Mercury blood levels in women of childbearing age have dropped by 34 percent, even though fish consumption has remained relatively constant over the past decade, a new government study shows.
Most likely that’s because women between the ages of 16 and 49 have been choosing fish that is low in mercury, researchers from the Environmental Protection Agency concluded.
“We were thrilled to have this finding,” said Betsy Southerland, director of the Office of Science and Technology for the EPA’s Office of Water.
Southerland and others suspect that women are heeding public service messages.
“In 2001, the EPA and the FDA jointly put out a national fish advisory to women of childbearing age, saying here’s what to avoid, but we still encourage you to eat fish because it’s really healthy,” Southerland said.
The EPA researchers scrutinized data from the National Health and Nutrition Examination Survey (NHANES), comparing blood mercury levels from the 1999-2000 survey to those from biennial follow-up surveys. It turns out that mercury levels in that first survey were 1.5 times higher than the subsequent ones.
The problem with mercury is that at higher levels it can harm developing nervous systems in unborn babies and young children, Southerland said. “It can lead to problems with thinking, memory and attention, as well as problems with fine motor skills and visual-spatial problems in children who were exposed in utero or shortly thereafter,” she added.
That’s why experts suggest women who are pregnant or might become pregnant steer clear of fish that contain higher mercury levels. That warning goes for women who are nursing, also.
“Mercury can cause problems even in adults,” Southerland said. But for adults to experience problems, levels need to be approximately 20 times those that cause harm to developing babies and children.
While nutritionists consider fish to be an important part of a healthy diet, nearly all fish contain some mercury. Among the fish that contain the highest levels of mercury are shark, swordfish, king mackerel and tilefish.
The EPA and FDA advise women to eat up to 12 ounces of fish per week, as long as they are varieties that contain low levels of mercury, such as shrimp, canned light tuna, salmon, pollock and catfish.
While the researchers can’t prove that women have cut back because of the government warnings, “we know from the data that mercury levels haven’t dropped in fish and women are still eating the same amounts of fish,” Southerland said. “So that must mean that they are eating fish with lower mercury concentrations.”
The new findings show that Americans are getting the message about mercury, said Anna Ardine, a clinical nutritionist at Magee-Womens Hospital of the University of Pittsburgh Medical Center.
“This is a good thing,” Ardine said. “I’ve been talking about this for the last 15 years to my patients.”
She sees the EPA's findings as part of a larger trend.
“I think there’s a heightened awareness about where our food is coming from,” Ardine said. “People are concerned not just that it is cheap and convenient, but also that it is wholesome.”