Mercury in Fish, Seafood May Be Linked to Higher ALS Risk

Eating fish and seafood with higher levels of mercury may be linked to a higher risk of amyotrophic lateral sclerosis (ALS), according to a preliminary study that will be presented at the American Academy of Neurology’s 69th Annual Meeting in Boston, April 22 to 28, 2017. However, fish and seafood consumption as a regular part of the diet wasn’t associated with ALS.

“For most people, eating fish is part of a healthy diet,” says study author Elijah Stommel, MD, PhD, of Dartmouth College in Hanover, New Hampshire, and a Fellow of the American Academy of Neurology. “But questions remain about the possible impact of mercury in fish.”

While the exact cause of ALS is unknown, some previous studies have suggested mercury to be a risk factor for the disease. In the United States, the primary source of exposure to mercury is through eating fish contaminated with the neurotoxic metal.

Often referred to as Lou Gehrig’s disease, ALS is a progressive neurological disease that takes away the ability of nerve cells to interact with the body’s muscles. Early symptoms of the disease can include muscle twitching and weakness in a limb. It typically develops into complete paralysis of the body, including the muscles needed to speak, eat, and breathe. There is no cure for ALS, and eventually the disease is fatal.

For the study, researchers surveyed 518 people, 294 of whom had ALS and 224 of whom didn’t, on how much fish and seafood they ate. Participants reported the types of fish they ate, and whether they were purchased from stores or caught when they were fishing.

Researchers estimated the annual exposure to mercury by looking up the average mercury levels in the types of fish and the frequency that the participants reported eating them. Swordfish and shark are examples of fish that are considered high in mercury, while salmon and sardines typically have lower levels. Researchers also measured the levels of mercury found in toenail samples from participants with ALS and compared those levels to people without ALS.

The study found that among participants who ate fish and seafood regularly, those in the top 25% for estimated annual mercury intake were at double the risk for ALS compared with those with lower levels. A total of 61% of people with ALS were in the top 25% of estimated mercury intake, compared with 44% of people who didn’t 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% 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.

The authors emphasize that this study doesn’t negate the fact that eating fish provides many health benefits. However, the study suggests that the public may want to choose species that are known to have lower mercury content and avoid consuming fish caught in waters where mercury contamination is well recognized. More research is needed before fish consumption guidelines for neurodegenerative illness can be made.

Currently, the FDA health recommendations for women of childbearing age and children are to eat two to three weekly meals of species such as salmon or sardines that have low mercury but are also high in nutrients such as potentially beneficial omega-3 fatty acids. The FDA recommends avoiding fish with the highest mercury levels, such as shark and swordfish. Check for waterbody-specific fish advisories when consuming fish caught by family or friends.

Source: American Academy of Neurology

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Does Mercury in Fish Play a Role in Lou Gehrig’s Disease (ALS)?

Eating mercury-laden seafood may raise the risk of developing ALS (Amyotrophic Lateral Sclerosis), preliminary research suggests.

The report warns of possible harm from fish containing the most mercury, such as swordfish and shark. It doesn’t suggest a higher risk of ALS from general consumption of seafood.

“For most people, eating fish is part of a healthy diet,” said study author Dr. Elijah Stommel, who’s with Dartmouth College’s Geisel School of Medicine in Hanover, N.H.

“But questions remain about the possible impact of mercury in fish,” Stommel said in an American Academy of Neurology news release.

The study of 500-plus people found that seafood eaters who ate the most mercury-heavy fish may face double the risk of developing ALS.

However, the study only established a link between the two, not a cause-and-effect relationship.

Mercury is a toxic metal that occurs naturally in the environment. It tends to be lower in fish such as salmon and sardines, and the study authors stressed that seafood confers many health benefits. But they suggested paying attention to what type of seafood you eat.

ALS, an incurable neurodegenerative disease, is also called Lou Gehrig’s disease in memory of the legendary baseball player who died from it. It often starts with muscle weakness or twitching and eventually develops into complete paralysis and death.

