Manganese is an essential element in humans, with deficiency being characterised by nausea, growth retardation, skeletal abnormalities, decreases hair growth, impaired reproductive function, impaired glucose tolerance and low blood cholesterol concentrations. Manganese is essential because it is needed for the enzymes glucosyl transferase (transfers a sugar from uridine diphosphate to an acceptor), prolidase (hydrolyses dipeptides), arginase (urea formation), phosphoenolpyruvate carboxylase (converts oxaloacetate to phosphoenolpyruvate and carbon dioxide in gluconeogenesis), superoxide dismutase (prevents lipid peroxidation), pyruvate carboxylase (converts pyruvate to oxaloacetate); and may also bind to ATP and ADP to prevent cyclic AMP accumulation in cells. Manganese is only present is trace amounts in most human tissues with total body content for a typical male being around 10 to 20mg. Manganese is present in a wide variety of foods and generally the development of a deficiency is very difficult without the feeding of a diet devoid of manganese.
The effects of manganese have been investigated1 using 7 healthy male subjects (19 to 22 years). Individuals were fed a manganese adequate diet for 3 weeks, based an intake of ≈2.59mg/d manganese from food, after which subjects consumed a manganese deficient diet containing 0.11mg/d manganese for 39 days. The manganese deficient diets put the subjects in negative manganese balance but the plasma manganese concentration and hair manganese levels were not representative of manganese status. Faecal losses made up 99.5% of all losses, with depletion causing losses to drop to 86% by the end of depletion. In contrast urinary losses were never more than 0.6% and reached of 0.23% by the end of depletion. Level of plasma total cholesterol decreased significantly during depletion and never recovered in repletion. In addition, subjects reported itching with 70% developing scaly skin and rashes mainly on the upper torso.
During the repletion phase of the study, subjects took a manganese supplement containing either 1.39 or 2.39mg of manganese chloride, which reversed the dermatitis in all affected subjects. By the end of the repletion phase urinary losses of manganese had dropped to 0.26% and faecal losses had risen to 98%.These results show that depletion of manganese in healthy males manifests itself initially as the development of a dermatitis that is reversed upon adequate manganese being incorporated into the diet. The minimum requirements for males, based on this study was estimated by the authors to be 0.74 mg/d or 10.8 µg/kg, with individual requirements varying greatly (from 0.10 to 1.04 mg/d). Based on the losses from the lowest retention percentage and on a 12% retention of dietary manganese from other research, this figure rises to an intake of 2.5mg.d for a normal diet.
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