What’s the latest in gut microbiota science?

My gut microbiota is unique to me.  With current advances in medicine and nutrition, a transition is taking place from a one-size-fits-all approach towards personalized therapy. Indeed, the close link between host and gut microbiota, as well as with the environment in which those two elements evolve, makes each patient a unique case. Dr. Purna Kashyap exemplified the problem of  the huge variability in patient response to treatments with irritable bowel syndrome, where, for instance, patients with IBS who have symptoms of diarrhea have a very different gut microbiota compared to those who are constipated. Furthermore, every individual’s relapse profile is different.

Managing disorders of gut-brain interaction from the gut.  The gut-brain axis is the two-way link between the gastrointestinal tract and the brain. In fact, chronic  stress can impact the gut microbiota to the point of increasing the likelihood of irritable bowel syndrome and decreased gut microbiota heath in general. Dr. Emeran Mayer’s work focuses on cognitive behavioral therapy, by teaching patients relaxation strategies such as progressive muscle relaxation, controlled breathing and hypnosis to treat irritable bowel syndrome symptoms. 

The gut microbiota dictate the blood glucose levels. As the gut microbiota is part of our system and forms a symbiosis with the host, bacteria will react to food intake, blood glucose level and circadian cycle. In the context of diabetes prevention and treatment, Dr. Purna Kashyap showed that, based on a person’s gut microbiota profile blood glucose levels following food intake can be predicted.

The gut microbiota beat. 

The circadian cycle is what allows us to fall asleep at night and get up in the morning. Stimuli such as light, sun exposure and food intake regulate that cycle. Dr. Dirk Haller and his team showed that  15% of the gut microbiota follows the same rhythm. Furthermore, by studying patients with  type 2 diabetes and their gut microbiota, they found that the gut microbiota of those patients lost its rhythmicity.

It’s never too late to improve your diet  

Your entire environment shapes your gut microbiota.  Studies on identical twins help scientists understand the effect of diet and environment on gut microbiota. Strikingly, there is a wide variation in gut microbiota from person to person and only 37% of the same gut microbes are shared by identical twins still living together, making diet responsible for that variation. The current challenge presented by Dr. Nicola Segata is that there are many ways of analysing the food consumption of individuals: according to food items, food groups, nutrients or dietary patterns. In that regard, Dr. Segata’s team has found a strong association between unhealthy food  (high in sugar and saturated fat) and specific bacteria and obesity, high body mass index and cardiometabolic diseases, while healthy food  (vegetables, non-transformed products) was mostly associated with the beneficial bacteria.

How we cook food has shaped the long relationship between our gut microbes and us.  

Thanks to the high number of studies on the effect of diet on the intestinal microbiota, we know that the gut microbiota is highly malleable. In other words, after only 24 hours of a change in diet, the microbiota will be different. It is also highly resilient, which implies that if changes in diet do not persist, the intestinal microbiota’s composition will return to its original state in less than 24 hours.   Food intake, digestion and gut microbiota are linked and work together. For instance, the body secretes bile acids during digestion to absorb any fat that has been consumed. Dr. Sloan Delvin is interested in how the gut microbiota can assimilate bile acids and change their conformation, as well as their effect on health. Furthermore, by converting those bile acids, some bacteria also have anti-inflammatory and anti-infectious properties.

Dr. Rachel Carmody brought up an interesting point at the summit about how certain foods are better absorbed by the host when eaten cooked than when raw  and that heat inactivation of antimicrobial compounds in food may also play a role in food's impact on gut microbes. Some foods appear to be better digested cooked than raw, which could be explained by the long period during which fire has been part of human evolution. In addition, raw food not absorbed by the host will be fermented by bacteria, which will then bring calories to the host, in what is known as energy return.

With or without fibres. Dr. Gary D. Wu focused on how to reduce symptoms in patients with inflammatory bowel disease using diet. His research team compared three diet options: vegan, omnivorous and exclusive enteral nutrition. A vegan diet seems to reduce symptoms and the duration of flare-ups compared to an omnivorous diet but, interestingly, exclusive enteral nutrition—liquid food containing 0% fiber—is the gold-standard diet for patients with IBD. However, it has been shown that exclusive enteral nutrition slows gut microbiota recovery and alters carbohydrate and amino acid gut metabolites.