manganese

Manganese is an essential trace mineral naturally present in many foods and required by the human body in very small amounts to support multiple biochemical processes. It exists as the element Mn and as divalent ions (Mn2+) in the body. Unlike macrominerals like calcium or potassium, the total body store of manganese is only about 10–20 mg, with roughly 25–40% found in bone tissue and the remainder distributed to the liver, pancreas, kidneys, and brain. Manganese functions primarily as a cofactor for numerous enzymes, meaning it binds to and activates certain proteins required for catalyzing chemical reactions that sustain life. One of the best-known manganese-dependent enzymes is manganese superoxide dismutase (MnSOD), a mitochondrial antioxidant enzyme that converts superoxide radicals into less harmful molecules, thereby mitigating oxidative stress within cells. Mn also activates enzymes like pyruvate carboxylase (important in gluconeogenesis), arginase (amino acid metabolism), and glycosyltransferases (connective tissue synthesis). Because humans cannot synthesize manganese, dietary intake is necessary to maintain adequate tissue levels and prevent metabolic dysfunction. The mineral was recognized as essential in the early 20th century when studies demonstrated skeletal abnormalities in animals fed manganese-deficient diets. Today, manganese is widely acknowledged as a vital micronutrient for bone formation, enzyme function, and metabolic regulation.

Manganese plays multifaceted roles in human physiology, driven largely by its function as a cofactor for vital enzymes. One core role is in oxidative stress defense: manganese is a structural and catalytic component of manganese superoxide dismutase (MnSOD), a mitochondrial enzyme that neutralizes superoxide radicals generated during cellular respiration. By catalyzing the dismutation of superoxide into hydrogen peroxide and oxygen, MnSOD protects cells from reactive oxygen species (ROS) that can damage proteins, lipids, and DNA. In bone health, manganese supports the synthesis of glycosaminoglycans and proteoglycans essential for cartilage and bone matrix formation. Research published in the Journal of Clinical Medicine highlights manganese’s regulatory impact on osteoblast and osteoclast activity, influencing bone formation and resorption and contributing to bone mineral density and skeletal strength. Manganese also participates in carbohydrate metabolism by activating enzymes such as pyruvate carboxylase, which is critical for gluconeogenesis (generation of glucose from non-carbohydrate sources). This metabolic role indirectly supports blood sugar regulation. Evidence suggests that adequate manganese status may be associated with metabolic health markers; some cohort studies have found inverse associations between dietary manganese intake and type 2 diabetes incidence, though results are heterogeneous and gender differences may exist. Additionally, manganese is involved in amino acid and cholesterol metabolism, urea formation via arginase, and the synthesis of connective tissue components, thus contributing to wound healing and tissue integrity. In neurotransmitter synthesis, manganese contributes indirectly by supporting enzymes involved in precursor processing, which may affect brain function. Manganese-dependent enzymes are also implicated in immune function, reproductive health, and central nervous system health; however, clinical intervention evidence remains mixed, and benefits beyond preventing deficiency are not fully established.

Dietary recommendations for manganese are expressed as Adequate Intakes (AIs) because evidence was insufficient to establish an Estimated Average Requirement (EAR) and Recommended Dietary Allowance (RDA). For infants 0–12 months, the AI is 0.003 mg per day, while older children’s AIs gradually increase to about 1.9 mg per day for those aged 9–13 years. Teens and adults of both sexes typically have an AI of 2.2–2.3 mg per day. Pregnancy and lactation slightly modify these values to about 2.0–2.6 mg per day to account for additional metabolic demands. These values are based on typical intake levels associated with normal biochemical function and absence of deficiency. Several factors can influence manganese needs, including age, sex, genetic differences in absorption and transport proteins, liver function (critical for manganese excretion via bile), and dietary composition. Plant-based diets rich in whole grains, nuts, seeds, legumes, and tea often supply higher amounts of manganese, whereas diets low in these foods may provide marginal amounts. Because manganese competes with other divalent metals (e.g., iron, calcium) for absorption, high intakes of these minerals may reduce manganese absorption and slightly increase needs. While there is interest in potential optimal intake levels for metabolic health beyond the AI, robust evidence for this is lacking, and intakes above the tolerable upper limit (UL) are discouraged due to neurotoxicity risk.

True manganese deficiency is rare in free-living humans consuming diverse diets, in part because the mineral is ubiquitous in plant foods. Experimental deficiency studies have induced symptoms in controlled settings, but such severe restriction rarely occurs naturally. Indicators of deficiency include impaired bone growth and skeletal abnormalities such as weakened bone structure, poor cartilage formation, and increased fracture risk. Some clinical reports suggest associations between low manganese status and impaired glucose tolerance or metabolic irregularities, reflecting manganese’s role in carbohydrate metabolism. In animal studies, severe manganese restriction has led to dermatitis and altered lipid profiles, though human evidence is limited. Neurological symptoms such as mood changes, memory impairment, and coordination issues have been reported in contexts of low manganese levels, possibly due to its role in enzyme systems affecting neurotransmitter metabolism. Dermatologic signs including skin rashes and delayed wound healing may reflect disrupted connective tissue synthesis and antioxidant defense. Populations at risk include those with malabsorption disorders (e.g., celiac disease, Crohn’s disease), long-term parenteral nutrition without manganese supplementation, or genetic variants affecting manganese transport and homeostasis. Manganese blood testing is not routinely used in clinical practice due to variability and lack of well-defined deficiency thresholds; whole blood reference ranges are generally reported around 4–15 µg/L, though laboratory-specific values vary. Interpretation must consider clinical context, dietary intake, and potential exposure sources.

