Manganese is an essential trace element for humans and is required for normal amino acid, lipid, protein, and carbohydrate metabolism. It is present in virtually all diets at low concentrations. The average adult body contains between 12-20 mg, and most of it is in the bones, liver, kidney and heart. Mndependent enzyme families include oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Manganese metalloenzymes include arginase, glutamine synthetase, phosphoenolpyruvate decarboxylase, and Mn superoxide dismutase (MnSOD). Mn is involved in the function of numerous organ systems. It is needed for normal immune function, regulation of blood sugar and cellular energy, reproduction, digestion, bone growth, and it aids in defense mechanisms against free radicals. Mn in concert with vitamin K supports blood clotting and haemostasis.

Physiological role of manganese

Active in formation of amino acids, activates some enzymes, coenzyme activity. Manganese participates in many enzyme systems, although its role is not yet fully understood. It acts as a cofactor in enzymes that are essential for energy production and is involved in the metabolism of glucose, glycogen storage in the liver, protein digestion and synthesis of cholesterol and fatty acids. It is also essential for the synthesis of DNA and RNA molecules.

Manganese is a co-factor in phosphohydrolases and phosphotransferases involved in the synthesis of proteoglycans in cartilage. It is a part of enzymes involved in urea formation, pyruvate metabolism and the galactotransferase of connective tissue biosynthesis.

Mn activates several important enzyme systems and in this capacity it is required for the synthesis of acid mucopolysaccharides, such as chondroitin sulphate, to form the matrices of bones and egg shells. Consequently skeletal deformities and defects in shell quality occur when the manganese intake is inadequate.

Manganese is essential for the growth and maintenance of the nervous system, the development and maintenance of bones and joints, the function of female sex hormones and thyroid hormones.

Superoxide dismutase (SOD, MnSOD) is an antioxidant enzyme that in its structure contains manganese. When functioning proper, this enzyme provides protection against free radicals and the damage they cause in the body. In addition, this protein protects brain cells from damage that occurs in stroke and in Alzheimer disease. MnSOD protects the liver from damage. In alcoholics have shown a higher amount of MnSOD, which probably protects the body from oxidative damage caused by alcohol.

Metabolism

Only 3-5% of manganese is absorbed from food. After absorption manganese is transported to the liver. Manganese homeostasis is believed to be maintained by excretion of excess absorbed manganese through the gut, but the extent of endogenous gut losses of manganese has not been quantitated.

Manganese is excreted primarily in feces. Urinary excretion of manganese is low and has not been found to be sensitive to dietary manganese intake (Davis and Greger, 1992). Urinary excretion in a balance study of five healthy men varied from 0.04 to 0.14 percent of their intake, and absolute amounts in the urine decreased during the depletion phases of the study (Freeland-Graves et al., 1988).

Food sources of manganese

Good sources of manganese are cereals, spinach, bread made from whole-wheat flour, nuts, fruits, vegetables with dark green leaves (kale, broccoli), celery, chokeberry, figs, tea, liver, wheat bran, unpolished rice, almond, buckwheat, lentils, peas, carrots, raisins, prunes.

Recommended daily allowance

Manganese deficiency

Symptoms of manganese deficiency occur relatively infrequently and were first recorded in 1972. Lack of it usually occur if it is consumed large amounts of refined foods. Low intake of manganese increases the loss of calcium from bones and increases the likelihood of osteoporosis.

People with diabetes have low levels of manganese, which contributes to poor glucose regulation and reduced function of cells of the pancreas.

The lack of manganese plays an important role in epilepsy and infertility.

The lack of manganese leads to damage of the arteries, because the enzymes which in their structure contain manganese participate in the creation of arterial connective tissue. Damage to the arterial walls leading to binding of LDL cholesterol and atherosclerotic creating tiles.

Other symptoms of manganese deficiency are: Unconsciousness; Problems with bones; Slowed the growth of hair and nails; General body weakness; Hearing problems; Weight loss; Abnormal gait; Skin problems.

In children can also occur: Paralysis and Blindness.

Overdose

Toxic effects that occur with high intake of manganese are rare and include the appearance of lethargy, involuntary movements, changes in muscle tone and attitude, and in severe cases, coma. Toxic effect known as "manganese madness" was first observed in miners in the manganese mines. Symptoms include uncontrollable laughter, impulsivity, insomnia, violent behavior and hallucinations.

Manganese in medicine

Manganese supplements are used to treat inflammation, strains and sprains. Activity of the enzyme manganese superoxide dismutase is increased by adding of manganese and leads to better protection from oxidative damage that can occur in conditions such as arthritis.

Manganese is also used to treat schizophrenia, epilepsy, osteoporosis, multiple sclerosis, anemia and diabetes.

References

Chandra R.K., 1990, “Micronutrients and immune functions,” Annals of the New York Academy of Sciences; 587(1): 9-16. [Web Reference]

Davis C.D., Wolf T.L. and Greger J.L., 1992, “Varying levels of manganese and iron affect absorption and gut endogenous losses of manganese by rats,” The Journal of Nutrition; 122(6):1300-1308. [Web Reference]

Freeland-Graves J.H., et al., 1988, “Metabolic balance of manganese in young men consuming diets containing five levels of dietary manganese,” The Journal of Nutrition; 118(6): 764-773. [Web Reference]

Gordon R.F. and Jordan F.T.W., 1982, “Poultry diseases. 2^nd edition,” Bailliere Tindall, 1982.

Institute of Medicine (US) Panel on Micronutrients, 2001, “Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc,” Washington (DC): National Academies Press (US); 10, Manganese. [Web Reference]

Murray R.K., Granner D.K., Mayes P.A. and Rodwell V.W., 2000, “Harper’s Biochemistry, 25^th Edition,” McGraw-Hill, Health Profession Division, USA.

Soetan K.O., Olaiya C. O. and Oyewole O.E., 2010, “The importance of mineral elements for humans, domestic animals and plants-A review,” African Journal of Food Science; 4(5): 200-222. [Web Reference]