What about PCBs?
Fish, meat and dairy foods all contain polychlorinated biphenyls (PCBs), a man-made mixture of chlorinated compounds often used in the manufacture of plastics and for other commercial uses before 1977.
Although manufacturing of PCBs was banned in the U.S. that year because of evidence of harmful health effects, these fat-soluble compounds build up in the environment, are stored in the tissues of animals and humans and take many years to break down. Overexposure in women can lead to having a baby with low birth weight, as well as problems with motor skills, short-term memory and the immune system.
However, dietary overexposure is not usually a concern for the general population, says Harvard's Dariush Mozaffarian, M.D., DrPH, who has conducted research on the benefits of seafood. "PCB levels in commercially available ocean-caught fish are far lower than FDA-action levels and should have little impact on individual decisions regarding fish consumption," he says. (Since levels in freshwater fish can vary depending on local conditions, consult your area's advisories before eating fish from these waters.)
Other experts feel that PCB levels can be an issue, especially when it comes to farmed fish; research is ongoing to determine the appropriate level of concern.
The Perfect 10?
The most recent research shows that eating more than the recommended 12 ounces of seafood a week may confer greater benefits to babies. If you choose to eat this much, stick with the following 10 varieties (listed here in alphabetical order); they are high in omega-3s and low in mercury:
2. Atlantic herring
3. Atlantic mackerel (not king mackerel)