Scientists from Dartmouth College in Hanover, N.H. will present the findings of a study at the American Academy of Neurology’s Annual Meeting in April that links eating fish and seafood with higher levels of mercury to amyotrophic lateral sclerosis (ALS) also known as Lou Gehrig’s disease. Mercury is a neurotoxic metal and the primary source of exposure for people in the United States is via consumption of methylmercury-contaminated fish. The preliminary study published by the AAN suggests that while ALS does not have a known cause, mercury could be a risk factor for the disease.
The scientists completed a survey of 518 people, including 294 who had ALS and 224 who did not, asking about their fish and seafood consumption.
Annual exposure to mercury for the survey subjects was estimated by considering the average mercury levels of the fish most frequently consumed and how often fish and seafood was eaten. Fish such as swordfish and shark typically have high levels of mercury while salmon and sardines have low mercury yet are high in beneficial omega-3 fatty acids. In addition to estimating the exposure to mercury, scientists also measured the levels of mercury in the participants by taking samples of toenails.
“The study found that among participants who ate fish and seafood regularly, those in the top 25 percent for estimated annual mercury intake were at double the risk for ALS compared to those with lower levels. A total of 61 percent of people with ALS were in the top 25 percent of estimated mercury intake, compared to 44 percent of people who did not have ALS. They also found that higher mercury levels measured in toenail clippings were associated with an increased risk of ALS. Those in the top 25 percent of mercury levels, based on fish-related intake or toenail clippings, were at a two-fold higher risk of ALS. These findings need to be replicated in additional studies.”
Eating fish has many health benefits, but the study does recommend that consumers should be more selective about the fish and seafood they eat, selecting “species that are known to have a lower mercury content, and avoid consuming fish caught in waters where mercury contamination is well-recognized.”
Scientists concluded, “the data demonstrate that the risk of ALS is associated with fish and seafood consumption. Both estimated fish-related mercury intake and biomarker data suggest mercury exposure is a risk factor for ALS.” They also suggest that additional research is recommended before fish-consumption guidelines for neurodegenerative diseases can be made.
ALS is a progressive neurological disease that attacks the nerve cells and their ability to interact with the body’s muscles. The disease ultimately results in complete paralysis of the body, and there currently is not a cure.
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