Inositol

Description

Inositol is a cyclic 6-carbon compound found in nearly all plant and animal cells, suggesting it is an essential cell constituent. It is found both in free form and combined with other compounds. Inositol is found in the diet as a component of phospholipids and phytic acid (inositol hexaphosphate). It is converted in the brain and cerebrospinal fluid; it is also found in skeletal and heart muscles, and in the liver and kidneys. The level of inositol is very high in male reproductive organs, and particularly in semen.

Since humans can synthesize inositol, the need for it as a nutritional requirement has not been proven.

Method of Action

Inositol is present in cell membranes as phosphatidylinositol. Phosphatidylinositol is a phospholipid, a structural element of cell membranes. Inositol functions to mediate cell responses to stimuli, nerve transmissions and the regulation of enzyme activity. Inositol is also considered to have lipotrophic activity. It is believed to function in phospholipid synthesis and, therefore, to affect the function of lipid-transporting molecules.

Experiments have shown that inositol is a growth factor for a wide variety of human cell lines in tissue culture.

Large amounts of phytic acid (phosphorylated inositol) in the diet interferes with the absorption of calcium, iron and zinc; however, pure inositol favors the absorption of zinc. Vitamin B-Complex vitamins, choline, and linoleic acid assist the absorption of inositol from the intestines. Alcohol, coffee, and cola drinks containing caffeine, as well as tobacco, inhibit inositol absorption.

Properties & Uses

Inositol may have a therapeutic role in the treatment of diabetes. Experiments with diabetic rats revealed an impaired ability to maintain normal levels of inositol in the peripheral nerves, which was related to decreased motor nerve conduction velocity.

This condition was alleviated by inositol supplements. This is, however, experimental data; the use of inositol for diabetes is still under investigation.

Consequence of Deficiency

Inositol deficiency is uncommon because of its widespread availability in food. Animals with inositol deficiency produce an accumulation of triglycerides in the liver, intestinal disturbances of fat metabolism, and other abnormalities such as eye disorders, high cholesterol, skin problems, and constipation.

Toxicity Factors

No toxic effects have been reported related to inositol.

Recommended Dietary Allowance

The RDA for inositol has not been established, but a general guideline recommended by most authorities suggests consuming the equal amounts of inositol and choline.

The daily consumption of inositol in food is approximately one gram. One tablespoon of brewer's yeast provides 40 milligrams of choline and inositol.

Therapeutic doses range from 500 to 1,000 milligrams daily.

Food Sources

Beef liver	Fruits
Grains	Nuts
Legumes	Organ meats
Raw milk	Vegetables
Brewer's yeast

Abstracts

References

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