Myo-Inositol

Natural compound similar to vitamin B that improves insulin signaling and helps regulate the hormonal axis. Used in PCOS to support ovulation and cycles; useful for gestational diabetes risk.

Quick facts

  • They are part of molecules that help cells "receive and understand" signals from hormones like insulin and gonadotropins.

Myo-inositol is a natural compound similar to a B vitamin that our body produces in small amounts and that we also obtain from foods such as fruits, legumes, whole grains, and nuts. Although it is not a vitamin as such, it participates in key functions related to metabolism, hormones, and cell function.

In recent years, it has been studied mainly for its role in female reproductive health, polycystic ovary syndrome (PCOS), and blood sugar control.

How does it work?

In the body, myo-inositol forms part of molecules that help cells “receive and understand” signals from hormones such as insulin and gonadotropins (involved in ovulation).

This can translate into:

  • Better insulin utilization, helping to keep blood sugar levels stable.
  • Hormonal regulation, promoting more regular menstrual cycles in women with PCOS.
  • Improved ovarian response, by optimizing how the ovary receives signals to produce mature eggs.

Important: There is another form, D-chiro-inositol, which is also used in supplements, and where some studies have observed that it, when given in excess or alone, could increase androgens (male hormones) in the ovaries, which would be counterproductive. Therefore, many experts recommend using it in combination with myo-inositol, but in a 40:1 ratio, which appears to be closest to ovarian physiology.

Furthermore, there is evidence that high doses or incorrect combinations can reduce intestinal absorption of myo-inositol.

Benefits According to Science

Polycystic Ovary Syndrome (PCOS)

A review and meta-analysis by Unfer and his team in 2017, which analyzed several clinical trials, found that myo-inositol can improve ovulation, reduce testosterone levels, and regulate menstrual cycles in women with PCOS, especially when combined with healthy lifestyle habits.

Fertility and Assisted Reproduction Treatments

Laganà and colleagues (2018) reviewed trials in women undergoing in vitro fertilization (IVF) and observed that myo-inositol reduced the amount of medication needed to stimulate the ovaries and improved egg quality.

Prevention of Gestational Diabetes

Vitagliano and collaborators in 2019 and Wei and his team in 2022 conducted meta-analyses of trials in pregnant women at risk of gestational diabetes and found that myo-inositol significantly reduced the risk of developing it, with no serious adverse effects.

Metabolism and Lipid Profile

Tabrizi and collaborators in 2018 analyzed studies in people with metabolic diseases and found moderate improvements in cholesterol and triglyceride levels with supplementation.

Mental Health

Although less studied, some trials have explored its role as a supplement for mild depression and anxiety, but the evidence in this field is still limited and inconclusive.

Dosage and Forms of Consumption

  • In PCOS: the most used in studies is 2 grams of myo-inositol twice a day (4 g daily), often combined with 200-400 mcg of folic acid. In combination with D-chiro-inositol, the 40:1 ratio is usually used, meaning for every 2,000 mg of myo-inositol, 50 mg of D-chiro is added.
  • In prevention of gestational diabetes: similar doses (4 g/day in two divided doses).
  • It can be found in powder, sachets, or capsules.
  • Absorption can be reduced if taken with high doses of D-chiro-inositol or glucose transport inhibitors (Garzon et al., 2019).

Safety and Potential Side Effects

  • Myo-inositol is considered safe and well-tolerated at usual doses.
  • The most frequent side effects are mild: digestive discomfort, gas, or nausea at the beginning, which usually improve over time or by dividing the doses.
  • There is insufficient data on its long-term use in children, so it is not recommended without medical supervision.
  • In pregnant and breastfeeding women, its use is safe at the doses studied for gestational diabetes.

Conclusions

Myo-inositol is a supplement with a solid scientific basis in areas such as PCOS, fertility, and the prevention of gestational diabetes, with a very favorable safety profile.

