FDA advice on fish consumption

For Americans concerned about mercury levels in certain types of fish, guidelines by the Food and Drug Administration should prove reassuring.

FDA says eating a variety of fish - the normal pattern of consumption - does not put people at risk of mercury poisoning. It is when people follow fad diets, eating one type of food or one species of fish, that problems could arise.

Mercury, which is released into the environment by both natural and man-made processes, can undergo chemical changes that transform it into methyl mercury. According to the FDA, fish absorb methyl mercury from the water, and as they feed on aquatic organisms. Larger predator fish are exposed to higher levels.

FDA considers methyl mercury levels of 1 part per million or less to be acceptable. When levels in certain species or in particular waters rise higher than 1 ppm, the FDA issues a warning.

The agency currently recommends that pregnant women limit their consumption of shark and swordfish to no more than once a month. Recent guidelines suggest that other people eat no more than about 7 ounces a week of shark, swordfish, and large species of tuna. Other types of fish and shellfish are considered to have negligible mercury levels.