Results of landmark study refute US seafood-consumption advisories and indicate that pregnant/nursing mothers need to eat more fish, not less
by Craig Weatherby
The striking results of new research add great weight to prior findings indicating that higher fish consumption by pregnant and nursing mothers benefits their children’s development.
Specifically, the children of mothers who ate more fish than is advised under US guidelines (12 oz per week) scored higher on tests of intelligence, social and verbal skills, and showed greater physical dexterity, compared with the children of mother who ate less fish than US guidelines allow.
|Fish oil versus fish|
Why should pregnant and nursing women have to balance the risks and rewards of fish, when they can get ample amounts of omega-3s safely from supplemental fish oil?
First, this study compared mothers’ fish intake—not omega-3 intake—with children’s developmental outcomes. And there may be other critical nutritional factors far more abundant in fish than in standard fish oils—notably vitamin D—that aid brain development.
Second, not all mothers have the resources or awareness needed to add fish oil to their diets. For both reasons, it makes more sense for mothers to replace some part of their dietary protein (e.g., meat, dairy, soy) with relatively low-mercury fish during pregnancy and nursing.
The new study by Dr. Hibbeln and his colleagues in the US and UK put the issue of fish and pregnancy in perspective, and may finally end overblown fears that could conceivably lead mothers to under-consume fish, and thereby put their babies at risk of suboptimal brain development.
The data they analyzed came from a study of almost 9,000 British families taking part in the “Children of the 90s” project at Britain’s University of Bristol, also known as the Avon Longitudinal Study of Parents and Children, or ALSPAC.
Dr. Hibbeln’s team compared the amount of fish eaten by pregnant mothers with the development and behavior of their offspring up to the age of eight, and came to two clear conclusions:
“…we recorded no evidence to lend support to the warnings of the US [fish-and-mercury] advisory that pregnant women should limit their seafood consumption.
“…children of mothers who ate small amounts of seafood were more likely to have suboptimum neuron-developmental outcomes than children of mothers who ate more seafood.”
The developmental outcomes, in detail
After adjusting for 28 different factors—such as social class, or whether the mother breastfed—Dr. Hibbeln’s team found significant differences in the children’s development, related to their mothers’ fish intake.
The children born to mothers who ate more seafood than current U.S. guidelines for pregnant/nursing womenallow (12 ounces per week) displayed three key benefits:
In contrast, the less fish mothers ate, the worse their children performed in these key areas. Compared with children of women who ate more fish than the U.S. guidelines advise, the children of mothers who ate no fish displayed several developmental disadvantages:
Scored higher on tests measuring fine motor, communication, and social skills.
Showed better social behaviors.
Less likely to have low verbal IQ scores at age six.
As Dr Hibbeln said: “We have found that when women had low levels of seafood consumption, the outcome is exactly the opposite of what was assumed by the United States Advisory.
- 28 percent more likely to have poor communication skills at 18 months.
- 35 percent more likely to have poor fine motor coordination at age three and a half.
- 44 percent more likely to display poor social behavior at age seven.
- 48 percent more likely to have a relatively low verbal IQ at age eight.
“Unfortunately, the advice appears to have had the unintended consequence of causing harm in a specific developmental domain
—where protection was intended.”
Dr. Hibbeln’s Newsweek interview: reading between the lines
Dr. Hibbeln made some key points in an interview with Newsweek magazine online (Springen K 2007). Their positions as US government employees constrain researchers like Dr. Hibbeln from being completely frank, but his opinions become clear:
Newsweek: You found that women needed to eat more than 12 ounces of seafood per week to see beneficial effects on their children's development. Isn't that a lot of fish?
Dr. Hibbeln: It depends on where you live. If you're in Iceland, that's lunch.
Newsweek: But for many American women, doesn't 12 ounces sound huge?
Dr. Hibbeln: That would be two or three fish meals a week.
Newsweek: What about taking omega-3 supplements instead of eating an actual fish?
Dr. Hibbeln: This study looks only at seafood. Now there is separate data from other studies that have fairly consistently and uniformly showed benefits when pregnant women take supplements.
Newsweek: Is the actual fish better than any supplements?
Dr. Hibbeln: It's likely to be better. [Note to readers: see our sidebar titled “Fish oil versus fish”]
Newsweek: How did the FDA and EPA get it so wrong?
Dr. Hibbeln: That's not really something that is part of this manuscript. I think it is best said that these data indicate that the toxic effects of mercury may have been overestimated in relationship to the nutritional benefits of seafood.
Newsweek: Will the FDA and EPA change their guidelines?
Dr. Hibbeln: We as scientists at the NIH aren't trying to get them to do anything.… We've assessed the advisory, and we've concluded that the advisory causes the harm it intended to prevent.
We can only hope that these agencies heed the import of Dr. Hibbeln’s new findings, which are supported fully by the best available research.
New review scrutinized data from singular UK study
The data analyzed in Dr. Hibbeln’s new paper came from a landmark epidemiological study called the Avon Longitudinal Study of Parents and Children, or ALSPAC.
ALSPAC was designed to assess the impact of diet and other key factors that might affect the development, health, or wellbeing of children during and after pregnancy.
