Researchers at Thailand's Ramathibodi Hospital and Mahidol University, and the University of Illinois conducted a double-blind RCT to assess the impact of probiotic supplements on insulin resistance in pregnant women with diet-controlled gestational diabetes.
Probiotics versus placebo in pregnancy
They enrolled 57 expectant mothers with diet-controlled gestational diabetes at 24 to 28 weeks of pregnancy and randomly assigned them to receive either probiotic supplements (28 patients) containing Bifidobacterium and Lactobacillus, or a placebo (29 patients).
Each participant took one capsule containing either the probiotics or placebo after breakfast every morning; this continued for four consecutive weeks. They all received counselling on diet control and lifestyle modification from nurses and nutrition counsellors at Ramathibodi Hospital.
After two weeks of intervention, they also took a 24-hour dietary recall questionnaire for three consecutive days, which was used as their representative diets during the study period.
The researchers also analysed the participants' daily caloric intake, along with their carbohydrate, fat, protein and fibre consumption, using the Thai nutritional database developed by Mahido lUniversity's Institute of Nutrition.
The primary outcomes of the study were the mean differences in insulin resistance, fasting insulin and fasting plasma glucose between the supplemented and placebo groups; secondary outcomes were the changes in maternal weight after the intervention.
Subsequently, the researchers reported significant improvement in glucose metabolism in the group that had received probiotic supplementation — including fasting plasma glucose, fasting plasma insulin, and insulin resistance — compared to the placebo group.
In addition, they observed no significant difference between dietary intake obtained from the three-day food record two weeks after starting treatment — this included carbohydrates, fat, protein and fibre.
The total pregnancy weight gain between the two groups during randomisation was similar, as were neonatal birth weight and the rates of neonatal hypoglycaemia.
Dearth of data?
The researchers noted that despite the study having the strength of a double-blind RCT, it was limited by a lack of data on the gut microbiota composition of the participants, both at baseline and post-intervention.
As such, they could not evaluate the effect of the intervention on the intestinal microbial community and draw link this to changes in metabolic parameters.
Furthermore, they lacked information on changes in short-chain fatty acid (SCFA) levels in the participants, which could have aided in elucidating the mechanisms behind the association between probiotic use and improved insulin resistance.
The study's relatively short intervention period and two-strain probiotic supplementation (the latter "driven by their availability and approval") was also considered a possible limitation. The researchers wrote that "the optimum duration to achieve maximum metabolic effects without adverse outcomes, along with the most suitable probiotic compositions, should be explored in the future".
At the same time, the present study involved only diet-controlled women with gestational diabetes, so the results could not be generalised to other types of patients, such as those with more severe hyperglycaemia who require insulin.
In conclusion, they wrote: "We did not observe any effects on pregnancy outcomes, as the study was not powered to capture these. Whether improved maternal metabolic parameters associated with probiotics use will result in favourable pregnancy outcomes should be further investigated.
"The present study showed that two-strain probiotic supplements for four weeks in diet-controlled Thai women with (GDM) in the late second to early third trimester exerted beneficial effects on fasting glucose levels and markers of insulin resistance without any adverse effects.
"As GDM is a global problem with maternal and offspring consequences, the data of the present study should be replicated in various populations, with optimisation of strains and duration of probiotic use.
"The present results suggest that probiotic supplements may be considered as an adjunctive treatment for glycaemic control in women with GDM."
Source: Journal of Diabetes Investigation
"Effects of probiotic supplements on insulinresistance in gestational diabetes mellitus: Adouble-blind randomized controlled trial"
Authors: Athasit Kijmanawat, et al.