Manganese metal was isolated by Johann Gahn in 1774. He reduced the dioxide (MnO₂, as the mineral pyrolusite) with charcoal (essentially carbon) by heating and the result was a sample of the metal manganese. The origin of name "Manganese" is from the Latin word "magnes" meaning "magnet", or "magnesia nigri" meaning "black magnesia" (MnO₂).

The metal is gray-white, resembling iron, but is harder and very brittle. The metal is reactive chemically, and decomposes cold water slowly. Manganese is widely distributed throughout the animal kingdom. It is an important trace element and may be essential for utilisation of vitamin B. Manganese is present in quantity on the floor of oceans. It is an important component of steel.

Manganese, little known and underrated by both doctors and the general public, is an essential mineral important to many enzyme systems in carrying out such functions as energy production, protein metabolism, and bone formation, and the synthesis of L-dopamine, cholesterol, and mucopolysaccharides.

Manganese enables the body to utilize vitamin C, B1, biotin as well as choline. It is used in the manufacture of fat, sex hormones and breast milk in females. It is thought to also help neutralize free radicals as well as being of assistance in preventing diabetes and needed for normal nerve function. Manganese is also indicated in stimulating growth of the connective tissue and is also thought to be of importance in brain functioning.

In the food chain, most manganese is present in plant tissues, mainly in nuts, seeds, and whole grains, but in most vegetables as well, particularly the dark leafy greens. Like that of iron, our absorption of manganese is low; utilization of manganese from the diet has been estimated in the range of 15 — 30 percent efficiency.

Deficiencies are rare but would include poor bone growth, problems with the disks between the vertebrae, birth defects, convulsions, deafness, growth retardation, paralysis, reproductive difficulty and problems with blood glucose levels. Serious deficiency in children can result in paralysis, deafness and blindness. Manganese is not easily absorbed but since small amounts are needed deficiencies are not very general.

Whether manganese is useful in the treatment of diabetes by helping glucose metabolism or in people with osteoarthritis by stimulating mucopolysaccharide production to heal joints is still undemonstrated and questionable. It is more likely that a manganese deficiency reduces our ability to handle glucose and may thus worsen a diabetic condition. Manganese has also been tried in treatment for multiple sclerosis and myasthenia gravis. When given with B vitamins, manganese may alleviate fatigue or weakness by enhancing nerve impulses. Research has found most tumors and cancer cells to be very low in this mineral, which suggests a possibility that manganese may have a role in preventing cancer cell production and protecting against cancer growth.

Manganese has been helpful in some cases of fatigue (possibly by enhancing certain enzymes), poor memory (by protecting brain tissue and helping oxygenation), and nervousness, irritability, or dizziness. In his book Mental and Elemental Nutrients, Carl Pfeiffer, M.D., suggests that manganese along with zinc will help decrease copper levels by both decreasing absorption and increasing urinary losses. He feels that copper in higher than normal amounts can cause psychological problems and even some forms of schizophrenia (see the earlier section on Copper). Also, by some unknown mechanism, manganese may help reduce some of the parkinsonian symptoms, such as muscle rigidity and twitching, secondary to phenothiazine drug use. Manganese supplementation may also help in some cases of epilepsy.

Manganese has been used as a therapeutic nutrient, but other than preventing problems of manganese deficiency, its influence on certain disease states seems only anecdotal to date; further research will provide us with more evidence. The superoxide dismutase enzymes, only one of which contains manganese (others utilize zinc or copper), have an anti-inflammatory effect in the body, and this function may be relevant to many of the possible uses suggested here.

Toxicity by diet is rare. Delusions, hallucinations, insomnia, depression, impotency, irritability, mental illness, motor difficulties, weakness are signs of toxicity. Symptoms of excessive intake are similar to Parkinson's disease and Wilson's disease. Miners who are exposed to high levels of manganese, which can also be inhaled, can end up with "manganese madness".

Manganese is lost in milling. Absorption is also negatively influenced in the presence of large amounts of calcium, phosphorous, zinc, cobalt and soy protein. Manganese is depleted in the soil by extensive use of chemical fertilizers or too much lime, and food grown in such soil will have a low manganese content.

A higher intake may be necessary when breast-feeding or when taking a calcium or phosphorous supplement.

Nuts and whole grains are the best sources of manganese. Most animal foods have low levels, though egg yolks are a decent source. Seeds, legumes (peas and beans), and leafy greens, especially spinach, are all good sources of manganese if there is manganese in the soil in which these plants are grown. Alfalfa is high, and black teas and coffee beans have some manganese.