The ALSPAC researchers recruited some 85 percent of all pregnant women living in Bristol, UK, and surrounding areas with expected delivery dates between April 1, 1991 and Dec 31, 1992. Of 14,541 pregnancies, 13,988 children survived for at least 12 months
The mothers were sent questionnaires four times during pregnancy and then at specific time points after the birth of their children, to obtain information about their diet, education, and social circumstances, and about the behavioral and developmental status of their babies at ages 6, 18, 30, 42, and 81 months.
The food intake questionnaire assessed the women’s seafood consumption 32 weeks (8 months) into their pregnancies.
A set of questions completed by the mothers at home was used to calculate developmental progress in four areas: gross motor, fine motor, communication, and social skills. To ensure the reliability of the mothers’ evaluations, psychiatrists examined a subset of the children and found that the mothers’ evaluations matched their own quite closely.
When the children were 6.75 years of age, their intelligence quotients (IQ) were measured using a standard test.
Significantly, the failure to find any negative outcomes in the children of the UK mothers who ate the most fish could not be attributed to low mercury content of their fish. In fact, the fish that British people consume contains, on average, more mercury than the fish Americans eat.
Fish-and-mercury advisories: the hidden role of coal
We have no stake in the ongoing fight over mercury in fish—with big tuna canners on one side and consumer and environmental groups on the other—because we only sell fish whose size or diet preclude accumulation of relatively high levels of the problematic metal.
Our wild salmon, sablefish, scallops, and sardines are inherently low in mercury, and we offer only young, low-weight halibut and albacore tuna, which contain much less than bigger, older fish of the same species.
But we feel we must speak out against the unintended consequences of well-intentioned consumer-protection campaigns, which have cherry-picked evidence from deeply flawed, unreliable studies to pressure FDA and EPA to issue bad advice about seafood intake during pregnancy and nursing.
It’s a classic example of the law of unintended consequences: campaigns to limit mercury emissions from coal-burning power plants could harm millions of the kids they purport to protect.
We support the goal of reducing mercury emissions from coal-burning plants, since these do contaminate lakes and fresh water fish, and are clearly undesirable and unwarranted.
But the available science indicates that mercury emissions from coal-burning plants account for very little of the mercury in the ocean and ocean fish, most of which actually comes from seafloor geothermal vents.
In fact, the remains of fish that lived long before the industrial revolution show higher levels of mercury than their contemporary counterparts.
And when it came time to set “benchmark” safety levels for mercury intake in humans, the National Research Council (NRC) erred by dismissing the findings of the best study ever conducted.
Incredibly, the NRC rejected the results of the Seychelles Study (described below) because they showed no harm from copious fish consumption, and therefore didn’t fit with the findings of two other, scientifically inferior studies. (Even those studies detected only marginally significant evidence of developmental deficits.)
Therefore, the results of the Seychelles Study did not serve the Council’s need to find and quantify harm from mercury in fish, for use as the basis to set benchmark levels for mercury intake in humans. (See “Findings add seafood benefits”, below, and“Fight Over Mercury Risks”).
The NRC also erred in overlooking the ability of the selenium abundant in seafood to neutralize mercury (see “Mercury-Fighting Mineral in Fish Overlooked).
Findings add seafood benefits to safety assurances of Seychelles study
The “no harm” findings of the new study are supported by those of the well-designed but woefully under-publicized Seychelles Study, conducted in the small Indian Ocean island nation by medical researchers from New York’s University of Rochester.
The authors of that landmark investigation
—which is still ongoing
—examined the effects of maternal and child fish intake on brain development.
Compared with Americans, Seychelles islanders eat similar types of fish, containing similar amounts of omega-3s and mercury, but they eat far larger quantities of fish.
Nevertheless, the Seychelles study team found no negative effects of fish-eating among the 600-plus participating children—who are now about 16 years of age—even though they and their pregnant mothers ate many times more fish than the average American mother and child.
The authors of the only similar studies—conducted in New Zealand and the Faroe Islands (halfway between Iceland and Norway)—reported subtle developmental deficits when mothers and children ate large amounts of seafood.
But while these studies are often cited by anti-mercury campaigners, their findings were seriously flawed and unreliable, for the reasons explained in a previous issue of Vital Choices (see “Fight Over Mercury Risks”).
Dr. Hibbeln’s new report from Britain is especially relevant, since it involved people eating a standard Western diet and included nearly eight times as many women and children as participated in the Seychelles, Faroe Islands, or New Zealand studies.
- Hibbeln JR, Davis JM, Steer C, Emmett P, Rogers I, Williams C, Golding J. Maternal seafood consumption in pregnancy and neurodevelopmental outcomes in childhood (ALSPAC study): an observational cohort study. The Lancet 2007; 369:578-585.
- Daniels JL, Longnecker MP, Rowland AS, Golding J; ALSPAC Study Team. University of Bristol Institute of Child Health. Fish intake during pregnancy and early cognitive development of offspring. Epidemiology. 2004 Jul;15(4):394-402.
- Golding J, Pembrey M, Jones RALSPAC Study Team. ALSPAC: the Avon Longitudinal Study of Parents and Children. I. Study methodology. Paediatr Perinat Epidemiol 2001; 15: 74-87.
- ALSPAC Study Team. Accessed online at http://www.alspac.bris.ac.uk/welcome/index.shtml Feb 17, 2007.
- Springen K. Pregnant Women: Eat More Fish or Not? Newsweek. Accessed online Feb 17, 2007 at http://www.msnbc.msn.com/id/17177330/site/newsweek/