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

Abstract Objective Breast cancer (BC) is the most diagnosed cancer in women. Increasing survival rates shifts attention to preventive strategies. Obesity and intestinal microbiota (IM) composition may be associated with BC. Mediterranean Diet (MD) proved to be protective. The aim of this study was to assess the efficacy of probiotics in addition to MD versus diet alone in influencing gut microbiota and metabolic profile in overweight BC survivors. Methods 34 BC survivor were randomized to MD for 4 months plus 1 sachet/day of probiotics (Bifidobacterium longum BB536, Lactobacillus rhamnosus HN001) for the first 2 months (intervention group, n=16) or MD alone for 4 months (control group, n=18). Anthropometric and nutritional assessments, adherence to MD, compliance to physical activity and metabolic parameters dosage were performed at baseline (T0), at 2 (T2) and at 4-months (T4). IM analysis was performed at T0 and T2. Results After 2-months 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-/-Firmicutes ratio significantly decreased in the intervention group and increased in controls (p=0.004). Significant reductions of body weight, body mass index (BMI), fasting glucose and Homeostasis-Model Assessment Insulin-Resistance (HOMA-IR) were observed at T4 in both groups, in the intervention group also waist circumference (p=0.012), waist/hip ratio (p=0.045) and fasting insulin (p=0.017) significantly decreased. Conclusions Probiotics in addition to MD positively influence the gut microbiota and improve metabolic and anthropometric parameters respect to MD alone.