Eating Fish: Good for You or Not?

Fish presents a quandary for even the savviest of shoppers or diners, buffeted by conflicting reports on health benefits and environmental impact, not to mention food-borne illnesses. The answers aren’t black and white, according to public health, nutrition, and conservation specialists. Some worry that fear-mongering gives fish - wild or farmed - a bad rap, denying people a good source of protein. Others contend that some species are so contaminated - like some kinds of tuna used in sushi - they should almost never be eaten.

The health issues boil down to omega-3 fatty acids on the positive side and contaminants on the negative side. Environmental concerns center on the sustainability of fish stocks and the effects that ocean fishing and aquaculture have on other animals and ecosystems.

Many fish are abundant in omega-3 fatty acids, especially oily fish such as salmon and bluefish. Omega-3s have been linked to a lower risk of cardiovascular disease because they appear to prevent dangerous heart rhythm changes, lower blood pressure, keep blood vessels healthy, and reduce inflammation. A growing body of evidence also suggests omega-3s play a role in children’s early neurological development, and perhaps in delaying cognitive decline late in life.

On the down side, both freshwater and saltwater fish may contain PCBs and dioxins because the waters they swim in have been polluted. PCBs have been tied to cancer in laboratory animals, but the connection to cancer in humans is less clear. In a 2007 report, the Institute of Medicine called the risk “overrated.’’

Mercury, also an industrial pollutant, has been directly implicated in severe neurological problems. Not all fish pose the same risk, but larger, predatory fish can have levels so high that in 2004 the US Environmental Protection Agency and the US Food and Drug Administration warned pregnant women and young children not to eat four kinds of fish: shark, swordfish, king mackerel, and tilefish. They were encouraged to make other fish species a part of their diet - including shrimp, canned light tuna, salmon, pollock, and catfish - up to twice a week.

Eric Rimm of the Harvard School of Public Health says the government’s prudent mercury message has been lost amid unjustified panic. He led a scientific review of research weighing the benefits of fish against its risks. For all people, he and his Harvard colleague Dr. Darius Mozaffarian concluded, the cardiovascular benefits were 300 to 1,000 times greater than the risk of cancer from consuming fish. Their 2006 paper reported PCBs and dioxins in beef, chicken, and eggs at levels similar to what were found in farmed salmon.

“The evidence comes down pretty strongly on the side of the fact that fish and/or omega-3 fatty acids are beneficial in reducing the risk of heart disease,’’ he said. “A lot of what we eat contains contaminants. I think we’ve looked at fish with a much larger magnifying glass.’’

Alice Lichtenstein, a professor of nutrition science and policy at Tufts University, says wild and farmed salmon have similar omega-3 content. Even fish low in omega-3s are a good choice, as long as they aren’t smothered in breading and fried in partially hydrogenated oil.

“Fish still is a very good low-saturated fat and low-calorie choice, and it is usually used to displace food higher in saturated fat and calories, whether it’s steak or quiche,’’ Lichtenstein said, adding that cardiovascular benefits probably arise from both omega-3s and not eating less nutritious choices.

While Lichtenstein says we cannot ignore contaminants in fish, she believes those contaminants get a disproportionate amount of attention compared with the much greater risk of cardiovascular disease. She advises eating a variety of fish, rather than a steady diet of just a few species.

Where the fish come from can be important for environmental health, says Lydia Bergen, director of conservation at the New England Aquarium. There are good and bad ways to farm fish, just as there are good and bad ways to catch fish in the ocean.

Shellfish farming is one of the best environmental options, she said. Blue mussels, clams, and oysters are grown in the ocean, and require no fishmeal - food made from other fish - so they have a low environmental impact. As a whole, the ratio of fishmeal required to produce a pound of fish has gone down over the last decade to less than 1 pound, putting less pressure on fish stocks, but for farmed salmon the ratio is about 5 pounds of fishmeal per pound of salmon, according to a recent paper from North Carolina State University.

“Salmon has gotten a bad rap,’’ Bergen said. “I really do like to point out that most of our protein is farmed. Pigs and chicken are bigger consumers of fish meal than seafood,’’ requiring about 10 pounds of meal to yield one pound of meat.

Marine conservationists are also concerned with whether fish farms pollute the environment with their waste streams. And less well-managed farms allow fish to escape into the ocean and compete with wild fish for food.

In the ocean, what matters are the health of the fish populations - are there enough to reproduce so people can keep eating them - and their habitat. Some fishing methods, such as trawl nets that drag across the ocean bottom, are more likely than others to have bycatch, the term for pulling in unintended animals such as sea turtles or whales or endangered species.

Consumers should ask how and where a fish was farmed or caught.

Fish caught in US waters - particularly in areas such as Alaska, certified by the marine stewardship council - are better environmental bets. “By asking questions, it shows the vendor that you care about where your food is coming from,’’ Bergen said. “If they don’t know the answer, they should.’’

The New England Aquarium is working directly with some vendors, including Stop & Shop and its parent company Ahold, to take some of the burden off the consumer.

“We’re finding that more and more of our consumers are starting to ask questions and paying attention,’’ said Tracy Taylor, senior seafood buyer for Stop & Shop’s 720 stores in New England and the mid-Atlantic states. She has visited shrimp farms as far away as Indonesia and Thailand with an aquarium specialist, and urges higher standards for waste treatment, feed, and overall health of the shellfish.

Restaurateur Roger Berkowitz of Legal Sea Foods is blunt about health and sustainability. “I’m in the business of selling fish. I have to be a conservative,’’ he said. “If I’m not, I’m not going to be in business too much longer.’’

He advises consumers to challenge their server or fish vendor, asking if their farmed salmon were fed organic fishmeal or whether the scallops are “wet’’ - soaked in chemicals to make them plumper - or “dry.’’ They should try other kinds of fish, such as wolf fish, ocean catfish, or redfish, to ease pressure on species like Atlantic cod, whose stocks have not rebounded as quickly as people hoped.

Careful consumers can be forgiven for their confusion, when they find the same species of fish appearing on all three lists of environmentally good, bad, and in between put out by the Monterey Bay Aquarium.

Porter, the Central Massachusetts woman, said she might eat fish more often if she knew more about it. But “it’s a balancing act,’’ she said. “We make all these choices, but then we eat M&Ms with dye in them.’’ 

-From: “Fishing for facts; Good for your health, or toxic to you and the environment: It’s hard to know what fish to eat” by Elizabeth Cooney, The Boston Globe, December 14, 2009, http://www.boston.com/news/health/articles/2009/12/14/conflicting_reports_raise_health_quandary_for_consumers_of_fish/ retrieved 12/14/09.

 

12/09