Greater exposure of mercury in young adults led to a 65 percent increased risk of developing type 2 diabetes later in life, a new study finds.
Most mercury exposure comes from eating fish and shellfish, nearly all of which contain traces of the element - but also lean protein and nutrients such as magnesium and omega-3 polyunsaturated fatty acids, otherwise part of your "complete breakfast."
In fact, the good and bad associations of fish and shellfish consumption are mirrored in the health indices of subjects in the study, reported today in the journal Diabetes Care. Once considered a poor man's meal, fish consumption is now a marker in Western countries for higher socioeconomic status - and the healthier lifestyles attendant with such status. Study participants who ate more fish also reported lower body mass indexes, smaller waistline circumferences and more exercise than others.
Researchers led by Indiana University School of Public Health at Bloomington followed 3,875 men and women, controlling for lifestyle and dietary consumption of magnesium and mega-3 polyunsaturated fatty acids, which researchers say might counter the effect of mercury. The findings suggest that choosing to eat fish and crustaceans lower in mercury might help people gain associated health benefits while avoiding disease risk, according to Ka He, an epidemiologist who led the study.
Salmon, shrimp and catfish have lower levels of mercury, compared to swordfish and shark, for example. Present in minute concentrations in seawater as a pollutant, mercury - usually in the form of methylmercury - is absorbed by algae which in turn is consumed by fish and shellfish, which absorb and mostly retain the bio-contaminant, excreting it slowly.
"It is likely that the overall health impact of fish consumption may reflect the interactions of nutrients and contaminants in fish," He said. "Thus, studying any of these nutrients and contaminants such as mercury should consider confounding from other components in fish."
He and his colleagues said the association between mercury exposure and diabetes was substantially increased even after controlling for the benefits of fish consumption, including magnesium and omega-3 polyunsaturated fatty acids.
The U.S. Environmental Protection Agency warns pregnant women in particular to limit fish consumption.