D-Pinitol first entered the market in 1998, marketed by Humanetics Corporation. It’s chemical name is 3-O-methyl- D-chiro-inositol which means that it is a methyl ether of DCI and it is estimated that about 1/3 of orally administered d-pinitol is converted within the body into DCI. Studies on the effects of pinitol on blood sugar metabolism have had quite mixed results. Study numbers are generally quite small, usually between 5 & 25 subjects so that may explain some of the variability in results. One study by Davis et al published in Diabetes Care in 2000 showed that supplementation with d-pinitol at a rate of 20mg/kg bodyweight increases the blood concentration of both d-pinitol (48 x) and d-chiro inositol (14 x) after a period of 4 weeks. Unfortunately, however, this did not appear to affect any of the baseline parameters for measuring glucose metabolism.
Another more recent study by researchers at the Hong-Ik Hospital in Seoul found that the same level of supplementation, but over a period of 12 weeks did have a significant effect on reducing fasting glucose levels, blood glucose levels after meals and the longer term measure of blood glucose levels gylcosylated haemoglobin which basically provides an average of the blood sugar level for the past three months. Another Korean research group has found that pinitol supplementation is most effective at lowering blood sugar levels after meals when it is taken an hour before a carbohydrate rich meal, but that it had no appreciable effect on insulin levels measured after the meal. This may mean that it enhances the insulin sensitivity of cells by participating in the insulin signalling pathway rather than merely increasing the production of insulin in response to a carbohydrate load. This would be especially beneficial for women with PCOS who are likely to already have elevated levels of insulin.