Wild salmon (photo courtesy of livesuperfoods.com)

Wild salmon (photo courtesy of livesuperfoods.com)

11/05/2007

A Healthy Choice That's Run its Course

by Andrea Carter

What a tangled food web we weave.  As our appetite for seafood continues to deplete the ocean’s fish populations, mercury, pumped into the environment from the coal burning industry, travels through the food web  and concentrates in the world’s fish, making them less safe to eat. 

Fish is replaceable in a nutritious diet. So given the environmental and health concerns, it may be worth it for people to lay off the fish, at least for a while.

Fish became a healthy fad in the 1970’s when scientists discovered that Eskimos had a lower incidence of heart disease compared to Western countries, even though they ate a diet of whale and seal blubber. The fat is full of omega-3 fatty acids from the fish the large mammals eat.  Fish is a good source of protein, and studies show the heart friendly omega-3 fatty acids can lower blood pressure and blood triglyceride levels and prevent arteriosclerosis. Studies show that eating one to two servings of fish each week can reduce the risk of death from heart disease by at least fifty percent.

But nutritionally, fish is not the only game in town.  American cuisine offers a range of other good proteins, both meat-lean chicken and pork and vegetarian soy products. Also, omega-3 fatty acids are found in other foods, such as flaxseed, walnuts and vegetable oils. Some packaged foods are high in this good fat, such as Hellmann’s mayonnaise. The 1997 Lyon Heart Study found that eating a diet high in canola oil could cut the risk of death from heart disease by seventy percent.

“Let’s put it this way. There are plenty of people allergic to fish who have long lives.” says Dr. Jane M. Hightower at the California Pacific Medical Center and Geraldine Brush Research Institute.

In addition to omega-3 fatty acids, fish meat also contains mercury absorbed from the environment, which is not a healthy part of the diet.  Although mercury is found naturally in the soil from volcanic eruptions, scientists estimate that seventy to eighty percent of the mercury in the land came from industry.

A study published in the Proceedings of the National Academy of Sciences this September says that mercury released in the air from coal burning industry travels into freshwater fish rapidly. Scientists tracked a mercury isotope they added to a lake to simulate rainfall. During the three-year study, mercury isotope levels in fish increased by thirty to forty percent. Mercury travels through the food web in the form of methyl mercury. Fish take up this toxic form from the food they eat. The path of mercury emissions to ocean fish is still being investigated. But mercury is rampant in ocean fish as well, especially those fish on top of the food chain, such as tuna and swordfish.

“You wouldn’t be able to find a fish without some mercury in it,” says Robert Mason at the Department of Marine Sciences at the University of Connecticut.

Although it’s unclear if mercury harms the fish, it is a poison for animals that eat them.  Methyl mercury sticks to cell proteins, binding them up, so they can’t do their job.  Developing cells are the most vulnerable. Animals that eat fish can have reproductive problems. Birds can have lower egg numbers while human fetuses or children exposed to mercury can have developmental delays.

But mercury can also make healthy adults sick. High blood mercury levels can cause fatigue, headaches and muscle or joint pain and more seriously, cardiovascular disease, autoimmune disease and infertility. In a 2003 study, Hightower tested the blood mercury levels of patients who had either complained of mercury-related symptoms, or those who ate a lot of mercury- rich ocean fish. She found that eighty-nine percent of this group had blood mercury levels higher than that recommended by the Environmental Protection Agency and the National Academy of Sciences.

“There is a problem that people are not getting adequate information,” says Hightower.

Conflicting information from different sources can cause confusion. Consumers must read the fine print to get the right information. The Journal of the American Medical Association says six ounces of fish each week is all that’s needed for heart health, while the FDA and American Heart Association recommend up to fourteen ounces of fish per week as long as it’s a low mercury fish.

Another reason to say no to ocean fish is that there are not enough of them to eat. Large fish populations such as tuna, shark and grouper have dropped by ninety percent compared to fifty years ago.  Meant as a warning rather than a literal prediction, a model study published in Science in 2006 estimated that there would be no fish in the sea by 2048 if current fishing conditions continue. So perhaps it would be better to stop eating fish?

“It would be [an] ideal thing that nobody eat fish, but it is not realistic, and it’s not a policy of mine,” says Dr. Carl Safina, director of the Blue Ocean Institute a nonprofit dedicated to ocean conservation.

Safina’s policy is to choose fish that have sustainable numbers for the dining table. The Blue Ocean Institute and Monterrey Bay Aquariums put out guides for the seafood consumer on which fish to eat.  According to Safina, people’s choices can cause a shift in the market. For example, Wal-Mart is considering selling only sustainable fish in the next five years.

All practicality aside it may be hard for the world to give up fish. Tuna sandwiches are a mainstay in American cuisine as is sushi in Japan. For many fish simply tastes good.

“Fish adds a new window of opportunity for variety in cuisine,” says Carl Fantasia, owner of the New Deal fish market in Cambridge.

Everything in moderation says nutritionists and doctors when it comes to diet. Following this advice may be the best compromise in addressing the health and environmental concerns of eating fish.