Manganese

Manganese is required by several important enzymes: manganese superoxide dismutase, the mitochondrial antioxidant enzyme; glycosyltransferases needed for cartilage and bone matrix; arginase in the urea cycle; and pyruvate carboxylase in gluconeogenesis. Despite that importance, supplementing it is almost never necessary. Whole grains, nuts, legumes, leafy greens and tea supply manganese generously, and true dietary deficiency in humans is so rare that it has mostly been produced experimentally. The clinically relevant direction is excess. Chronic manganese overexposure causes manganism, a parkinsonian syndrome with tremor, rigidity and psychiatric changes, classically described in welders and miners inhaling manganese fumes but also reported with contaminated drinking water and long-term parenteral nutrition. People with liver disease clear manganese poorly and accumulate it in the basal ganglia. Because it appears in many bone-health and multivitamin formulas alongside other minerals, unintentional stacking is easy. The sensible position is to get manganese from food, check that supplements are not delivering doses near the 11 mg upper limit, and treat isolated manganese products as unnecessary for nearly everyone.