Manganese
Manganese is a cofactor for manganese superoxide dismutase (MnSOD, a mitochondrial antioxidant), pyruvate carboxylase, and glutamine synthetase. Deficiency in humans is essentially unknown; toxicity, on the other hand, is a real occupational and environmental problem — chronic overexposure produces a Parkinson-like disorder called manganism.
Daily Adequate Intake
- Adult men: 2.3 mg/day.
- Adult women: 1.8 mg/day.
- Pregnancy: 2.0 mg/day.
- Lactation: 2.6 mg/day.
- Tolerable Upper Intake Level: 11 mg/day for adults from food and supplements combined.
Toxicity — manganism
Chronic inhalational or ingestion overexposure causes manganese accumulation in the basal ganglia, producing a Parkinson-like syndrome — bradykinesia, rigidity, gait disturbance, dystonic postures, and psychiatric changes. Historically an occupational disease of miners and steel welders; today the main risk groups are:
- Welders with long-term inhalation of welding fumes.
- Chronic liver disease — manganese is excreted in bile; hepatic failure causes accumulation.
- Total parenteral nutrition — IV manganese bypasses homeostasis; TPN patients need careful monitoring.
- Well-water consumers in some regions where groundwater manganese exceeds 300 µg/L; associated with impaired cognition in children.
- Ephedrone/methcathinone users (drug production uses potassium permanganate; contamination is severe).
The bone-formation claim
Manganese is a cofactor for glycosyltransferases involved in bone matrix formation. Some "bone health" supplements combine manganese with calcium and vitamin D. There is no evidence that manganese supplementation above dietary intake improves bone mineral density in humans with normal manganese status.
Food sources
- Mussels (3 oz): 5.8 mg — extreme outlier
- Hazelnuts (1 oz): 1.6 mg
- Pecans (1 oz): 1.3 mg
- Brown rice (1 cup cooked): 1.1 mg
- Oatmeal (1 cup cooked): 1.4 mg
- Whole wheat bread (1 slice): 0.5 mg
- Pineapple (½ cup): 0.8 mg
- Tea (1 cup): 0.4–0.5 mg — chronic heavy tea intake can contribute significantly