Weight Loss and Omega-3 Supplementation Modulate the Microbiome in Women with Increased Breast Cancer Risk.

Pilotstudien randomiserade 34 kvinnor i peri- eller postmenopaus med BMI på minst 28 kg/m² till 3,25 g/dag omega-3-fettsyror eller placebo under en beteendebaserad viktminskningsinsats. Medianförändringen i vikt var 10% under utgångsvärdet. The study assessed body composition, faecal microbial populations, and blood markers rather than breast cancer incidence or recurrence. Among women who lost at least 10% of their weight, the omega-3 group had the largest fall in the Firmicutes:Bacteroidetes ratio and favourable changes in systemic biomarkers. The omega-3 group also showed increased proportional abundance of the short-chain-fatty-acid-producing microbes Phocaeicola vulgatus and Alistipes putredinis. Those changes correlated with bioavailable estradiol, adiponectin:leptin ratio, and C-reactive protein. Plasma propionate increased by percentage change, while butyrate decreased. Correlation does not establish that the microbial shifts caused the biomarker changes, and the abstract gives no arm-specific effect sizes or p-values. Omega-3 was added to weight loss, so the study cannot separate its contribution from weight reduction and related behavioural changes. It is a small, short-term biomarker study in a selected population, not evidence that omega-3 prevents breast cancer or extends life.

High-dose omega-3 added to behavioural weight loss promoted gut-microbiome shifts associated with improved breast-cancer-risk biomarkers.