Effect of dietary myo-inositol supplementation on the insulin resistance and the prevention of gestational diabetes mellitus: an open-label, randomized controlled trial

Purpose Myo-inositol (MI) is an insulin-sensitizing dietary supplement, enhancing the transfer of glucose into the cell. Gestational diabetes mellitus (GDM) is characterized by abnormal glucose tolerance, which is associated with elevated insulin resistance. The present study aimed to assess the effect of MI supplementation during pregnancy on the incidence of GDM. Methods We performed a single-center, open-label, randomized controlled trial. A cohort of 200 pregnant women at 11-13(+6) weeks of gestation were randomly assigned in two groups: MI group (n = 100) and control group (n = 100). The MI group received MI and folic acid (4000 mg MI and 400 mcg folic acid daily), while the control group received folic acid alone (400 mcg folic acid daily) until 26-28 weeks of gestation, when the 75 g Oral Glucose Tolerance Test (OGTT) was performed for the diagnosis of GDM. Clinical and metabolic outcomes were assessed. Results The incidence of GDM was significantly higher in the MI group (14.9%) compared to the control group (28.5%) (P = 0.024). Women treated with MI had significantly lower OGTT glucose values, than those not treated with MI (P < 0.001). The insulin resistance as assessed by HOMA-IR was significantly lower in the MI group versus control (P = 0.045). Furthermore, MI group had significantly higher insulin sensitivity as measured by the Matsuda Index, compared to the control group (P = 0.037). Conclusion MI supplementation seems to be an effective option to improve the glycemic control of pregnant women and prevent the onset of GDM.