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Myo-inositol for insulin resistance, metabolic syndrome, polycystic ovary syndrome and gestational diabetes
  1. James J DiNicolantonio and
  2. James H O'Keefe
  1. Department of Preventive Cardiology, Saint Lukes Mid America Heart Institute, University of Missouri–Kansas City, Kansas City, Missouri, USA
  1. Correspondence to Dr James J DiNicolantonio; jjdinicol{at}gmail.com

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Myo-inositol, also known as inositol (cyclohexanehexol), is a cyclic carbohydrate with six hydroxyl groups.1 For a long time, it was considered a B vitamin (vitamin B8). However, it is not considered an essential nutrient because it is formed from glucose. Each kidney makes around 2 g of myo-inositol per day, and the average dietary intake is 0.5–1.0 g/day.2 3 The liver and brain also synthesise myo-inositol, although at much lower amounts compared with the kidneys. Importantly, however, in the brain, myo-inositol levels reach concentrations 10-fold to 15-fold greater than that of blood, and there is limited uptake of myo-inositol from systemic circulation.3

Unfortunately, no requirement for dietary inositol in humans has been determined despite demonstration of signs of inositol deficiency in several animal species.4 Importantly, dietary caffeine intake (particularly coffee) increases the need for myo-inositol.5 Increasing age, antibiotic use, sugar and refined carbohydrate intake, sodium deficiency, insulin resistance, and type 1 and type 2 diabetes all increase the need for myo-inositol.6 Importantly, tissues highest in inositol, such as kidneys, brain and blood cells, are typically no longer consumed by humans. Furthermore, other foods that are high in inositol-forming substances, such as liver, grains, seeds and beans, are not readily consumed. Thus, from a dietary perspective, our intake of inositol is much lower compared with what humans would have consumed during Palaeolithic times.

We get myo-inositol in the diet either as inositol-containing phospholipids or phytic acid—which is inositol hexaphosphate (IP6). Bacterial phytases and phosphatases are primarily responsible for digesting dietary IP6 in the body and for releasing myo-inositol and phosphate. All living cells (animal, plant, bacteria and fungi) contain inositol phospholipids in their membranes either in their free form or bound as phospholipids or inositol phosphates. Phytic acid, the main storage form of phosphorus and …

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