Vitamin B8 ( inositol )

Inositol is another B complex factor with nebulous status. Animal experiments have identified it as a necessary factor for growth and survival, but there has been little human research on specific deficiency symptoms. Inositol is concentrated in the skeletal and heart muscles, lungs, liver, brain, blood, milk, urine, and eggs. Its metabolic role in these and other tissues is not yet known.

Nonetheless, some research has indicated possible practical uses for inositol. Animal experiments have demonstrated that raising dietary inositol levels prevents the decrease in motor nerve conduction that results from degeneration of nerve insulation in diabetes. Inositol supplementation in the diets of human diabetics had a similar effect. The more inositol in the diet (maximum 1400 mg.), the better the nerve conduction. When the people ate an inositol-deficient diet, nerve conduction was lowest. An inositol-"adequate" diet improved nerve conduction over the deficient diet, but not as much as the supplemented diet.

Inositol has also been shown to be of possible use against some forms of cancer. Intravenous injections of inositol inhibited tumor growth in mice, in one experiment. The degree of inhibition increased with the amount of inositol used. One doctor tried high doses of inositol (three to four grams daily) in people with advanced cases of cancer of the genito-urinary tract. The seven cases with terminal malignancies of the prostate, penis, and testicle were not apparently benefited. But six cases of bladder cancer were helped. Their tumors reduced in size, and their hematuria (blood in the urine) disappeared.

Inositol has also been shown to increase the ability of the liver to resist fatty infiltration and damage by toxins. It has also been reported to lower cholesterol in man and animals. However, the source of the inositol was lecithin. Since lecithin also contains choline and other substances, the cholesterol-lowering effect may not have been due to inositol alone, even though the researchers did attribute the effect to inositol.

Where is it found ?

Sources of inositol include lecithin, yeast, organ meats, nuts, fruit, vegetables, and whole grains. Inositol supplements are available in a wide range of doses, from less than a hundred milligrams up to several hundred. The fact that both animals and people have been aided by supplements of inositol indicates that the body does not always synthesize an "adequate" amount.

Who is likely to be deficient ?

Clear deficiency of inositol has not been reported, although diabetics have increased excretion and may benefit from inositol supplementation.

How much to take

Most people do not need to take inositol. In addition, the small amounts commonly found in multi-vitamin supplements are probably unnecessary and ineffective. Nutritionally oriented doctors sometimes suggest 500 mg twice per day.

Side effects

Toxicity has not been reported, although people with chronic renal failure show elevated levels.
Large amounts of phytate, the common dietary form of inositol, reduce the absorption of calcium, iron, and zinc. However, supplemental inositol does not have this effect.

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