D-chiro-inositol

This is an absence of evidence, not evidence that D-chiro-inositol does nothing. Myo-inositol sat outside the review entirely, so nothing here describes the form most people actually take. The search closed in January 2017.

These figures are reported as background inside a guideline evidence review, not measured by a study designed for the question. That same review rated every comparison of different inositol ratios at the lowest certainty its framework offers.

An umbrella review inherits the weaknesses of the trials underneath it, and counts the same small trials again each time they turn up in a different meta-analysis. Over half of the 13 meta-analyses it appraised were themselves rated low or very low quality.

A guideline synthesises trials rather than adding any, and only 3 of the 13 comparisons its evidence review assessed had enough studies to pool. The same guideline records that inositol's side effects and safety are not known, and that supplement regulation, dose and quality control differ from those for medicines.

Ovulation and a regular cycle are steps toward pregnancy, not pregnancy. The ovulation pooling was highly inconsistent between trials, and the whole analysis rests on ten small trials totalling 601 women. Neither pooling reported a live birth.

A registry entry records that a trial was declared, not what it found, so none of these counts is evidence about how inositol works. Trials often publish in journals without ever posting back to the registry, so a raw non-posting count overstates true non-reporting. This registry is US-centred and under-covers the Italian and Indian trials that dominate this field.

Eleven of the 13 trials in the Cochrane review gave inositol as preparation for in vitro fertilisation, so it does not describe ordinary supplement use. Cochrane translated its own estimate into absolute terms: against a 12% live birth rate without inositol, the rate with it would sit somewhere between 9% and 51%.

Whether inositol raises live births is unsettled. One umbrella review says it more than doubles them, Cochrane calls the outcome too uncertain to judge, and none of the 85 outcomes graded in this field reaches high quality.

These were women undergoing fertility treatment, so this describes a fertility-treatment add-on rather than everyday supplementation. Sixty were randomised and about 44 analysed, a thin base for a gap that wide. There was no plain myo-inositol arm, so it cannot say whether either blend beats myo-inositol on its own. Several of the authors are affiliated with a nutrition-sector company.

The 40:1 ratio the market is built on has been tested far less than the argument over it suggests. The only two trials comparing ratios head to head point opposite ways, and both sit at the lowest certainty rating.

Neither is a new trial: both are re-poolings of a literature made mostly of small studies. The earlier one stopped searching in October 2021, so it predates both the guideline's own review and the 2025 pregnancy trial. The later one could pool only 3 of the 13 comparisons it assessed.

Two reviews of the same inositol trials disagree on whether it works. The one calling it effective reports no live birth or pregnancy outcome, so the split is less about the trials than about what a reviewer calls enough.

A network meta-analysis mostly compares treatments that were never tested against each other directly, so this is an indirect estimate. Twenty-two trials and 1079 women spread across four classes of treatment leaves each comparison thin. Nothing here goes beyond a surrogate: no pregnancy, no live birth.