I was introduced to a new probiotic species this morning that sound like it holds a lot of promise: Roseburia intestinalis. I came across an article[i] on Gut Microbiota for Health describing research into the beneficial effects of butyrate-producing bacteria on atherosclerotic plaques and type 2 diabetes. Butyrate, if you remember, is a short-chain fatty acid, a metabolite of beneficial gut bacteria, that is highly anti-inflammatory.
The research, out of the University of Wisconsin-Madison, was an attempt to figure out exactly how butyrate-producing bacteria produced their beneficial effects. Using mice, the scientists tested out 8 different human gut bacteria, with or without R.intestinalis. They found that the R.intestinalis, which was already known to be a butyrate-producing species, “…showed the strongest negative correlation with atherosclerotic lesion size.”
This is where it gets super interesting. When the mice were fed a diet high in plant polysaccharides (beneficial prebiotics), along with R.intestinalis and other bacteria that were poor butyrate producers, they still had a 4-fold increase in butyrate levels and reduced atherosclerotic plaques. HOWEVER: when mice were given the same bacterial species (including R.intestinalis) but a diet low in plant polysaccharides, this beneficial effect was not seen! “These results show that diet is crucial to the athero-protective effects of R. intestinalis…”
This is a possible explanation as to why – even with the best gut bacteria in the world – a diet high in plant fiber is preventative: “…butyrate-producing gut microbes might be relevant mediators involved in explaining the benefits of dietary fiber for better cardiometabolic health. It should be kept in mind that butyrate protective effects are dictated by diet, which highlights the fact that commensal gut microbes are neither good nor bad per se, and that context (diet and epigenetic changes in this study) also matters.”
But wait, there’s more! The researchers discovered too that butyrate production via R.intestinalis is also associated with an improvement in gut barrier function (i.e. tightening of the cell junctions), so good for leaky gut.
Now my interest was really peaked so I did some snooping around and learned that R.intestinalis is known to be decreased in patients with inflammatory bowel disease. Research published this past year[ii] showed that this species lowered pro-inflammatory cytokines and raised regulatory cytokines (those which turn off the inflammatory response). The data was so strong from this study, in fact, that the researchers state flat out that R.intestinalis may be of potential use in the treatment of IBD.
Well, this is all really promising. Unfortunately, the species is not available yet in a commercial probiotic form. So I looked around to see if there are any specific dietary interventions that are known to increase levels.
A November 2018 human (randomized, open-label, cross-over, 8 week long) trial, published in the eminent journal, Gut,[iii] showed that omega 3 fatty acids are associated with an increase in Bifidobacterium, Roseburia and Lactobacillus. (You do have to wonder if some of the anti-inflammatory effects of omega 3s is not actually due to beneficial microbiome alterations. ???)
These results were completely in line with a study[iv] completed the year before on rats, wherein the animals were fed one of two diets, one with walnuts (which are high in omega 3s) and one with a replacement that contained the same amount of fat, fiber and protein in walnuts, but which lacked the omega 3 component: “Walnuts enriched the microbiota for probiotic-type bacteria including Lactobacillus, Runinococcaceae, and Rosburia…Walnut consumption altered the gut microbial community suggesting a new mechanism by which walnuts may confer their beneficial health effects.”
So, for the moment, we are reliant upon adding plenty of plant fibers, omega 3s and walnuts to our diets….which should come as no surprise to my regular readers ‘cause how many times do I have say, “I told you so”?! 🙂 I will certainly continue to look for more research on this as it becomes available.
[ii] Zhu, C, et. al. Roseburia intestinalis inhibits interleukin-17 excretion and promotes regulatory T cells differentiation in colitis. Molecular Medicine Reports. 2018:17(6):7567-7574. 10.3892/mmr.2018.8833
[iii] Watson, H, et. al. A randomized trial of the effect of omega-3 polyunsaturated fatty acid supplements on the human intestinal microbiota. Gut. 2018:67(11):1974-1983. doi: 10.1136/gutjnl-2017-314968
[iv] Byerley, LO, et. al. Changes in the gut microbial communities following addition of walnuts to the diet. The Journal of Nutritional Biochemistry. 2017:48:94-102. https://doi.org/10.1016/j.jnutbio.2017.07.001