Myo-inositol is a phospholipid derived 6-carbon polyalcohol, sometimes grouped with the dietary carbohydrates because of its similarity in structure to the simple sugars. Myo-inositol is one of the structural isomers of inositol and is most commonly associated with the phospholipid phosphatidylinositol. Its similarity in structure to some sugars gives it similar physical properties, and dietary myo-inositol has a sweetness about half that of sucrose. Because of its role as a component of phosphatidylinositol, myo-inositol is found in all living cells as part of the cell membrane. The amount of myo-inositol in the typical Western diet is unknown, but some estimates of the myo-inositol in the typical American diet estimate it to be around 900 mg per day, with just over half of this being linked to lipids, as would be expected from a phospholipid bound substance. Absorption rates of myo-inositol are high, and estimated to be almost 100 %, with absorbed myo-inositol having a plasma half-life of about 20 mins.
Although the concentrations of myo-inositol are low in plasma (~0.03 mmM), and fall quickly postprandially, the concentration of myo-inositol in the peripheral nerves are extremely high in mammals (~3.0 mM). This suggests that there is an active transport process for myo-inositol into nerve tissue. Myo-inositol may therefore be vital for correct nerve function. Experimental animals with diabetes do show peripheral nerve damage and low levels of myo-inositol, a situation that can be corrected through administration of high intakes of dietary myo-inositol. In human studies, increasing the myo-inositol content of the diet from 772 to 1648 mg significantly improves sensory function in patients with diabetic neuropathy. Eating foods that are high in myo-inositol may therefore be of benefit to those with nerve disorders, particularly those with peripheral neuropathy as a result of blood sugar aberrations. In this respect knowing the food which contain myo-inositol may be useful.
To these ends, studies have estimated the myo-inositol content of a number of foods common in the Western diet. From one study the total myo-inositol content of the diet was estimated to be between 200 and 1500 mg per 1800 kcal1. Even selecting low inositol foods the authors of the research could not reduce the myo-inositol content of the diet below 200 mg per day. The myo-inositol content was highest in legumes, nuts, seeds, grains and fruits, although the content did vary between foods of these groups. Of the fruits, citrus fruits excluding lemons, and cantaloupes were very high in myo-inositol. Further fresh examples of these foods contained higher myo-inositol content that tinned or frozen alternatives. Milk, meat and fatty animal foods were found to contain low concentrations of myo-inositol. The authors concluding by mentioning that because endogenous synthesis of myo-inositol in some neuropathies might be apparent, dietary compensation might be an effective treatment for certain nerve disorders.
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