Choline and inositol are members of the B vitamin group. Both get neglected in nutrition, inositol perhaps more than choline. Both choline and inositol function closely together in human metabolism because both form structural components of cell membranes. In this regard phosphatidylcholine and phosphatidylinositol form parts of the phospholipid molecules that encase all of our cells. Inositol is not an essential nutrient, because as with choline, it can be synthesised endogenously. However, evidence suggest that both choline and inositol may be conditionally essential in that under certain circumstances, endogenous production cannot keep pace with metabolic requirements. Under such conditions, dietary intakes of inositol may be necessary. High intakes of inositol do exert beneficial health effects, and as with choline, inositol appears to have beneficial effects as a lipotropic factor in the liver, where it can aid the breakdown of triglycerides and increase their export to the circulation as fatty acids.
In the diet, inositol is present as phytic acid (inositol hexakisphosphate [IP6] or inositol polyphosphate), a form of dietary fibre found in plant foods. Phytic acid is metabolised by the bacteria in the lower parts of the intestine, and this liberates inositol for absorption to the circulation. In addition, inositol is also present in foods of animal origin because it is a component of cell membranes in animal tissues. An isomer of inositol called myo-inositol is found in particularly high concentrations in nervous tissue. Approximately 900 mg of myo-inositol is present in the typical American 2500 kcal diet1. Studies have shown that when the dietary content of myo-inositol are increased, sensory nerve function improves significantly in diabetic subjects, suggesting that myo-inositol synthesis may be rate limiting in nervous tissue synthesis. Myo-inositol is also required for the function of the insulin receptor and high dietary intakes may have an insulin sensitising effect in mammals with insulin resistance.
Another role for inositol is that of correct function of the neurotransmitters serotonin and acetylcholine. Patients with depression have been shown to have low cerebrospinal fluid levels of inositol, and supplements of inositol may be beneficial at reducing the symptoms of depression. Inositol supplements may also be effective at reducing the severity and frequency of panic attacks, something they were able to do without side effects even at 12 gram intakes daily. Although isomers of inositol may have important and interesting effects on brain, nerve and hormonal systems, inositol is most well known and widely researched for its lipophilic effects. These effects, as with choline, are well documented in the nutritional literature. High intakes of dietary inositol are able to promote lipophilic effects on the liver which is critical to the health of the liver and free flow of bile, stagnation of the latter being associated with serious liver disorders such as cirrhosis of the liver and alcoholic and non-alcoholic fatty liver.
Dr Robert Barrington’s Nutritional Recommendation: Inositol is available in supplemental form, often as inositol monophosphate and is included in some high quality multivitamin and mineral formulas. The recommended intake of dietary inositol as a supplement is around 100 to 500 mg per day for the treatment of liver disorders and at a dosage of around 1000 to 2000 mg per day for the treatment of diabetes. Inositol should be taken at dosages of around 12 grams per day to reduce the frequency and severity of panic attacks.
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