Inositol

Inositol is usually classified among the B complex vitamins, but is not strictly a vitamin - it is made fairly easily in two stages from glucose in the body. However, like a number of other biochemicals to which this applies, inositol is often made in inadequate amounts for optimum health, so supplementation with inositol can often improve health and help to reduce the severity of various health disorders.
Inositol is an important part of the structure of cell membranes, forming part of the structure of the phospholipids that are the main part of them, along with choline. Inositol also needs unsaturated (essential) fatty acids to go along with it, for the same reason.
Inositol is particularly important in the structure of the membranes of the nervous system, particularly the brain. Inositol is therefore useful for various nervous system disorders, including depression, hyperactivity and nervousness.
Inositol can also be used in the case of constipation; this is thought to be because inositol is important for the transmission of the nervous impulses that make the peristalsis in the intestines happen.
Inositol is best taken with all the rest of the B vitamin complex and with vitamin E.
Inositol is also good for the condition of the hair and nails, probably because of its influence over fat metabolism. Inositol deficiency can cause raised cholesterol levels and eczema.
The only known consequence of inositol overdose is diarrhoea. This is purely a mechanical effect; really large amounts are poorly absorbed and retain large amounts of fluid in the intestinal contents, making them looser.
Enemies of inositol include caffeine and antibiotics.
Food sources of inositol include any food high in B complex, which are mainly plant foods. Inositol is particularly high in fibres such as cereal brans, but is tightly bound in the form of phytic acid; for this reason, such foods are not a particularly important source.