The gut microbiota ferments dietary carbohydrates to produce short-chain fatty acids (SCFAs). In patients with type 2 diabetes mellitus (T2DM), there is a decrease in SCFA production and previous studies have shown that a high-fibre diet is beneficial for patients with T2DM. Now, in a new randomized controlled trial, Liping Zhao, Chenhong Zhang, Yongde Peng and colleagues show that in patients with T2DM a high-fibre diet promotes SCFA-producing gut bacteria, which in turn normalizes levels of HbA1c via an increase in the production of glucagon-like peptide 1 (GLP1).
In their study, the researchers assigned 43 patients with T2DM to receive either usual clinical care (patient education and dietary recommendations according to the 2013 Chinese Diabetes Society guidelines for T2DM) or a high-fibre diet based on whole grains, traditional Chinese medicinal foods (such as oats, and white and red beans, which are high in fibre) and prebiotics for 84 days. “We controlled the energy and macronutrient intake between the two groups so that the only dietary difference was the extra amount of diverse fibres in the treatment group,” explains Zhang.
“a high-fibre diet promotes SCFA-producing gut bacteria”
Patients receiving the high-fibre diet had greater reductions in levels of HbA1c and body weight, and better lipid profiles than patients in the control group. A higher proportion of the treatment group achieved adequate glycaemic control (HbA1c < 7%) compared with the control group. The high-fibre diet increased the abundance of diverse fermentable carbohydrates in the gut and selected for a specific group of bacteria that produce acetate and butyrate. The increased levels of acetate and butyrate in the gut stimulated the production of GLP1, which in turn promoted insulin secretion. The high abundance of the SCFA-producing bacteria also reduced pro-inflammatory bacterial growth, which reduced inflammation and increased insulin sensitivity.
“Targeting SCFA-producing gut bacteria with a personalized high-fibre diet would help patients with T2DM normalize HbA1c levels,” concludes Zhang. “We now need to conduct more clinical trials to find the best possible benefits for patients from this new form of nutrition therapy.”
Zhao, L. et al. Gut bacteria selectively promoted by dietary fibers alleviate type 2 diabetes. Science 359, 1151–1156 (2018)
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Leong, I. High-fibre diet beneficial for T2DM. Nat Rev Endocrinol 14, 324 (2018). https://doi.org/10.1038/s41574-018-0004-6
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