Manganese

What Is Manganese?

Manganese is an essential trace mineral that serves as both a structural component and a cofactor for numerous enzymes. The adult body contains approximately 10-20 mg of manganese, concentrated primarily in the bones, liver, pancreas, and kidneys. Manganese homeostasis is regulated primarily through biliary excretion rather than intestinal absorption, making the liver central to its metabolism.

Key Functions

• Antioxidant defense: Manganese superoxide dismutase (MnSOD), located in the mitochondrial matrix, is the primary antioxidant enzyme protecting mitochondria from superoxide radicals generated during aerobic metabolism. MnSOD is considered one of the most important antioxidant enzymes in the body.
• Carbohydrate metabolism: Pyruvate carboxylase, a manganese metalloenzyme, converts pyruvate to oxaloacetate — a critical step in gluconeogenesis and the replenishment of TCA cycle intermediates.
• Bone formation: Manganese is required for the synthesis of glycosaminoglycans (GAGs), structural components of cartilage and bone matrix. Enzymes involved in GAG synthesis — including glycosyltransferases — require manganese.
• Amino acid metabolism: Arginase, the final enzyme in the urea cycle, requires manganese to convert arginine to urea and ornithine.
• Wound healing: Manganese participates in collagen synthesis via its role in proline hydroxylation.

Dietary Reference Values and Food Sources

The Adequate Intake (AI) for manganese is 2.3 mg/day for men and 1.8 mg/day for women. The UL is 11 mg/day from all sources. Manganese is found mainly in plant foods:

• Cooked mussels (3 oz): ~5.8 mg
• Hazelnuts (1 oz): ~1.7 mg
• Brown rice, cooked (1 cup): ~1.8 mg
• Pineapple, raw (1 cup): ~1.5 mg
• Cooked spinach (1 cup): ~0.8 mg
• Oatmeal, cooked (1 cup): ~1.4 mg
• Black tea (1 cup): ~0.5 mg

Deficiency and Toxicity

Manganese deficiency is rare in humans eating varied diets. When experimentally induced, it causes bone abnormalities, impaired growth, reproductive dysfunction, altered carbohydrate and fat metabolism, and skin rash. Manganese toxicity — called manganism — occurs primarily through environmental or occupational inhalation of manganese-containing dust (mining, welding) rather than dietary intake. It causes neurological symptoms resembling Parkinson's disease: tremor, rigidity, bradykinesia, and psychiatric disturbances. The brain is particularly vulnerable because manganese accumulates in the basal ganglia.