Hana Kahleova, MD: Gut Microbiota Changes from Plant-Based Diet

So, we’ve known for quite a long time
that plant-based diets work well for for the treatment of diabetes and also
for diabetes prevention, however we wanted to look into the mechanisms
behind the beneficial effects of plant-based diets and gut bacteria
is an emerging area of research connecting the dots between inflammation,
insulin resistance, fatty liver disease, and also diabetes. So, we decided to look
into the gut microbiome composition in people who were overweight and were
insulin resistant, but who had not had diabetes yet. So, we looked at their gut
microbiome composition at baseline and then we randomized them to follow a
vegan diet — a plant-based diet — or to stay on their usual diet for 16 weeks
to account for seasonal fluctuations and stuff like that and we had 147
participants that were randomized in this clinical trial and, as expected, all
the metabolic outcomes improved in the vegan diet. So, people
were losing weight — 5.8 kilograms on average over the course of 16 weeks — and
two-thirds of the weight loss was due to fat loss. We were measuring the body
composition using a DEXA scan and people were losing visceral fat and were
improving their insulin sensitivity and these metabolic outcomes were also
related to the changes in gut microbiome. More specifically, we found out that the
whole family of bacteroidetes increased in response to the vegan diet and, more
specifically, the short chain fatty acid producing bacteria like cyclic bacteria
prowazekii increased, which was a super positive finding because
decreased amounts of Faecalibacterium prausnitzii have been found in patients
with type 2 diabetes and have been also associated with increased inflammation
and increased insulin resistance. So, increasing of faecalibacterium prausnitzii is one of the short chain fatty
acid producing bacteria is a very positive finding and, more importantly,
these changes in faecalibacterium prausnitzii were also associated with the
positive metabolic outcomes, with the weight loss, and loss in fat mass and
loss in visceral fat. Another bacteria that played a role in switching to the
vegan diet was bacteroides fragilis which decreased in both groups however
it decreased less on the vegan diet so the treatment effect was positive and
these change the changes in bacteroides fragilis were also related to changes in
weight loss and also changes in fat mass and insulin sensitivity.
Our study
highlights the importance of fiber, fiber intake for the prevention of diabetes
because these short chain fatty acid producing bacteria feed on fiber and
produce the short chain fatty acids that have positive metabolic benefits. That’s
why it’s important for people who are at risk of developing diabetes to consume
high amounts of fiber. So, unprocessed plant foods are rich in fiber and should
their consumption should be encouraged.

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