Upcoming Harvard risk-assessment study finds health increases along with fish intake

by Craig Weatherby and Randy Hartnell

Consumers who try to follow the debate over the relative risks and rewards of eating fish must feel like spectators at a tennis match.

While newly discovered health benefits of the omega-3 fatty acids dominate news reports about fish, these reports usually include caveats concerning mercury. And some advocacy groups get way overheated about the dangers of mercury in fish, making no distinction among species, and ignoring the hefty health benefits of the “pre-formed” omega-3s found only in fish.

Mercury levels vary greatly among species: wild salmon contain some of the lowest levels of any commercial fish, while swordfish, north Atlantic mackerel, shark, and tilefish contain the highest levels of mercury found in any common food.

Environmental mercury comes mostly from coal-burning power plants. It works its way from the air to the planet's waters, and up the food chain into sport and commercial fish species.

There is no question that mercury is a toxin that can damage human brains and nervous systems, or that mercury is especially threatening to the growing brains of fetuses, infants, and toddlers.

However, fish are also the richest source of the beneficial omega-3 fatty acids DHA and EPA, which exert strong anti-inflammatory effects throughout the body.  (Hidden inflammation plays a key role in promoting or exacerbating cardiovascular disease, cancer, diabetes, obesity, and Alzheimer's.)  DHA is also considered essential to the integrity of cell membranes, and formation of healthy brains and eyes.

What's a consumer to do? Minimize fish consumption to reduce mercury intake, and thereby miss out on the myriad benefits of omega-3s?

While this contradictory preventive-health dichotomy appears to pose a cruel dilemma, an incisive new analysis comes down firmly on the side of eating more fish.

EPA advice to pregnant women, young children

This special advice comes straight from the U.S. EPA, and applies to women who are pregnant or may become pregnant, and to young children:

By following these 3 recommen-dations for selecting and eating fish or shellfish, women and young children will receive the benefits of eating fish and shellfish and be confident that they have reduced their exposure to the harmful effects of mercury.

1.) Do not eat Shark, Swordfish, King Mackerel, or Tilefish because they contain high levels of mercury 

2.) Eat up to 12 ounces (2 average meals) a week of a variety of fish and shellfish that are lower in mercury. 

Five of the most commonly eaten fish that are low in mercury are shrimp, canned light tuna, salmon, pollock, and catfish.

Another commonly eaten fish, albacore ("white") tuna has more mercury than canned light tuna. So, when choosing your two meals of fish and shellfish, you may eat up to 6 ounces (one average meal) of albacore tuna per week.

3.) Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas. If no advice is available, eat up to 6 ounces (one average meal) per week of fish you catch from local waters, but don't consume any other fish during that week.

Harvard study finds rewards outweigh risks

Attendees at the Institute of Food Technologists (IFT) hear encouraging news from a seafood nutrition panel that included George M. Gray, Ph.D., Lecturer on Risk Analysis at the Harvard School of Public Health, Executive Director of the Harvard Center for Risk Analysis.

Gray described the findings of a study designed to determine the relative costs and benefits of the omega-3s and mercury in fish.  His team concluded that public health would suffer if people cut their fish consumption in response to scary media stories, while average life expectancy would increase if Americans upped their fish consumption by 50 percent.

According to the National Fisheries Institute, Americans currently consume only five ounces a week of fish high in omega-3s, which less than half the amount (12 ounces per week) recommended by the U.S. Food and Drug Administration.  And some 14 percent of women of childbearing age eat no fish at all, despite the fact that omega-3s are essential to proper brain and eye development in a fetus.

Other benefits of omega-3s include cancer-prevention, reduced risk of heart attack and stroke, optimal eye and respiratory health, and reduced risk of depression.

As Dr. Gray told the Newswise wire service, “Our results surprised us. While the numbers themselves can vary, the end result—a net gain in public health when fish consumption goes up and a net loss when it goes down—is the same every time.”

Newswise also interviewed Dariush Mozaffarian, M.D. lead author of a recent Harvard Medical School study confirming the strong cardiovascular benefits of fish. Dr. Mozaffarian put the point this way:  “The critical point is that, even with mercury, we're getting an enormous and invaluable benefit from omega-3. Of course, we'd get even more benefit by lowering the mercury content.”

Eat low-mercury fish… and demand deep cuts in mercury emissions

The FDA says that wild salmon are among the species with the lowest mercury counts, and our young, low-weight albacore tuna contain far less than standard canned white (albacore) tuna (Our sardines, halibut and sablefish are also relatively low in mercury).

The real problem is that coal-burning power plants keep pumping more mercury into the air, which ends up in our oceans, lakes and streams.

To help reduce mercury emissions, and switch to alternative sources of power, contact your representative and Senator, and make it clear that you want your air and water cleared of mercury.  It is outrageous that power companies keep getting a pass from Congress when it comes to requirements for cleaner technology.

The Environmental Working Group does some of the best work in this area.  We recommend their eye-opening report, Mercury Falling: An Analysis of Mercury Pollution from Coal-Burning Power Plants,” and encourage you to contribute to their efforts.

Once you have the facts, write to your Congressional representatives. (Physical letters get more attention than emails, but either is worth doing; it's smart to keep your messages short and civil.) To get their contact information, go to the official Web sites at www.house.gov and www.senate.gov.


  • Newswise/Medical News, July 19, 2005. IFT hears Americans not eating enough fish for good health. Accessed online July 20 at http://www.newswise.com/articles/view/513221/
  • Gobin A, Brooks JP, Kwetz B, Scott R, O'Sullivan W, Shaw D, Majkut S, Valentinetti S, Marin A. Northeast States for Coordinated Air Use Management. Economic Valuation of Human Health Benefits of Controlling Mercury Emissions from U.S. Coal-Fired Power Plants. Accessed online July 20 at http://bronze.nescaum.org/airtopics/mercury/rpt050315mercuryhealth.pdf