Selenium containing antioxidant selenoproteins play an important role in the prevention and reversal of oxidative damage in the brain. This role has generally been underestimated in studies of the toxicity of elemental mercury and methylmercury. The common understanding has been that selenium helps to prevent mercury toxicity by binding with mercury and rendering the mercury inactive.
This chemical binding and inactivation of mercury does take place. Mercury has a great affinity for selenium, estimated to be approximately one million times stronger than mercury’s affinity for sulfur. So, selenium’s binding with mercury in the tissues does keep the mercury from getting into mischief in the brain and spinal cord, peripheral nervous system, and endocrine system.