Study Links Consumption of Fish, Seafood High in Mercury to ALS Risk

Margarida Azevedo, MSc avatar

by Margarida Azevedo, MSc |

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People who eat fish and seafood containing high concentrations of mercury may be more likely to develop amyotrophic lateral sclerosis (ALS), a new preliminary study suggests.

Researchers will present their study’s findings at the American Academy of Neurology’s 69th Annual Meeting, set for April 22-28 in Boston.

The question isn’t whether people should eat fish, the study’s author, Elijah Stommel, MD, PhD, of Dartmouth College in Hanover, New Hampshire, said in a press release. “For most people, eating fish is part of a healthy diet. But questions remain about the possible impact of mercury in fish.”

Currently, the U.S. Food and Drug Administration (FDA) recommends that women of childbearing age, pregnant women and children eat fish like salmon or sardines two to three times a week, because of their low concentration of mercury and high nutritional value (like omega-3 fatty acid content).

The FDA, on the contrary, recommends against consuming shark or swordfish, which are known to have two of the highest levels of concentration of mercury.

By measuring toenail clippings, researchers found that, of the 518 people studied (294 with ALS, and 224 without), about 179 people, or 61 percent, with ALS were in the top 25 percent for estimated mercury intake, compared to only about 98 people, or 44 percent, who did not have ALS.

The researchers estimated annual exposure to mercury by looking at average mercury levels in the types of fish, and how often participants reported eating them. They asked people how much fish and seafood they ate on a regular basis and what types of fish and what stores they bought it from, or where they caught it.

The study also found that among regular consumers of fish and seafood, those in the top 25 percent for estimated annual mercury intake had twice the risk of developing ALS than those in the lower percentiles.

The causes of ALS are still unknown. However, some previous studies have suggested that mercury could be a significant risk factor for the development of neurodegenerative disorders like ALS, as it is a known neurotoxic metal. In the United States, the primary source of exposure to mercury is through eating contaminated fish.