New studies and survey find public reactions to mercury fears overblown and counterproductive
by Craig Weatherby
Last July, we ran a report on a then yet-to-be-released series of five Harvard-led studies designed to determine the relative risks and rewards of dietary fish.
At the time, the Harvard Center for Risk Analysis released only two of their findings:
First, public health would suffer—thanks to a reduction in omega-3 intake—if people cut their fish consumption in response to misunderstood media stories about mercury contamination.
Second, average life expectancy would likely increase if Americans were to boost their fish consumption by 50 percent.
Now, release of full details from the five Harvard-led studies and the results of a new national survey combine to confirm public confusion about mercury and fish, and to caution against adverse health consequences that may stem from well-intentioned 2001 government guidelines: warnings that apply only to young children and to women who are pregnant, nursing, or likely to become pregnant.
The results of the University of Maryland survey, released last week, confirm widespread public confusion about the 2001 mercury advisories, and show that people of all ages cut fish consumption unnecessarily in response.
The survey results show that 45 percent of the 1,040 people surveyed thought the mercury advisory applied to the elderly, while 35 percent thought it was for pre-teens and teenagers, and almost one-third thought it applied to all Americans.
Supporting the findings of the university’s national survey, the U.S. Tuna Foundation reports that consumption of tuna—a focus of many media stories about mercury because canned tuna is the number one source of dietary fish—dropped 10 percent since the government warning. This is another indication that Americans of all ages and genders think the warnings apply to them.
Yet, as lead Harvard researcher Joshua Cohen, Ph.D. told the Boston Globe, referring to the public's confusion, ''If you are not pregnant and not going to become pregnant you shouldn't even be thinking about mercury in fish. The message is people may not always follow advisories in the way you intend... and that can have adverse health risks."
Women's center and Harvard deplore collateral mercury-warning damage
Acting in concert with Dr. Joshua Cohen, leader of the series of Harvard-led fish/mercury studies, the National Women's Health Resource Center (NWHRC) will hold a press conference in Washington, D.C. this October 26 to publicize the research results.
Dr. Cohen and the NWHRC are concerned that Americans—especially women—will likely cut fish consumption in response to mercury cautions intended only for expectant or nursing mothers and women likely to bear a child: cautions which are themselves extremely conservative in their consumption recommendations.
And, if Americans do forgo fish, they will decrease their omega-3 intake dramatically and thereby increase their risk of heart attack, stroke, mood disorders, and Alzheimer’s, among other, less overt health impacts.
Omega-3s and babies... why is fish better than flaxseed?
The long-chain “marine” omega-3 fatty acid called DHA is an essential component of brains and eyes, which explains why long-chain “marine” omega-3 fatty acids are ideal for optimizing fetal and infant development.
There is a short-chain omega-3 fatty acid known as ALA in nuts, seeds (especially flax and hemp), certain vegetable oils, and dark, leafy greens. But mothers’ bodies can only convert a small percent of ALA to DHA: just enough to ensure adequate—but likely not optimal—development. This is why nutrition-savvy pediatricians like Dr. William Sears recommend that expectant mothers eat ample amounts of low-mercury fish.
The reasons for the human body’s preference for long-chain omega-3s may lie in our evolutionary past, when, a growing body of evidence suggests, early hominids gravitated to food-rich rivers, lakes, and ocean shores. These environments offered the abundance of omega-3 rich fish, shellfish, amphibians, and aquatic plants necessary to development of modern humans’ out-sized, heavily omega-3-dependent brains.
The press conference will also reveal the results of the new national survey—which show a decline in American’s fish consumption—and the NWHRC will announce a national "teach in" intended to help women make better-informed decisions about seafood.
What the Harvard-led studies show
The full findings of the five Harvard-led dietary fish risk/reward analyses, and two expert commentaries, were just published online in the online edition of the November’s American Journal of Preventive Medicine.
The research teams wanted to determine whether the benefits of lower mercury exposure among pregnant women outweighed the loss of omega-3 fatty acids from decreased fish consumption. They also examined what would happen if the public reacted inappropriately to government's recommendations regarding mercury and fish.
Some of the results indicate that fears among the general public created by government mercury warnings directed to expectant/nursing mothers may cause many other women—and many men—to cut fish intake, thereby tossing out the health-promoting omega-3 baby with the mercury-fear bathwater:
- Government advisories warning women of childbearing age about mercury exposure appear likely to lead the general public to cut fish consumption, with a resulting loss of substantial omega-3-related preventive health benefits.
- If pregnant women decrease their fish consumption—as they did, unnecessarily, by 17 percent in response to the government’s 2001 mercury advisory—the loss of omega-3 fatty acids during pregnancy would cut the nutritional benefit of eating fish by 80 percent (In other words, that 17 percent reduction in fish intake had an impact on their infants far greater than one would expect).
- If other adults decrease their fish intake by a similar percent, then risks of death from coronary heart disease and stroke would increase among men aged 65 to 74, by about 1 death in 10,000.
- Among all adults, an increase in fish consumption from none to one fish meal per week would substantially decrease stroke and coronary heart disease risks.
The authors also examined what would happen if pregnant women replaced fish high in mercury (swordfish, shark, tilefish) with fish low in mercury, such as wild salmon, low-weight tuna, sablefish, and sardines. They estimated that women's babies would enjoy a tiny, 0.1 boost in their IQ scores.
Conversely, this implies that when mothers eat moderate amounts of even relatively high-mercury fish, the impact on infants’ cognitive development is vanishingly small.
Despite the minuscule size of the estimated impact of fish-borne mercury on IQ levels, it makes sense for women attempting pregnancy, expectant/nursing mothers, and young children to minimize mercury intake.
Mothers can keep their children safe, but still ensure well-nourished brains and bodies by adopting two seafood-selection strategies:
- Choose inherently low-mercury species like wild salmon, sardines, cod, pollock, shrimp, canned light tuna, catfish, and trout.
- Choose safe members of potentially problematic species, such as young, low-weight, minimal-mercury, sablefish, halibut and albacore tuna from Vital Choice.
What's the bottom line? Thanks to its omega-3 content, fish is good for health despite the traces of mercury it contains. Only people at special risk—women attempting pregnancy, expectant/nursing mothers, and young children—should follow the 2001 government guidelines designed to minimize mercury intake. And remember that those guidelines, which call albacore tuna relatively high in mercury, do not apply to our young, low-weight, minimal-mercury albacore!
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- Newswise/Medical News, July 19, 2005. IFT hears Americans not eating enough fish for good health. Accessed online July 20, 2005 at http://www.newswise.com/articles/view/513221/
- What You Need to Know about Mercury in Fish and Shellfish: 2004 EPA and FDA Advice for: Women Who Might Become Pregnant, Women Who are Pregnant, Nursing Mothers, Young Children. Accessed online October 21, 2005 at http://www.epa.gov/waterscience/fishadvice/advice.html