Does Inositol Help Prevent Gestational Diabetes: A Review for Dietitians

Gestational diabetes mellitus (GDM), a form of glucose intolerance diagnosed in pregnancy. Uncontrolled GDM poses risks for both mother and child, including preeclampsia, preterm birth, macrosomia, neonatal hypoglycemia, and increases the mother’s long-term risk of Type 2 diabetes. 

There is emerging evidence that inositol may have a role in the prevention of GDM. This article will review the evidence for inositol and its effects on GDM, recommended dosages, safety, and research gaps.

What is Gestational Diabetes?

Gestational diabetes mellitus (GDM) is a condition of glucose intolerance first identified during pregnancy, caused by hormonal changes from the placenta that increase insulin resistance. The Canadian Diabetes Association recommends a two-step diagnostic approach: a 50 g glucose challenge test followed by a 75 g oral glucose tolerance test (OGTT) if the initial result is abnormal, with specific glucose thresholds for diagnosis. 

Early diagnosis and effective management through nutrition and lifestyle changes are essential to reduce complications such as macrosomia and long-term diabetes risks for both parent and baby.

What is Inositol?

Inositol, a sugar alcohol, occurs naturally in a variety of foods such as fruits, beans, grains, and nuts, and is synthesized within the human body. Inositol is primarily found in the form of myo-inositol (MI) and D-chiro-inositol (DCI).

These two stereoisomers are involved in cellular signaling and insulin regulation. They contribute to insulin signaling by increasing the translocation of glucose transporter type 4 (GLUT4) to the cell membrane, facilitating cellular glucose uptake. This insulin-sensitizing function positions inositol as a promising intervention for GDM, which is largely driven by insulin resistance. 

Research on Inositol’s Impact on Gestational Diabetes

Several studies have found that myo-inositol supplementation may help reduce the risk of GDM. For instance:

• In a randomized controlled trial (RCT) of 220 pregnant women with BMIs between 25 and 30, received 2g of myo-inositol plus 200 µg of folic acid or just 200 µg  twice daily from the first trimester through delivery. Results showed a 67% reduction in GDM incidence (11.6% in the treatment group vs. 27.4% in the placebo group)

  
  

• A Cochrane review of four RCTs found that myo-inositol supplementation reduced GDM rates from 28% in control groups to between 8–18% in treatment groups, particularly when started early in pregnancy 

  
  

• This meta-analysis of five RCTs reported that inositol supplementation decreased the GDM rate by 51%. The review also highlighted the potential preventive effects on preterm delivery supporting its benefits beyond glucose control

  
  

• Another systematic review of 7 studies including 1321 participants reported that a 4 g daily dose of myo-inositol significantly risk of GDM and well as fasting and postprandial glucose levels in OGTT measurements

  
  

• Another 2015 meta-analysis demonstrated a 71% reduction in GDM incidence among women taking myo-inositol. This review also highlighted improved insulin sensitivity and lower fasting glucose levels

Limitations of the research: 

While inositol shows promise, there are notable gaps in the research that warrant further exploration:

• Sample sizes: Most studies have small sample sizes 

• Risk of bias: Many studies had a high risk of bias. For example, many studies included in the systematic reviews and meta-analyses were not double-blinded

• Population Diversity: Many studies have been conducted in Italian populations, which limits the generalizability of findings 

• Long-Term Impact on Offspring: The long-term effects on offspring, such as the risk of childhood obesity or metabolic syndromes, remain unclear. More longitudinal studies are necessary to assess these outcomes 

• Comparative Studies on Dosage and Formulation: While most studies use 4g of MI daily, some have examined combinations of MI and DCI. However, evidence on whether such combinations offer enhanced benefits is limited and inconsistent 

Safety and Recommended Dosage

While more research is needed, inositol is generally well-tolerated and safe. Mild gastrointestinal discomfort is the most common side effect. Adverse maternal or fetal effects have not been reported. 

Most research supports a dosage of 4g of myo-inositol daily, typically divided into two 2g doses, similar to the dose recommended for Polycystic Ovarian Syndrome. Some studies have examined combinations of MI and DCI, although results indicate that MI alone may be more effective at this dosage.

If an individual wishes to use inositol during pregnancy, it is recommended that they consult with their OBGYN, endocrinologist or GDM team. 

Key Summary Points

• Gestational Diabetes Mellitus (GDM) is a condition of glucose intolerance caused by hormonal changes during pregnancy, increasing insulin resistance

• IMyo-inositol (MI) and D-chiro-inositol (DCI) enhance insulin signaling and glucose uptake. Evidence suggests inositol supplementation, particularly 4 g of MI daily, can significantly reduce GDM incidence and improve glucose tolerance

• Multiple randomized controlled trials and meta-analyses indicate up to a 71% reduction in GDM risk with inositol supplementation. However, limitations in the research include small sample sizes, population diversity issues, and a lack of long-term data on offspring outcomes

• Inositol is generally safe and well-tolerated, with mild gastrointestinal discomfort as the most common side effect. Clients should consult their healthcare team before initiating supplementation

• Future Directions: More high-quality research is needed to confirm long-term benefits, optimal dosages, and the impact on diverse populations.

Conclusion

Inositol supplementation, especially with myo-inositol, is emerging as a promising intervention for reducing GDM risk, improving glucose tolerance, and potentially supporting other positive pregnancy outcomes.

For dietitians, understanding these emerging therapies can enhance support for pregnant clients, particularly those at higher risk of GDM. While current research underscores the efficacy of inositol, further studies are needed to address existing gaps in the literature.