Seafood's Benefits Outweigh Risks

(CBS/AP)  Eating seafood twice a week is good for your heart and generally outweighs the risk of exposure to mercury and other dangerous contaminants, the Institute of Medicine said Tuesday.

Even so, the government needs to help consumers figure out which seafood is safer, an Institute report said.

"The confusion may have scared people out of eating something that is beneficial for them and maybe for their offspring," said Jose Ordovas, a Tufts University researcher and member of the report committee. "Our goal was to put both things in perspective and see where is the balance."

"On one hand, you know that it's an excellent source of protein, it's a healthy food. And on the other hand, there is that concern of too much mercury and some fish have a lot of mercury so it's a little confusing," Mary Cannon, who is pregnant, told CBS News correspondent Sharyn Alfonsi.

The findings from the institute, which advises the government on health policy, are in line with widely accepted government advice that eating fish and shellfish may reduce the risk of developing heart disease, the leading cause of death in the United States.

"The average person can consume more fish than they do," Susan Krebs-Smith of the National Cancer Institute said at a press conference.

Interestingly, researchers said it's unclear how eating fish fights heart disease. It may be that beneficial omega-3 fatty acids offer some protection. Or the answer may be simpler: that people eat less saturated fat and cholesterol when they choose leaner seafood instead of fatty cuts of meat.

Americans generally eat too much saturated fat and cholesterol and too little of the good omega-3 fatty acids, the report said. Evidence shows that eating seafood rich in omega-3s can contribute to vision and cognitive development in babies and help expecting moms carry babies to term, researchers said.

The Tuna Foundation and other industry groups issued a statement saying the report tells consumers not to let fears of mercury exposure stop them from enjoying the nutritional benefits of regular fish consumption.

Critics said the report will only worsen confusion about which people should avoid which fish.

Environmental and conservation groups say it should have listed "good fish" and "bad fish," which the researchers said would be too difficult.

Seafood is the main source of people's exposure to methylmercury, which is linked to learning disabilities and developmental delays in children and to heart, nervous system and kidney damage in adults.

"This report is not balanced, and it's taken on more of an advocacy role, rather than a balanced presentation of facts," said Gerald Leape of the National Environmental Trust. "It's a real disservice to consumers."

Critics were also alarmed that the report offers the same guidance for pregnant women as for young children.

"They seem to be unaware that children are smaller than adults," said Jean Halloran, director of food safety at Consumers Union, which publishes Consumer Reports magazine. "That advice, which they have featured prominently, could result in young children getting excessive doses of mercury."

For pregnant women and children younger than 12, the report said:

They may benefit from eating seafood, especially seafood with higher amounts of omega-3 fatty acids.

They may eat six to 12 ounces of seafood a week. That can include up to six ounces of albacore tuna.

They should avoid big predatory fish such as shark, swordfish, tilefish or king mackerel, which have higher mercury levels.

For healthy teenagers and adults and those at risk of heart disease, the report said eating seafood may reduce the risk of heart disease. If people eat more than two servings of seafood a week, they should be sure to eat different kinds of seafood to reduce the risk of exposure to contaminants, the report said.

While the report does not list "good" or "bad" fish, it does describe broad categories:

Fatty fish like salmon have the highest omega-3 levels but also have more saturated fat and cholesterol and can have higher levels of dioxin and PCBs. They tend to have less mercury.

Shellfish and crustaceans are low in saturated fat but can have moderate amounts of cholesterol and present the greatest risk of microbial infection if eaten raw.

In all seafood, levels of dioxin, PCBs and other contaminants do not pose health risks when eaten in government-recommended amounts.