From Environmental Health News:

A study raises concern about children’s exposure to mercury through fish eating, tying it for the first time to hormone changes that increase chronic stress and associated immune system dysfunction.

The mercury levels measured in the children were well below the levels considered a health risk by the U.S. Environmental Protection Agency.

This new study from Oswego County, New York, finds that higher mercury levels measured in the children’s blood are significantly associated with lower cortisol levels. The hormone cortisol is released in response to stress and is important for metabolism, immune responses and blood pressure. Its levels naturally fluctuate during the day – levels are higher in the morning and lower in the afternoon.

Even lower cortisol levels and responses can result in chronic stress even though stress increases the hormone’s level. The study’s results suggest that mercury exposure at levels commonly seen in fish eating populations may do this. It may act as a chronic stressor and disrupt the stress response. Chronic stress means the body doesn’t relax – cells continually function in high gear and do not return to a normal state. Long-term stress can have many negative health effects such as increased heart disease, more metabolic disorders and lowered immunity.

The findings are in line with prior studies in people and fish. The toxic metal increased inflammation in miners exposed to mercury. Animal studies find reduced cortisol levels in mercury-contaminated fish after capture stress.

Fish consumption is a major source both of beneficial omega-3 fatty acids and toxic mercury. Omega-3s benefit health by protecting against heart disease. Mercury is potentially harmful because it affects the brain and nervous system in children. Although there are fish advisories in many states, it is still uncertain whether the benefit of eating fish outweighs the potential harm in children.

To address the pros and cons of fish eating in children, the researchers examined 100 children from 9 to 11 years old in New York State. Parents reported children’s fish consumption, which was categorized as eating or not in the analysis. Blood mercury levels, blood lipids, cortisol in saliva and inflammation markers were measured. Blood lipids indicate future heart disease risk; cortisol reflects changes of stress response; and inflammation markers indicate immune response differences.

Fish eaters had higher HDL – or so called good cholesterol – related to lower heart disease risk, than non-fish eaters. However, the fish eaters also had much higher – almost three times higher – mercury levels than non-fish eaters (1.1 and 0.4 microgram per liter, respectively).

More.

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