Dietary components’ effects on host health are thought to be mediated in part by their specific effects on the gut microbiome. Probiotics and prebiotics are the most studied substrates, whereas little is known about the impact of dietary fats on the gut microbiome in human cohorts.
A new study, led by Dr. Ana M. Valdes from the Faculty of Medicine and Health Sciences at the University of Nottingham in Nottingham (United Kingdom), has found that dietary omega-3 fatty acids correlate with gut microbiome composition in middle-aged and elderly women.
In order to investigate the relationship between omega-3 fatty acid serum levels and intake and gut microbiome composition and diversity, the researchers analysed the faecal microbiota together with circulating levels of fatty acids including docosahexaenoic acid (DHA), total omega-3 fatty acids, linoleic acid, total omega-6 fatty acids, total polyunsaturated fatty acids, monounsaturated fatty acids, total saturated fatty acids and total fatty acids, of 876 middle aged and elderly female twins (mean age: 64.98 years; mean body mass index: 26.35 kg/m2). Estimated food intake of omega-3 fatty acids was also obtained for each participant from food frequency questionnaires (FFQs) -it was found that dietary omega-3 fatty acid intake estimates from FFQs were correlated with serum levels of total omega-3 fatty acids.
Both omega-3 and omega-6 fatty acids correlated significantly with gut microbiome diversity-microbiome diversity was tested by using different diversity measures: Shannon, Chao 1, Simpson, phylogenetic diversity indices and observed species-whereas no associations were found between gut microbiome diversity and circulating levels of saturated fatty acids or monounsaturated fatty acids.
When adjusting for confounders (circulating levels of total omega-3 fatty acids, DHA, total omega-6 fatty acids and dietary fibre intake), both total omega-3 and DHA serum levels remained significantly associated with gut microbiome diversity and hence the researchers focused specifically on serum levels of DHA. Dietary intake of DHA estimated by FFQs also correlated with gut microbiome diversity.
The strongest associations were found between DHA serum levels and operational taxonomic units (OTUs) from the Lachnospiraceae family. A recent randomized crossover clinical study in obese people also found that canola oil (consists of 63% of monounsaturated fats, 9-11% of polyunsaturated omega-3, and 7% of saturated fat) plus DHA led to an enrichment of Lachnospiraceae when compared to a canola oil only group. Due to the fact that a high gut microbiome diversity is related to lower inflammation, these results suggest that omega-3 fatty acids could be related to lower gut inflammation.
Some of the associations between serum levels of DHA and gut microbiome diversity appeared to be mediated by the abundance of the faecal metabolite N-carbamylglutamate (NCG) as several operational taxonomic units whose abundance was related to DHA serum levels were also associated with NCG faecal levels.
In conclusion, these results show an association between omega-3 circulating levels and gut microbiome diversity, particularly with OTUs of the Lachnospiraceae family. Further research in humans is needed to better explore the effect of dietary omega-3 fatty acids on gut microbiome composition and diversity. In future, interventions related to dietary fats could be useful along with probiotics/prebiotics for diseases in which inflammation and gut microbiota dysbiosis are involved.
Menni C, Zierer J, Pallister T, et al. Omega-3 fatty acids correlate with gut microbiome diversity and production of N-carbamylglutamate in middle aged and elderly women. Sci Rep. 2017; 7:11079. doi: 10.1038/s41598-017-10382-2.