RT Journal Article SR Electronic T1 A randomised trial of the effect of omega-3 polyunsaturated fatty acid supplements on the human intestinal microbiota JF Gut JO Gut FD BMJ Publishing Group Ltd and British Society of Gastroenterology SP 1974 OP 1983 DO 10.1136/gutjnl-2017-314968 VO 67 IS 11 A1 Henry Watson A1 Suparna Mitra A1 Fiona C Croden A1 Morag Taylor A1 Henry M Wood A1 Sarah L Perry A1 Jade A Spencer A1 Phil Quirke A1 Giles J Toogood A1 Clare L Lawton A1 Louise Dye A1 Paul M Loadman A1 Mark A Hull YR 2018 UL http://gut.bmj.com/content/67/11/1974.abstract AB Objective Omega-3 polyunsaturated fatty acids (PUFAs) have anticolorectal cancer (CRC) activity. The intestinal microbiota has been implicated in colorectal carcinogenesis. Dietary omega-3 PUFAs alter the mouse intestinal microbiome compatible with antineoplastic activity. Therefore, we investigated the effect of omega-3 PUFA supplements on the faecal microbiome in middle-aged, healthy volunteers (n=22).Design A randomised, open-label, cross-over trial of 8 weeks’ treatment with 4 g mixed eicosapentaenoic acid/docosahexaenoic acid in two formulations (soft-gel capsules and Smartfish drinks), separated by a 12-week ‘washout’ period. Faecal samples were collected at five time-points for microbiome analysis by 16S ribosomal RNA PCR and Illumina MiSeq sequencing. Red blood cell (RBC) fatty acid analysis was performed by liquid chromatography tandem mass spectrometry.Results Both omega-3 PUFA formulations induced similar changes in RBC fatty acid content, except that drinks were associated with a larger, and more prolonged, decrease in omega-6 PUFA arachidonic acid than the capsule intervention (p=0.02). There were no significant changes in α or β diversity, or phyla composition, associated with omega-3 PUFA supplementation. However, a reversible increased abundance of several genera, including Bifidobacterium, Roseburia and Lactobacillus was observed with one or both omega-3 PUFA interventions. Microbiome changes did not correlate with RBC omega-3 PUFA incorporation or development of omega-3 PUFA-induced diarrhoea. There were no treatment order effects.Conclusion Omega-3 PUFA supplementation induces a reversible increase in several short-chain fatty acid-producing bacteria, independently of the method of administration. There is no simple relationship between the intestinal microbiome and systemic omega-3 PUFA exposure.Trial registration number ISRCTN18662143.