Myo-Inositol Explained Simply

1. What Is Myo-Inositol?

Myo-inositol is a ring-shaped sugar alcohol, also called a cyclitol. It is one of several forms of inositol. The body also produces it itself. It is also contained in plant foods. As a dietary supplement, it is available as a powder, capsules or tablets. It is frequently used for questions about hormones, fertility and metabolism.

2. Where Is It Found, and What Is It Made From?

Myo-inositol is found, for example, in grains, corn, legumes and meat. In the body, it is a building block of cell membranes and helps to relay the signal of the hormone insulin within the cell. Studies also use mixtures, for example with D-chiro-inositol or folic acid.

3. What Does Myo-Inositol Do? What Research Shows

Metabolism and Insulin Action

In several review articles, myo-inositol and related inositol forms lowered insulin resistance, fasting insulin and fasting blood glucose more than a placebo 11217. Blood lipid levels also improved 121732. In pregnant women, the glucose tolerance test turned out more favorably 42122282930. In comparison with the diabetes drug metformin, no difference was found 1324. What remains open is which dose and duration are best.

Polycystic Ovary Syndrome

In women with polycystic ovary syndrome (a common hormonal disorder, often with irregular cycles), inositol preparations lowered the male hormone testosterone more than a placebo in several review articles 91223. The transport protein SHBG also increased 191223. Weight and body mass index decreased somewhat more than under placebo 69. A regular cycle occurred more frequently 9. In comparison with the diabetes drug metformin, the cycle improved similarly in both groups 3739. However, the studies differ in form, comparator preparation and duration.

Fertility and Conception

In women undergoing fertility treatment with fertilisation in the laboratory, the chance of pregnancy with inositol was greater in one review article 16. There were also more embryos of good quality 16. Another review article found more mature eggs and more fertilised eggs 15. Two others found no higher pregnancy rate 719. In women with polycystic ovary syndrome before fertilisation in the laboratory, more women became pregnant with myo-inositol than with metformin in a randomised (participants assigned by lot) study 35. Compared with D-chiro-inositol, a related inositol form, myo-inositol produced more mature eggs and embryos of the best quality 36. Whether more children are also born is still open.

Anxiety and Panic

For anxiety and panic, a review found limited evidence of an effect of inositol in panic disorder and obsessive-compulsive disorder 33. In a randomized (participants assigned by lot) trial with 60 women with polycystic ovary syndrome, depression, anxiety and stress improved more with myo-inositol than with metformin 38. The evidence is preliminary: the study involved women with polycystic ovary syndrome, not people with anxiety disorders. Studies in panic and obsessive-compulsive disorder are still pending.

Other Investigations

In pregnancy, gestational diabetes occurred less often with myo-inositol than in the control groups in several reviews 238182130. A Cochrane review rates the reliability of these findings as low to very low 11. Birth weight was lower in one review 22, with no difference in others 212531. A large review on inositol in pregnancy found less gestational diabetes, insulin requirement and preterm births 26. Most data come from pregnancy groups, and with mixed preparations the proportion of myo-inositol cannot be separated out.

4. How Was Myo-Inositol Taken in the Studies?

In the studies, myo-inositol was predominantly taken as a pure substance in powder, capsule or tablet form. In addition, mixtures with D-chiro-inositol, folic acid, selenium or probiotics as well as combinations with metformin were tested. The doses and treatment durations differ between the studies and are given in the table.

5. Is Myo-Inositol Safe? Side Effects in the Studies

Myo-inositol was well tolerated in several review articles and caused side effects less often than metformin 202427. In very premature infants who received myo-inositol directly, more children died than under placebo in a large study; the study was terminated early 34. Details on the reported side effects are shown in the table.

All details with tables and sources: full expert page on Myo-inositol