Gut microbiota composition after diet and probiotics in overweight breast cancer survivors: a randomized open-label pilot intervention trial

Objectives Breast cancer (BC) is the most diagnosed cancer in women. Increasing survival rates shift attention to preventive strategies. Obesity and intestinal microbiota composition may be associated with BC. A Mediterranean diet (MD) proved to be protective. The aim of this study was to assess the efficacy of probiotics in addition to an MD versus diet alone in influencing gut microbiota and metabolic profile in overweight BC survivors. Methods A total of 34 BC survivors were randomly assigned to an MD for 4 mo plus 1 sachet/d of probiotics (Bifidobacterium longum BB536, Lactobacillus rhamnosus HN001) for the first 2 mo (intervention group, n = 16) or an MD alone for 4 mo (control group, n = 18). Anthropometric and nutritional assessments, adherence to the MD, compliance with physical activity, and metabolic parameters dosage were performed at baseline (T0), at 2 mo (T2), and at 4 mo (T4). Intestinal microbiota analysis was performed at T0 and T2. Results After 2 mo of probiotic administration the number of bacterial species (P = 0.01) and the bacterial diversity assessed with the Chao1 index (P = 0.004) significantly increased; no significant variations were detected after diet alone. The Bacteroidetes-to-Firmicutes ratio significantly decreased in the intervention group and increased in controls (P = 0.004). Significant reductions of body weight, body mass index, fasting glucose, and homeostasis model assessment of insulin resistance were identified at T4 in both groups; in the intervention group waist circumference (P = 0.012), waist-to-hip ratio (P = 0.045), and fasting insulin (P = 0.017) also significantly decreased. Conclusions Probiotics in addition to an MD positively influence gut microbiota and improve metabolic and anthropometric parameters compared with an MD alone.