Amply covered by the diet; supplementation is rarely needed.
Controlled crossover trial: diets with very little (0.8 mg/d) or a lot of manganese (20 mg/d) did not change neuropsychological or metabolic measures in healthy young women. No clear effect in the short term.
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Manganese is an essential trace mineral whose biological functions are carried out through its incorporation into several key enzymes: mitochondrial superoxide dismutase (Mn-SOD, mitochondrial antioxidant defense), arginase (urea cycle), enzymes of carbohydrate and amino acid metabolism, and glycosyltransferase (synthesis of cartilage and bone proteoglycans); its clinical importance as an isolated supplement is modest because nutritional needs are small and easily met with varied diets, but the specific indications in conditions with a demonstrated deficiency or in situations of increased demand are clinically relevant.
The richest food sources are whole grains (especially brown rice and oats), nuts (especially pine nuts, hazelnuts, and almonds), legumes, seeds, tea (which provides particularly concentrated amounts), and shellfish; typical Western diets provide adequate amounts (1.8-2.3 mg/day), and clinical manganese deficiency is very rare except in prolonged parenteral nutrition without adequate supply or in some specific malabsorption conditions.
Manganese is a necessary cofactor for the synthesis of proteoglycans essential to the bone and joint matrix; although severe dietary deficiency is rare, several studies suggest that suboptimal intake may contribute to bone weakness, especially in interaction with deficiencies of other bone minerals (calcium, magnesium, vitamin K); in multimodal strategies for bone health, manganese in adequate nutritional amounts has a place as a component, not as the main intervention.
Mn-SOD is one of the main endogenous mitochondrial antioxidants, essential for neutralizing the superoxide generated during cellular respiration; adequate manganese intake is necessary to maintain this protective function, although supplementation at high doses provides no additional benefit in people with normal dietary intake.
Nutritional doses are 1.8-2.3 mg/day in adults; typical multivitamins contain 1-5 mg of manganese; the tolerable upper limit is 11 mg/day in adults; manganese-only supplements without a demonstrated deficiency are not usually necessary.
The most important safety consideration is neurotoxicity from chronic excess: manganism, a neurological condition that mimics Parkinson's disease, is documented in occupational exposure (miners, welders) and, exceptionally, in people on parenteral nutrition containing manganese or those who drink excessive amounts of water high in manganese; these situations are rare but illustrate the mineral's limited therapeutic margin; people with chronic liver disease should use caution because reduced biliary excretion may increase accumulation; those taking levodopa for Parkinson's should not specifically supplement; in pregnancy and breastfeeding, dietary intakes are safe and sufficient; manganese-specific supplements are rarely necessary for people with a normal varied diet.
Information, not medical advice. Scientific evidence reflects the quality of the studies.