New research presented at this year's annual meeting of the European Association for the Study of Diabetes (EASD) reveals that consumption of low-calorie sweeteners (LCS) can change the types of bacteria found in the gut, in association with impaired regulation of glucose levels.
The research was conducted by Associate Professor Richard Young and colleagues from Adelaide Medical School and the Centre of Research Excellence in Translating Nutritional Science to Good Health, University of Adelaide, Australia, together with researchers from the South Australian Health & Medical Research Institute, Adelaide, and Flinders University South Australia. The study looked at the effects of LCS on gut microbes and how the body absorbs and regulates glucose.
Previous studies of disease origins indicate that a regular high intake of beverages sweetened with LCS is linked to an increased risk of developing type 2 diabetes (T2D), but the underlying mechanism of how this happens is unknown. The authors had recently showed that adding LCS to the diets of healthy non-diabetic subjects for two weeks was enough to cause a clinically relevant increase in how their bodies responded to the consumption of glucose. It remains unclear, however, whether gut dysbiosis (a change in the balance of bacteria) also contributes to the observed abnormalities in blood glucose levels, as has been observed in studies on rodents.
A group of 29 non-diabetic subjects with an average age of 30 years and average body mass index of 24 kg/m2 were recruited for the study. Fifteen participants were randomised to consume a placebo, while 14 consumed an LCS combination (92mg sucralose and 52mg acesulfame-K) equivalent to drinking around 1.5 litres of diet beverage per day. The dose was administered in the form of capsules which were taken 3 times per day over a 2-week period. Stool samples were taken before and after LCS treatment to determine the types and species of microorganisms present.
The study found that LCS-treated individuals exhibited a greater variation in the types of microbes present in their faeces along with a significant reduction in the good-health-associated bacterium Eubacterium cylindroides. Populations of beneficial bacterial species which help to ferment food also decreased, while there was a rise in the abundance of 11 opportunistic gut bacteria.
In addition, the team observed a decrease in the population of Butyrivibrio bacteria that was correlated with a drop in the release of the hormone GLP-1, which helps to control blood glucose levels. Finally, there were changes in the abundance of microbial genes involved in the metabolism of simple sugars like sucrose and glucose.
The authors say: "In healthy non-diabetic subjects, two weeks of low-calorie sweetener supplementation was sufficient to disrupt gut bacteria and increase the abundance of those which are normally absent in healthy individuals. The observed decrease in fermentative bacteria populations and changes in the pathways used by bacteria to harvest energy predicted a deterioration in the body's ability to regulate glucose."
They conclude: "Our findings support the concept that such sweeteners worsen blood sugar control in healthy subjects by disrupting the regulation of glucose uptake and disposal, as well as from changes in the balance of gut bacteria. This highlights the clinical relevance of dietary low-calorie sweetener patterns to overall blood sugar control."
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