Being choosy at the fish counter could pay off in more ways than you might expect. In addition to leaving the oceans in better shape, choosing sustainably caught, contaminant-free fish could help you stave off diabetes, according to a new study in the journal Diabetes Care.
The researchers used data from an ongoing study investigating the health of 18- to 30-year-olds living in major metropolitan areas. The researchers tested the participants for levels of the heavy-metal mercury at the start of the study in 1987, and the participants were followed until 2005.
After 18 years, 288 of the original 3,875 study participants developed type 2 diabetes, and the researchers noticed a link between high levels of mercury at the start of the study and later development of the disease.
It's not clear why mercury and diabetes are linked, says lead researcher Ka He, MD, MPH, ScD, professor and chair of the department of epidemiology and biostatistics at Indiana University's School of Public Health. Lab studies have shown that mercury at levels similar to those found in some varieties of seafood damages pancreatic cells, and "that will affect insulin sensitivity or cause insulin resistance," Dr. He notes.
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This study simply found an association between the two, which can't prove cause and effect, but it does add to other evidence linking the toxic heavy metal to diabetes. Three studies done in Japan, Mexico, and Turkey have found that diabetics have higher levels of mercury (as detected in people's hair) than healthy people in the same age groups.
The relationship seems to be heavily dependent on diet, though. In Dr. He's study, when the researchers factored in the levels of omega-3 fatty acids, magnesium, and selenium in people's bodies, the chance that someone with high mercury levels would develop diabetes dropped significantly. That indicates, says He, that "some other nutrients in fish may attenuate or mask the adverse effect of mercury exposure."
It's never a good idea to load up on mercury. After all, the heavy metal is known to cause brain damage in children, and recent research has found that it causes inflammation, which can predispose you to heart disease, high blood pressure, and other heart problems.
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Protect yourself from all that—and from diabetes—by steering clear of these high-mercury bad actors, which were found in a 2010 study by the Environmental Defense Fund to have the highest mercury levels:
• King mackerel
• Tilefish from the Gulf of Mexico
• All varieties of tuna, with the exception of albacore tuna from the U.S. and Canadian Pacific coasts
• Most varieties of wild freshwater fish. A recent EPA analysis of U.S. rivers and streams uncovered that nearly every stream in the U.S. is home to fish with detectable levels of mercury. Check advisories from your local fish and wildlife service or department of conservation before you dive into a locally caught fish dinner.
A good rule of thumb is to avoid any fish that eats other fish, since mercury bioaccumulates up the food chain. But as this study shows, getting lots of other healthful nutrients, such as omega-3 fatty acids and magnesium, can counteract some of mercury's damage. Load up on omega-3s with wild-caught Alaskan salmon and get your magnesium from these sources:
• Garbanzo beans (or chickpeas)
• Almonds and cashews
• Homemade "bone broth" (a meat stock that's been boiled for 12 hours or more to get the most nutrition out of the bones)
• Blackstrap molasses.
Published on: April 8, 2013
Updated on: April 9, 2013