What is the role of inositol (myo-inositol) in human health?

From the Guidelines

Inositol supplementation, particularly myo-inositol, is recommended for women with polycystic ovary syndrome (PCOS) to improve insulin sensitivity, regulate menstrual cycles, and support fertility, based on the most recent evidence 1. Inositol is a naturally occurring sugar alcohol that functions as a key cellular signaling molecule in the body. It's available as a dietary supplement in two main forms: myo-inositol and D-chiro-inositol.

Key Points to Consider

• Inositol supplements are typically taken at doses ranging from 2-4 grams daily for myo-inositol or 600-1200 mg daily for D-chiro-inositol, often divided into two doses.
• These supplements have shown promise for several health conditions, particularly polycystic ovary syndrome (PCOS), where they may help improve insulin sensitivity, regulate menstrual cycles, and support fertility, as noted in a systematic review and meta-analysis 1.
• Inositol may also benefit metabolic health by helping regulate blood sugar levels and potentially supporting mood regulation in conditions like depression and anxiety.
• The supplement works by influencing insulin signaling pathways and neurotransmitter systems in the brain.
• While generally considered safe with minimal side effects (occasionally mild digestive discomfort at higher doses), inositol supplements should be discussed with a healthcare provider before starting, especially for pregnant women or those with existing medical conditions. Some studies suggest that inositol intake may be lower in women with PCOS due to poorer dietary intakes of core food groups that contain inositol, including beans, whole grains, nuts, and seeds 1.

Important Considerations

• The lack of a universal definition for diet quality, dietary and PA assessment tools, and PCOS criteria are limitations that should be considered when interpreting the results of studies on inositol supplementation 1.
• Failure to account for variations in age, adiposity, lifestyle, socioeconomic status, race and ethnicity, acculturation status, the proportion of PCOS phenotypes across studies, the use of retrospective data or data primarily collected from clinical settings may have contributed to heterogeneity in the observations 1.
• More research is needed to confirm the observations and to understand the role of inositol supplementation in the management of cardiometabolic and reproductive deregulation in PCOS 1.

From the Research

Inositol Studies

• Inositol has been studied for its potential effects on mental health parameters and biomarkers of oxidative stress in women with polycystic ovary syndrome (PCOS) 2.
• A randomized, double-blind, placebo-controlled trial compared myo-inositol and metformin on mental health parameters and biomarkers of oxidative stress in 60 women with PCOS, finding that myo-inositol supplementation had favorable effects on parameters of mental health and plasma total antioxidant capacity (TAC) levels 2.
• Another study found that inositol may have insulin sensitizing effects, but its efficacy in the management of PCOS remains indeterminate, with evidence suggesting benefits for myo-inositol or D-chiro-inositol (DCI) for some metabolic measures and potential benefits from DCI for ovulation 3.

Comparison to Other Supplements

• Omega-3 fatty acids have been studied for their potential effects on depression and anxiety, with some evidence suggesting a small to modest benefit for depressive symptomology, but the evidence is generally considered low to very low certainty 4.
• A systematic review of omega-3 fatty acids and anxiety found that four mechanisms were identified as potential underlying factors, including inflammatory response, brain-derived neurotrophic factor (BDNF), cortisol, and cardiovascular activity 5.
• Omega-3 supplementation has also been studied in the treatment of PCOS, with some evidence suggesting indirect benefits regarding the glycemic profile, lipid profile modulation, and regulation of the androgenic profile, but further studies are needed to reveal well-defined standards for dosage and supplementation time 6.

Key Findings

• Myo-inositol supplementation may have favorable effects on parameters of mental health and plasma TAC levels in women with PCOS 2.
• Inositol may have insulin sensitizing effects, but its efficacy in the management of PCOS remains indeterminate 3.
• Omega-3 fatty acids may have a small to modest benefit for depressive symptomology, but the evidence is generally considered low to very low certainty 4.
• Omega-3 supplementation may have indirect benefits in the treatment of PCOS, but further studies are needed to reveal well-defined standards for dosage and supplementation time 6.