No wonder it’s hard to know what kind of fish to eat

Is anything more confusing for food shoppers than buying fish? Mercury contamination versus omega 3 fatty acids? Farmed? Wild caught? And what’s behind price variations of $15 a pound?

It’s no wonder even savvy shoppers walk away from the fish counter empty-handed.

There is no simple advice out there that takes into account health, the environment and economic effects of consumers’ fish choices, says Emily Oken, associate professor in population medicine at the Harvard Medical School.

She and colleagues reviewed the advice from government and nonprofit groups such as the Monterey Bay Aquarium, which issues a pocket guide to buying and avoiding fish based on environmental standards.

Fish, they wrote in a recent issue of the journal Environmental Health Perspectives, is a “rich source of protein and other nutrients,” but some people should limit fish consumption to avoid contamination from methylmercury and other toxins. In addition, if everyone ate according to federal recommendations, there would not be enough fish, Oken said in a phone interview.

“For example, farm-raised salmon is … promoted for its nutritional benefits, but environmental groups consider it a ‘fish to avoid’ because salmon aquaculture may adversely impact ecosystem integrity and wild fish stocks and relatively high levels of PCBs have led to concerns about cancer risk,” the researchers wrote.

“We suggest developing a list of fish to eat, and those to minimize or avoid, that considers these multiple perspectives and not solely the health effects of contaminants and nutrients,” the researchers wrote. “This list should include links to more detailed resources that can be used by those wanting more information about individual fish types, or wishing to optimize one or more parameters.”

For now, Oken says, consumers should “take stock of where they are personally” when making decisions. For example, a pregnant woman might make different choices than a man at risk for heart disease. She would care about the possibility of mercury contamination; he would care more about the nutritional profile.

The state of affairs over fish is not unlike fruits and vegetables years ago, when the news was full of stories about pesticide residues found on fruit and the organic alternatives. Federal officials and others were quick to note that eating no produce was not a good alternative.

People might keep in mind that those who eat one to two servings of fish a week are healthier than those who eat no fish, Oken said.

Oken said she hopes the research can at least make people more aware of the advice they receive. She recommends: “Take a step back and ask from what perspective is this advice coming.”