Manganese

Manganese is a trace mineral involved in bone formation, immune function, antioxidant activity, and carbohydrate metabolism. Although manganese deficiency is rare, deficiencies are associated with skeletal problems (undermineralized bone and increased risk of fracture) and poor wound healing. It appears that the greatest risk of deficiency is found in people on diets (inadequate intake) or where malabsorption occurs. Manganese is in competition with calcium, iron, and zinc for absorption, so an excess intake of these other minerals may decrease manganese absorption and lead to deficiency symptoms. Much like iron, manganese absorption is enhanced with vitamin C and meat intake. Food sources of manganese include coffee, tea, chocolate, whole grains, nuts, seeds, soybeans, dried beans (navy beans, lentils, split peas), liver, and fruits. As with several other minerals, the intake of foods high in oxalic acid (present in dark green leafy vegetables) may inhibit manganese absorption. The adult DRI for manganese is 2.3 milligrams per day for men and 1.8 milligrams per day for women. The safe upper limit is set at 11 milligrams per day for both men and women, with an excess intake causing neurological symptoms. As with copper, excessive intakes of calcium, phosphorus, iron, zinc, fiber, and oxalic acid all decrease manganese absorption.