Manganese is most abundant in plant-based foods, particularly whole grains, nuts, seeds, legumes, spices, and some fruits. Whole grains such as brown rice and cooked oats are among the richest sources, with a cup of cooked brown rice providing substantial portions of the daily value and cooked oats similarly contributing high amounts due to intact bran layers. Nuts and seeds such as hazelnuts, pecans, macadamia nuts, and sunflower seeds supply significant manganese per ounce serving, often exceeding 40% of the daily value. Legumes including chickpeas, black-eyed peas, and edamame supply both manganese and plant protein, making them nutrient-dense choices. Spices like cloves and ground cinnamon are extremely concentrated sources; even small amounts can meaningfully contribute to manganese intake. Fruits such as pineapple, blackberries, raspberries, and blueberries contain moderate manganese levels, making them excellent additions to meals. Other sources include whole grain flours (e.g., rye), teff, and cooked millet, which are especially high in manganese when minimally processed. Plant-based milk alternatives and teas (especially black tea) also contribute manganese due to extraction during brewing. Because manganese is bound to plant matrices, bioavailability may be influenced by dietary factors such as phytate content; soaking, fermenting, or sprouting grains and legumes can enhance mineral absorption. Animal-derived foods generally have lower manganese content, though some shellfish (e.g., clams, mussels) contain measurable amounts. Overall, a varied diet rich in whole plant foods easily meets manganese needs without added supplements.

Manganese absorption occurs primarily in the small intestine through active transport and passive diffusion processes. Efficiency of absorption is relatively low (often 3–10%), meaning that only a fraction of dietary manganese is absorbed into circulation. Absorption competes with other divalent metals such as iron, calcium, copper, and zinc, which share transporters and can reduce manganese uptake when present in high amounts. Dietary components such as phytates and oxalates found in whole grains and leafy greens can bind manganese and inhibit absorption, whereas factors like vitamin C may modestly influence bioavailability. Once absorbed, manganese binds to plasma proteins (e.g., transferrin, albumin) and is transported to tissues for incorporation into enzymes and storage, with significant portions localizing in bone and the liver. The liver plays a central role in manganese homeostasis by excreting excess mineral into bile; impaired bile production or cholestasis can reduce excretion and predispose to accumulation. Blood manganese levels vary widely among individuals and are not routinely used to assess status due to poor correlation with tissue stores. Genetic factors affecting transporters (e.g., SLC39A8) can also alter manganese absorption and distribution, occasionally leading to clinical manifestations.

Most individuals can meet manganese needs through diet, as whole grains, nuts, legumes, seeds, and tea frequently supply adequate amounts. Supplements may be considered in cases of malabsorption disorders, parenteral nutrition without trace mineral coverage, or dietary restrictions that severely limit manganese-rich foods. Typical supplemental forms include manganese gluconate, manganese sulfate, manganese citrate, and chelated forms such as manganese bisglycinate. Chelated forms are designed to improve tolerability and may reduce interactions with inhibitors in the gut, although clear evidence of superior absorption is limited. Doses in supplements often range from 1–4 mg of elemental manganese per day; higher doses should be approached cautiously due to the narrow safety margin. Because manganese competes with other minerals for absorption, timing supplementation away from high-dose iron, calcium, or magnesium may enhance uptake. Signs of benefit are often subtle; clinicians may recommend supplements only when dietary intake is insufficient or in specific medical scenarios. Routine supplementation in healthy adults without deficiency signs is generally unnecessary and may increase risk of toxicity.

While manganese from a balanced diet rarely causes toxicity, excessive intake—particularly from supplements or environmental exposure (e.g., contaminated water or occupational inhalation of manganese dust)—can accumulate in the body and produce adverse neurological effects. The Tolerable Upper Intake Level (UL) for adults is established at 11 mg per day; exceeding this amount chronically may increase risk of adverse outcomes. Manganese toxicity primarily affects the central nervous system, manifesting with symptoms reminiscent of Parkinsonism including tremors, muscle spasms, difficulty with coordination, decreased balance, headaches, mood changes, and cognitive disturbances. Individuals with impaired liver function are at greater risk due to reduced biliary excretion, leading to higher systemic levels. Occupational exposure to manganese fumes or dust in welding and mining settings has long been recognized as a cause of “manganism,” a neurotoxic condition with motor and psychiatric symptoms. Environmental contamination of well water with high manganese levels has also been associated with neurological changes in some populations. Because blood manganese measurements do not reliably correlate with tissue burden, clinical diagnosis of toxicity relies heavily on exposure history and neurological assessment rather than isolated laboratory values.

Manganese interacts with certain medications due to its properties as a divalent cation. Manganese may form chelates with antibiotics such as quinolones (e.g., ciprofloxacin, levofloxacin) when taken concomitantly, potentially reducing antibiotic absorption and efficacy; studies examining in vitro interactions demonstrate complex formation with these drugs, particularly ciprofloxacin. Similarly, manganese may theoretically reduce the absorption of tetracycline antibiotics through interaction in the gastrointestinal tract, analogous to other multivalent cations that interfere with tetracycline absorption. Because of these interactions, guidelines for antibiotics like ciprofloxacin already advise spacing administration away from mineral-rich supplements or antacids that contain metal cations.

Common Forms: Manganese gluconate, Manganese sulfate, Manganese citrate, Manganese bisglycinate

Typical Doses: 1–4 mg elemental manganese per day in supplements

When to Take: Separate from high-dose minerals like iron or calcium

Best Form: Chelated forms (e.g., manganese bisglycinate) may improve tolerability

⚠️ Interactions: Quinolone antibiotics (e.g., ciprofloxacin) may form chelates, Tetracycline antibiotics may have reduced absorption