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Manganese

Manganese is an essential cofactor, but dietary deficiency in humans has essentially never been documented outside experimental depletion — while manganese excess is a well-characterised neurotoxic syndrome. This is a nutrient almost nobody should be supplementing.

What the science says

  • Deficiency is a non-problem; toxicity is the real one Moderate evidence

    Manganese is required for mitochondrial superoxide dismutase, arginase and several glycosyltransferases, but human dietary deficiency has never been convincingly demonstrated outside controlled depletion experiments — grains, nuts, tea and legumes supply it abundantly. The clinical literature on manganese is overwhelmingly about excess, and the same transport biology that makes it essential is what makes it neurotoxic above a threshold.

  • Excess causes manganism, a parkinsonian syndrome Moderate evidence

    Chronic overexposure — welding fume, contaminated drinking water, long-term parenteral nutrition, liver failure — accumulates manganese in the globus pallidus and produces manganism: dystonia, bradykinesia, gait disturbance, tremor and psychiatric change. It resembles Parkinson's disease but responds poorly to levodopa, and unlike most nutrient toxicities it is often only partially reversible after exposure stops.

  • Cognitive effects appear biphasic, not linear Limited evidence

    Reviews of manganese exposure across the lifespan describe an inverted-U dose-response, in which both unusually low and elevated exposures associate with poorer cognitive and motor performance, most consistently in children. The studies are observational with inconsistent exposure assessment, and no supplementation trial has demonstrated cognitive benefit at any dose in anyone.

Dosage & safety

Studied doseThere is no RDA — only an adequate intake of 2.3 mg/day for men and 1.8 mg/day for women, which normal diets exceed several times over. Tea, whole grains, nuts, legumes and leafy greens are dense sources; a few cups of tea alone can supply the AI. The tolerable upper limit is 11 mg/day for adults. Many multivitamins and "bone support" formulas contain 2-5 mg of manganese, which is unnecessary and stacks on top of a diet already providing plenty.
SafetyManganese is excreted almost entirely through bile, so anyone with cholestasis or cirrhosis loses their main clearance route and accumulates it — supplementation is contraindicated in liver disease. Neonates and patients on long-term parenteral nutrition are also at risk, which is why manganese has been reduced or removed from many PN formulations. Iron deficiency increases manganese absorption via shared DMT1 transport, so iron-deficient people take up disproportionately more from the same intake. Inhaled manganese (welding, mining) is regulated as an occupational hazard with exposure limits; oral supplements attract no comparable regulatory scrutiny despite there being no demonstrated benefit to offset the risk.

Scientific references

Where to buy

Solgar, Chelated Manganese, 100 Tablets (8 mg per Tablet)

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