Manganese
- Nutritionally Essential
The Benefits of Manganese
By: Dr. George Obikoya
Manganese is a mineral element that is nutritionally
essential. The derivation of its name from the Greek word for magic
remains appropriate because scientists are still working to understand
the diverse effects of manganese deficiency.
Manganese is an antioxidant nutrient that is important in the breakdown
of amino acids and the production of energy. It is necessary for
the metabolism of Vitamin B-1 and Vitamin E and it activates various
enzymes which are important for proper digestion & utilization
of foods.
Manganese is a catalyst in the breakdown of fats and cholesterol.
It helps nourish the nerves and brain, is necessary for normal skeletal
development, and helps to maintain sex hormone production and to
regulate blood sugar levels. Manganese plays an important role in
a number of physiologic processes as a constituent of some enzymes
and an activator of other enzymes.
Manganese superoxide dismutase (MnSOD) is the principal antioxidant
enzyme of mitochondria, the power house in our cells. Because mitochondria
consume over 90% of the oxygen used by cells, they are especially
vulnerable to oxidative stress. The superoxide radical is one of
the reactive oxygen species produced in mitochondria during ATP
synthesis. MnSOD catalyzes the conversion of superoxide radicals
to hydrogen peroxide, which can be reduced to water by other antioxidant
enzymes.
A number of manganese-activated enzymes play important roles in
the metabolism of carbohydrates, amino acids, and cholesterol. Pyruvate
carboxylase, a manganese-containing enzyme, and phosphoenolpyruvate
carboxykinase (PEPCK), a manganese-activated enzyme, play critical
roles in gluconeogenesis, the production of glucose from non-carbohydrate
precursors.
Arginase, another manganese-containing enzyme, is required by the
liver for the urea cycle, a process that detoxifies ammonia generated
during amino acid metabolism.
Manganese deficiency results in abnormal skeletal development in
a number of animal species. Manganese is the preferred cofactor
of enzymes called glycosyltransferases, which are required for the
synthesis of proteoglycans that are needed for the formation of
healthy cartilage and bone.
Wound healing is a complex process that requires increased production
of collagen. Manganese is required for the activation of prolidase,
an enzyme that functions to provide the amino acid, proline, for
collagen formation in human skin cells. A genetic disorder known
as prolidase deficiency results in abnormal wound healing among
other problems, and is characterized by abnormal manganese metabolism.
Glycosaminoglycan synthesis, which requires manganese-activated
glycosyltranserases, may also play an important role in wound healing.
Although the specific mechanisms for manganese absorption and transport
have not been determined, some evidence suggests that iron and manganese
can share common absorption and transport pathways. Absorption of
manganese from a meal is reduced as the meal's iron content is increased.
Iron supplementation (60 mg/day for 4 months) was associated with
decreased blood manganese levels and decreased MnSOD activity in
white blood cells, indicating a reduction in manganese nutritional
status. An individual's iron status can affect manganese bioavailability.
Intestinal absorption of manganese is increased during iron deficiency,
and increased iron stores (ferritin levels) are associated with
decreased manganese absorption. The finding that men generally absorb
less manganese than women may be related to the fact that men usually
have higher iron stores than women. Supplemental magnesium (200
mg/day) decreased manganese bioavailability slightly, either by
decreasing manganese absorption or by increasing its loss in healthy
adults.
In one set of studies, supplemental calcium (500 mg/day) resulted
in slightly lower manganese bioavailability in healthy adults. As
a source of calcium, milk had the least effect, while calcium carbonate
and calcium phosphate had the greatest effect. Several others studies
have found the effect of supplemental calcium on manganese metabolism
to be minimal.
Manganese deficiency has been observed in a number of animal species.
Signs of manganese deficiency include impaired growth, impaired
reproductive function, skeletal abnormalities, impaired glucose
tolerance, and altered carbohydrate and lipid metabolism.
In humans, demonstration of a manganese deficiency syndrome has
been less clear. A child on long-term total parenteral nutrition
(TPN) that lacked manganese developed bone demineralization and
impaired growth that were corrected by manganese supplementation.
Young men who were fed a low-manganese diet developed decreased
serum cholesterol levels and a transient skin rash. Blood calcium,
phosphorus, and alkaline phosphatase levels were also elevated,
which may indicate increased bone remodeling as a consequence of
insufficient dietary manganese.
Young women fed a manganese-poor diet developed mildly abnormal
glucose tolerance in response to an intravenous (IV) infusion of
glucose. The adequate intake (AI) for manganese (2.3 mg/day for
adult men and 1.8 mg/day for adult women) appears sufficient to
prevent deficiency in most individuals.
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References
Kies C. Bioavailability of manganese. In: Klimis-Tavantzis DL, ed.
Manganese in health and disease. Boca Raton: CRC Press, Inc; 1994:39-58.
Johnson PE, Lykken GI. Manganese and calcium absorption and balance
in young women fed diets with varying amounts of manganese and calcium.
J Trace Elem Exp Med. 1991;4:19-35.
Norose N, Terai M, Norose K. Manganese deficiency in a child with
very short bowel syndrome receiving long-term parenteral nutrition.
J Trace Elem Exp Med. 1992;5:100-101 (abstract).
Friedman BJ, Freeland-Graves JH, Bales CW, et al. Manganese balance
and clinical observations in young men fed a manganese-deficient
diet. J Nutr. 1987;117(1):133-143.
Shetlar MR, Shetlar CL. The role of manganese in wound healing.
In: Klimis-Tavantzis DL, ed. Manganese in health and disease. Boca
Raton: CRC Press, Inc.; 1994:145-157.
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