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In the news:New Frontiers in Probiotic & Prebiotic Research

Role for ‘Probiotics’ in Metabolic Syndrome?

We’re learning that the gut microbiota seems to affect nearly all aspects of human health – from brain function to the immune system. But we’re only just beginning to understand how differences in the composition of gut bacteria may influence our health. One area of research coming to the forefront is if and how gut bacteria might contribute to obesity.

Evidence linking gut microbiota to obesity comes mostly from animal studies, but a recent pilot study (1) published in the prestigious journal Nature Medicine, suggests that the microbiota-obesity connection could prove to be important in humans too. The study was conducted in adults with metabolic syndrome – a cluster of conditions, which can include hypertension, insulin resistance, high triglycerides, low HDL, and a large waist size.

A research team from Belgium, Finland and the Netherlands randomized 32 overweight or obese volunteers with metabolic syndrome to receive live bacteria, pasteurized bacteria (killed with heat) or placebo. The bacterium tested was Akkermansia muciniphila – a bacterium normally found in the gut, but at lower levels in those with metabolic syndrome and some inflammatory bowel conditions.

At the end of 3 months, insulin sensitivity, total cholesterol levels and biomarkers of inflammation and liver dysfunction were improved in those taking the pasteurized bacteria vs. the participants taking the placebo. That group also experienced slight decreases in body weight, fat mass and waist circumference compared to placebo takers, though the differences failed to achieve statistical significance.

Interestingly, the live bacteria did not appear to produce the same benefits as the pasteurized bacteria. While the overwhelming majority of clinical studies examining the effects of probiotics on health parameters have been performed with viable or live bacteria, a few studies have also found beneficial effects when testing supplemental non-viable bacteria. That seems to be the case in this study as well.

Obviously, these findings must be replicated in larger and longer trials to confirm their validity. But scientists appear to be on the right path to find out whether there’s a role for specific gut bacteria alongside the cornerstones of regular exercise and a healthy diet for fighting obesity and obesity-related conditions.

Be Consistent with Prebiotics for Benefits

Fiber-rich foods in general encourage the growth of healthy microbes. The inulins, in particular, belong to a class of dietary fibers known as fructans. Inulin-type fructans (ITF) resist breakdown by our digestive enzymes and are fermented to produce healthful short chain fatty acids that provide fuel for maintaining the intestinal lining. ITF also selectively stimulate growth of healthful bacteria such as biidobacteria.

In a recent study (2), healthy volunteers were assigned a diet providing ITF-rich vegetables (about 15 grams ITF/day). Food-related behavior, microbiota com-position, and GI symptoms were measured at the start and end of the 2-week intervention, and 3 weeks after they returned to their usual diet.

As expected, the high ITF increased Bifidobaterium genus and decreased levels of unclassified Clostridiales. Oxalobacteraceae (associated with lower risk of kidney stone formation) tended to be reduced as well. The participants showed greater satiety (feeling full), and less desire for sweet, salty and fatty foods. While the volunteers experienced some gas, intestinal comfort overall was improved (related to changes in microbe composition).

An important finding was that the changes in gut microbiota were only temporary, with the bacterial composition returning to pre-trial levels 3 weeks later. This underscores the importance of continuing to eat a fiber rich diet in order to maintain its beneficial effects. Along with eating high-fiber foods in general, sources of ITF include spinach, leeks, wheat, artichoke, onion, banana and garlic.

References

1. Depommier C, et al. Supplementation with Akkermansia municiphila in overweight and obese human volunteers: a proof-of-concept exploratory study. Nat Med. Epub July 1, 2019.
2. Hiel S, et al. Effect of a diet based on inulin-rich vegetables on gut health and nutritional behavior in healthy humans. Am J Clin Nutr. 109:1683-95, 2019.