The Possible Essentiality of Inositol

There is no evidence that inositol is a dietary essential, because it is synthesized by aU eukaryotic cells. Infants may have a higher requirement than can be met by endogenous synthesis, and dietary inositol is a growth factor for the newborn mouse. In female gerbils, inositol is a dietary essential, and deficiency 

People with untreated diabetes have high plasma concentrations of free inositol, and high urinary excretion of inositol, associated with relatively low intracellular concentrations of inositol, suggesting that elevated plasma glucose may inhihit the uptake of inositol. There is some evidence that impaired nerve conduction velocity in diahetic neuropathy is associated with low intracellular concentrations of inositol and that inositol supplements improve nerve conduction velocity. However, high intracellular concentrations of inositol also impair nerve conduction velocity, and supplements may have a deleterious effect. 

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Figure 5.1 The structure of a glycerophospholipid. A simple diagram showing the charges on the head group. In this struction, palmitic and oleic acids, provide the hydrophobic component of the phospholipids and choline (and four bases) and the phosphate group provide the hydrophilic head. The unsaturated fatty acid, oleic acid, provides a kink in the structure and therefore some flexibility in the membrane structure which allows for fluidity. The more unsaturated the fatty acid, the larger is the kink and hence more fluidity in the membrane. Cholesterol molecules can fill the gaps left by the kink and hence reduce flexibility. Hydroxyl groups on the bases marked are those that form phosphoester links. Choline and inositol may sometimes be deficient in the diet so that they are, possibly, essential micronutrients (Chapter 15).

About 12 chemicals are widely recognised as vitamins (Table 15.3), although some are actually families of interconvertible chemical forms. Choline, inositol and bioflavonoids are considered to be possible vitamins. The essential fatty acids and essential amino acids are excluded... 

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