (also known as golden bass). As for tuna, the dietary guidelines say women who are pregnant or breast-feeding can eat any kind of tuna they like but should stick to no more than six ounces of white tuna per week because it contains more mercury.

Cholesterol. Shrimp is a “very lean source of protein,” Thayer says, but some people shy away because it is loaded with cholesterol. (It’s also lower in omega-3s than other seafood.) Thayer and Kris-Etherton agree that the science is fuzzy on how eating shrimp affects cholesterol levels in your body. American Heart Association guidelines call for consuming less than 300 mg per day of cholesterol; four ounces of shrimp deliver about 160 mg.

Safety and freshness. Cook fish until its internal temperature measures 145 degrees on a food thermometer, Thayer advises. Just checking to see if it’s flaky isn’t good enough. And the best way to tell whether fish is fresh is to give it a sniff. “If it smells fishy, it’s probably not fresh,” she says. “It should have just a faint smell of the sea.”

This column is part of a series about incorporating the Dietary Guidelines for Americans 2010 into your diet.