What is Inositol and How to Take It
Inositol is a naturally occurring sugar-like compound found in whole grains, seeds, fruits, beans, and nuts that functions as a cellular nutrient and second messenger in insulin and hormone signaling pathways, with established benefits primarily in polycystic ovary syndrome (PCOS) management through improved insulin sensitivity and ovulation restoration. 1, 2, 3
What Inositol Is
Inositol is an essential nutrient required by human cells for growth and survival, serving as a source of several second messengers including diacylglycerol and inositol triphosphate 1, 3
Two main forms exist in the body: myo-inositol (MI) and D-chiro-inositol (DCI), which naturally occur in a physiological ratio of approximately 40:1 in serum 3, 4
Myo-inositol is a precursor of inositol triphosphate, a second messenger that regulates hormones including TSH, FSH, and insulin 4
In ovarian tissue specifically, the MI/DCI ratio is 100:1, though this becomes dramatically altered in hyperinsulinemic conditions like PCOS 5
Established Clinical Benefits
For PCOS and Fertility
The American College of Obstetricians and Gynecologists recognizes inositol as a non-pharmaceutical alternative to metformin for improving insulin sensitivity in PCOS, with a favorable safety profile and no weight gain 2
Inositol improves metabolic and hormonal status in PCOS and restores spontaneous ovulation by addressing the underlying insulin resistance 5, 3
High concentrations of myo-inositol in follicular fluid make it a quality marker for oocyte evaluation, and supplementation improves ovarian stimulation parameters in assisted reproductive technology 5, 3
The Endocrine Society suggests inositol supplementation should be part of a comprehensive approach that includes lifestyle modifications such as weight loss when indicated 2
For Premature Infants
- Inositol supplementation at 80 mg/kg/day for 5 days in premature infants with respiratory distress syndrome increased survival and lowered the subsequent incidence of bronchopulmonary dysplasia 1
Potential Cancer Chemoprevention
- The American College of Chest Physicians notes that myo-inositol shows promise in lung cancer chemoprevention through inhibition of the PI3K pathway in bronchial epithelial cells, though this remains investigational and is not recommended outside clinical trials 1
How to Take Inositol
Dosing for PCOS and Fertility
For PCOS management, typical dosing ranges from 2-4 grams daily of myo-inositol, though specific optimal doses vary by formulation 5, 4
A 3.6:1 myo-inositol to D-chiro-inositol ratio has shown positive results in women undergoing in vitro fertilization with previous ART failures, when supplemented for 1-3 months before IVF 6
The physiological 40:1 MI/DCI ratio appears optimal for treating PCOS disorders based on the body's natural distribution 4
Safety Profile
Inositol demonstrates excellent safety even at high doses, with only the highest dose of 12 g/day causing mild gastrointestinal side effects such as nausea, flatus, and diarrhea 7
The severity of side effects does not increase with dosage, and inositol is generally well-tolerated across clinical applications 7
Inositol is considered safe in pregnancy based on its use in premature infants and natural presence in the body 1
Important Drug Interaction
If taking lithium therapy, exercise caution with magnesium-containing inositol supplements, as magnesium can interact with lithium through similar renal mechanisms and potentially affect lithium levels 8
The American Academy of Child and Adolescent Psychiatry recommends monitoring for signs of reduced lithium efficacy (mood instability, return of manic or depressive symptoms) if combining these supplements 8
Consider discontinuing supplements if mood stability deteriorates in patients on lithium therapy 8
Dietary Sources
Natural dietary sources include whole grains, seeds, fruits, beans, nuts, legumes, cereals, and vegetables 1, 2, 3
Phytate (inositol hexaphosphate) from high-fiber foods like cereals and legumes may provide additional benefits by inhibiting calcium stone formation, though this represents a different form 1
Clinical Context
For patients with PCOS and insulin resistance who have poor dietary intake of inositol-containing foods, supplementation provides a rational, evidence-based intervention that addresses the underlying pathophysiology rather than just symptoms 2. The compound's role as an insulin second messenger and its involvement in follicular gonadotropin pathways make it mechanistically sound for reproductive dysfunction 5, 3.