Two controlled trials evaluating supplemental myo-inositol have recently been published. The first, in the journal Diabetes, Obesity & Metabolism, was a randomized and placebo-controlled trial evaluating the effect of a combination of myo-inositol and zinc on insulin resistance (HOMA-IR) among children with obesity. Fifty children completed this three-month study, which took place in Italy. Participants received either a placebo containing 1g galactooligosaccharides (GOS) or a combination including 2g myo-inositol (MI), 5mg zinc gluconate, as well as 1g GOS, and all participants followed a Mediterranean-style isocaloric diet. While there was no overall benefit in the experimental group, children with severe obesity had significantly lower fasting insulin and HOMA-IR in the myo-inositol group compared to placebo.
The second was a randomized and controlled trial comparing the use of metformin to the combination of MI and D-chiro-inositol (DCI) in a 40:1 ratio, a formula previously shown to improve hormonal and metabolic parameters among women with polycystic ovarian syndrome (PCOS). This recent trial equally divided 60 women with PCOS to receive either MI and DCI or metformin for 12 weeks. Both groups had significant and similar improvements in multiple parameters, including insulin sensitivity, menstrual regularity, BMI, quality of life, SHBG, etc. Metformin had a slightly better effect on insulin sensitivity, but this may have been from an overrepresentation of the type A phenotype of PCOS in that group. There was also a suggestion that MI and DCI may be more effective for the C and D phenotypes (ovulatory and non-hyperandrogenic PCOS), which would need to be confirmed in larger trials. The evidence for MI and DCI as a safe and effective alternative for PCOS and insulin resistance continues to grow.