In the United States, just over 6,000 people are diagnosed with ALS each year, according to the ALS Association.

What causes ALS is unknown, but some research has identified mercury as a risk factor. Americans most commonly encounter mercury when they eat fish that contains it, the researchers pointed out.

For the study, the researchers surveyed 294 people with ALS and 224 without it.

Participants were asked about their seafood consumption and whether they caught it themselves or bought it. The researchers then estimated how much mercury the participants consumed annually. They also tested participants’ toenail clippings for mercury content.

The results: 61 percent of those with ALS were in the top quarter of mercury consumption, compared to 44 percent of those without ALS.

Among regular seafood eaters, people in the top quarter of mercury consumption were at twice the risk of ALS, the researchers determined. People with the highest mercury levels, based on toenail clippings and diet, also had twice the risk, they said.

The U.S. Food and Drug Administration suggests that children and women of childbearing age eat two to three meals a week of fish like salmon, cod and sardines that are high in nutrients and lower in mercury. The FDA recommends against fish like shark, marlin and swordfish because of their higher mercury content.

The study results are scheduled for release at the American Academy of Neurology’s annual meeting April 22-28, in Boston. Research presented at conferences should be considered preliminary until published in peer-reviewed medical journals.

Source: HealthDay


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Eating Bright-Colored Fruits and Vegetables May Prevent or Delay ALS

New research suggests that increased consumption of foods containing colorful carotenoids, particularly beta-carotene and lutein, may prevent or delay the onset of amyotrophic lateral sclerosis (ALS). The study, published by Wiley in Annals of Neurology, a journal of the American Neurological Association and Child Neurology Society, found that diets high in lycopene, beta-cryptoxanthin, and vitamin C did not reduce ALS risk.

Carotenoids give fruits and vegetables their bright orange, red, or yellow colors, and are a source of dietary vitamin A. Prior studies report that oxidative stress plays a role in the development of ALS. Further studies have shown that individuals with high intake of antioxidants, such as vitamin E, have a reduced ALS risk. Because vitamin C or carotenoids are also antioxidants, researchers examined their relation to ALS risk.

According to the National Institutes of Neurological Disorders and Stroke (NINDS) roughly 20,000 to 30,000 Americans have ALS—also known as Lou Gehrig’s disease—and another 5,000 patients are diagnosed annually with the disease. ALS is a progressive neurological disease that attacks nerve cells (neurons) in the brain and spinal cord, which control voluntary muscles. As the upper and lower motor neurons degenerate, the muscles they control gradually weaken and waste away, leading to paralysis.

“ALS is a devastating degenerative disease that generally develops between the ages of 40 and 70, and affects more men than women,” said senior author Dr. Alberto Ascherio, Professor of Epidemiology and Nutrition at Harvard School of Public Health in Boston, Mass. “Understanding the impact of food consumption on ALS development is important. Our study is one of the largest to date to examine the role of dietary antioxidants in preventing ALS.”

Using data from five prospective groups: the National Institutes of Health (NIH)–AARP Diet and Health Study, the Cancer Prevention Study II-Nutrition Cohort, the Multiethnic Cohort, the Health Professionals Follow-up Study, and the Nurses’ Health Study, researchers investigated more than one million participants for the present study. A total of 1093 ALS cases were identified after excluding subjects with unlikely food consumption.

The team found that a greater total carotenoid intake was linked to reduced risk of ALS. Individuals who consumed more carotenoids in their diets were more likely to exercise, have an advanced degree, have higher vitamin C consumption, and take vitamin C and E supplements. Furthermore, subjects with diets high in beta-carotene and lutein—found in dark green vegetables—had a lower risk ALS risk. Researchers did not find that lycopene, beta-cryptoxanthin, and vitamin C reduced the risk of ALS. Long-term vitamin C supplement intake was also not associated with lower ALS risk.

Dr. Ascherio concludes, “Our findings suggest that consuming carotenoid-rich foods may help prevent or delay the onset of ALS. Further food-based analyses are needed to examine the impact of dietary nutrients on ALS.”

Source: Wiley