In PCOS, it can help improve ovulation and hormone levels, and in pregnant women at risk, reduce the likelihood of developing gestational diabetes. It can also provide moderate benefits for blood fat profiles.

It is not a miracle cure nor does it replace other measures such as diet or exercise, but it can be a useful complement within a comprehensive approach.

Combined use with D-chiro-inositol should be approached cautiously, as high doses of the latter could have undesirable effects on androgens in some women.

It is always recommended to have the guidance of a healthcare professional before starting supplementation.

References
  1. Firth J, Teasdale SB, Allott K, Siskind D, Marx W, Cotter J, Veronese N, Schuch F, Smith L, Solmi M, Carvalho AF, Vancampfort D, Berk M, Stubbs B, Sarris J. The efficacy and safety of nutrient supplements in the treatment of mental disorders: a meta-review of meta-analyses of randomized controlled trials. World Psychiatry. 2019 Oct;18(3):308-324. doi: 10.1002/wps.20672. PMID: 31496103; PMCID: PMC6732706.
  2. Garzon S, Laganà AS, Monastra G. Risk of reduced intestinal absorption of myo-inositol caused by D-chiro-inositol or by glucose transporter inhibitors. Expert Opin Drug Metab Toxicol. 2019 Sep;15(9):697-703. doi: 10.1080/17425255.2019.1651839. Epub 2019 Aug 8. PMID: 31382802.
  3. Laganà AS, Vitagliano A, Noventa M, Ambrosini G, D'Anna R. Myo-inositol supplementation reduces the amount of gonadotropins and length of ovarian stimulation in women undergoing IVF: a systematic review and meta-analysis of randomized controlled trials. Arch Gynecol Obstet. 2018 Oct;298(4):675-684. doi: 10.1007/s00404-018-4861-y. Epub 2018 Aug 4. PMID: 30078122.
  4. Miñambres I, Cuixart G, Gonçalves A, Corcoy R. Effects of inositol on glucose homeostasis: Systematic review and meta-analysis of randomized controlled trials. Clin Nutr. 2019 Jun;38(3):1146-1152. doi: 10.1016/j.clnu.2018.06.957. Epub 2018 Jun 21. PMID: 29980312.
  5. Nordio M, Proietti E. The combined therapy with myo-inositol and D-chiro-inositol reduces the risk of metabolic disease in PCOS overweight patients compared to myo-inositol supplementation alone. Eur Rev Med Pharmacol Sci. 2012 May;16(5):575-81. PMID: 22774396.
  6. Tabrizi R, Ostadmohammadi V, Lankarani KB, Peymani P, Akbari M, Kolahdooz F, Asemi Z. The effects of inositol supplementation on lipid profiles among patients with metabolic diseases: a systematic review and meta-analysis of randomized controlled trials. Lipids Health Dis. 2018 May 24;17(1):123. doi: 10.1186/s12944-018-0779-4. PMID: 29793496; PMCID: PMC5968598.
  7. Unfer V, Facchinetti F, Orrù B, Giordani B, Nestler J. Myo-inositol effects in women with PCOS: a meta-analysis of randomized controlled trials. Endocr Connect. 2017 Nov;6(8):647-658. doi: 10.1530/EC-17-0243. PMID: 29042448; PMCID: PMC5655679.
  8. Vitagliano A, Saccone G, Cosmi E, Visentin S, Dessole F, Ambrosini G, Berghella V. Inositol for the prevention of gestational diabetes mellitus: a systematic review and meta-analysis of randomized controlled trials. Arch Gynecol Obstet. 2019 Jan;299(1):55-68. doi: 10.1007/s00404-018-5005-0. Epub 2018 Dec 18. PMID: 30564926.
  9. Wei J, Yan J, Yang H. Inositol Nutritional Supplementation for the Prevention of Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients. 2022 Jul 9;14(14):2831. doi: 10.3390/nu14142831. PMID: 35889788; PMCID: PMC9318937.