Nutrition versus toxicology of manganese in humans: Evaluation of potential biomarkers

Manganese intake can vary greatly with food choices, water composition, and supplement use. Thus, individuals consuming Western diets consume from <1 to >10 mg Mn/d. The levels of manganese intake associated with adverse effe cts (both deficient and toxic) are debatable. Moreover, many of the symptom s of manganese deficiency (growth retardation, changes in circulating HDL c holesterol and glucose levels, reproductive failure) and manganese toxicity (growth depression, anemia) are nonspecific. The bone deformities observed in manganese-deficient animals and neurological symptoms of individuals wh o have inhaled excess manganese are permanent and illustrate the need to id entify sensitive biomarkers of manganese status that appear before these sy mptoms. Manganese balance and excretion data are not useful biomarkers of m anganese exposure but demonstrate that the body is protected against mangan ese toxicity primarily by low absorption and/or rapid presystemic eliminati on of manganese by the liver. Serum manganese concentrations in combination with lymphocyte manganese-dependent superoxide dismutase (MnSOD) activity and perhaps blood arginase activity, appear to be the best ways to monitor ingestion of insufficient manganese. Serum manganese concentrations in comb ination with brain MRI (magnetic resonance imaging) scans, and perhaps a ba ttery of neurofunctional tests, appear to be the best ways to monitor exces sive exposure to manganese. (C) 1999 Inter Press, Inc.