Inositol nutritional importance

Myo-inositol is one of the most biologically active forms of inositol. It exists in several isomeric forms, the most common being the constituent of phospholipids in biological cell membranes. It also occurs as free inositol and as inositol hexaphosphate (IP6) also known as phytate which is a major source from food. Rice bran is one of the richest sources of IP6 as well as free inositol. Inositol is considered to belong to the B-complex vitamins. It is released in the gastrointestinal tract of humans and animals by the dephosphorylation of IP6 (phytate) by the intestinal enzyme phytase. Phytase also releases intermediate products as inositol triphosphate and inositol pentaphosphate. Inositol triphosphate in cellular membrane functions as an important intra- and intercellular messenger, that merits its value as a nutritional therapy for cancer. 

Some dietary components arc difficult to characterize as cs-.sential nutritional factors in human metabolism because the organism can produce these compounds from other dietary components. (Consider vitamin D and nicotinic acid, which are discu.sscd above.) Vitamin D and nicotinic acid, however. generally are considered among the cla.ssic vitamins. Moreover, there is no clear consensus on the necessity for inositol, choline, and p-aminohen/oic acid. Nevertheless, such dietary components do perfonn important metabolic functions hence, a brief characterization of the.se follows. 

There are 13 vitamins known to be Important In human nutrition. Included In this class of essential nutrients are vitamin A, B-complex (actually composed of a group of 8 vitamins), vitamin C, vitamin D, vitamin E, and vitamin K. We can subdivide vitamins Into 1) the lipid (fat)-soluble compounds (vitamins A, D, E, and K), meaning they dissolve readily In fat and 2) the water-soluble compounds, vitamin B-complex (thiamin, riboflavin, niacin, vitamin B, panthothenlc acid, vitamin B] 2> biotin, and folic acid) and vitamin C, which dissolves readily In aqueous solutions. It has been three decades since the last vitamin (B] 2) discovered In 1948 and as stated by Herbert (1980), It Is probable that no new vitamins will be found. There are substances which are growth factors for other forms of life, such as bacteria, but not for humans. Para-amlnobenzolc acid (PABA), bioflavonoids (vitamin P), choline. Inositol, llpolc acid, and ubiquinone are just a few of these examples. 

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