Probiotics shifted PCOS blood sugar, not the scales

Polycystic ovary syndrome clusters insulin resistance, raised androgens and low-grade inflammation, and much of its day-to-day management sits with diet and lifestyle rather than in a clinic. That has made gut-targeted supplements an obvious thing to test, on the logic that the gut microbiota influences glucose handling and inflammatory tone. Individual probiotic trials in this group have been small, used different strains and reported a scatter of outcomes, which makes it hard to tell a real effect from noise. Pooling them is the sensible next step.

The authors systematically searched PubMed, Scopus, ISI Web of Science, the Cochrane Library and Google Scholar through September 2018 for randomised clinical trials of probiotic or synbiotic supplementation in women with polycystic ovary syndrome. Eight randomised trials, contributing nine treatment arms, met the inclusion criteria. The pooled outcomes were anthropometric measures, including weight and body mass index, and biochemical measures covering fasting blood sugar, insulin, the homeostasis model assessment of insulin resistance, C-reactive protein and total testosterone. Results were combined as mean differences, with C-reactive protein expressed as a standardised effect.

Supplementation significantly reduced fasting blood sugar by 2.52 mg/dl (95% CI -4.10 to -0.95) and insulin by 2.27 uIU/mL (95% CI -3.40 to -1.14), with HOMA-IR falling by 0.69 (95% CI -0.98 to -0.40). C-reactive protein dropped, reported as a Hedges' value of -1.69 (95% CI -3.00 to -0.38), and total testosterone fell by 0.12 ng/mL (95% CI -0.17 to -0.08). The null is equally important: changes in weight and body mass index did not reach statistical significance. So the glucose, inflammatory and hormonal markers moved while body size did not.

This supports the idea that gut-targeted supplements act on glucose handling and inflammatory markers in polycystic ovary syndrome independently of any change in body weight, which is a useful distinction because most metabolic improvements in this condition are attributed to weight loss. The evidence base is thin, though: 8 trials is a small pool, the trials were individually small, and the search stopped in September 2018. Because strains, doses and durations differed across studies, the analysis cannot say which formulation did the work. Whether these marker changes translate into symptoms, cycles or long-term risk was not addressed.

For women with polycystic ovary syndrome, this is a reason to think probiotic or synbiotic supplementation may nudge fasting glucose, insulin, insulin resistance, inflammation and total testosterone in a favourable direction, on the basis of a modest set of trials. It is not a weight-loss intervention: body weight and body mass index were unchanged. The size of the shifts is small, and it is not clear which specific products or strains produced them, since the pooled trials differed. Anyone weighing this up alongside existing treatment is having a conversation with their clinician, not replacing one.