Arecent study from Columbia University Irving Medical Centre in the US, found that dietary sugar alters the gut microbiome, which can lead to metabolic disease, pre-diabetes, and weight gain.

The findings, published in the research publication Cell, suggest that diet matters, but an optimal microbiome is important for the prevention of metabolic syndrome, diabetes and obesity.

Dietary research
Although we’re aware that a high-sugar Western diet can lead to obesity, metabolic syndrome, and diabetes, it was not clear how this type of diet kickstarts unhealthy changes in the body.

This led to an investigation by Ivalyo Ivanov PhD, associate professor of microbiology and immunology at Columbia University Vagelos College of Physicians and Surgeons, and his colleagues, into the initial effects a Western-style diet had on the microbiome of mice.

After four weeks on the diet, characteristics of metabolic syndrome, such as weight gain, insulin resistance, and glucose intolerance began to emerge and the microbiomes had changed dramatically, with the amount of segmented filamentous bacteria falling sharply and other bacteria increasing in abundance.

This reduction in filamentous bacteria, the researchers found, was critical to health through its effect on Th17 immune cells. The drop in filamentous bacteria reduced the number of Th17 cells in the gut, and further tests revealed that these cells are necessary to prevent metabolic disease, diabetes, and weight gain.

“These immune cells produce molecules that slow down the absorption of ‘bad’ lipids from the intestines and they decrease intestinal inflammation, so they keep the gut healthy and protect the body from absorbing pathogenic lipids” Ivanov says.

Sugar vs fat
When looking at what component of the high-fat, high-sugar diet led to these changes, Ivanov’s team found that sugar was to blame.

“Sugar eliminates the filamentous bacteria, and the protective Th17 cells disappear as a consequence,” says Ivanov. “When we used a sugar-free, high-fat diet, the intestinal Th17 cells were retained, offering protection from obesity and pre-diabetes, even though the same number of calories were consumed.”

However, eliminating sugar did not help in all cases. Where filamentous bacteria were missing to begin with, the elimination of sugar did not have a beneficial effect and obesity and diabetes developed.

“Our study suggests that for optimal health it is important not only to modify your diet but also improve your microbiome or intestinal immune system, for example, by increasing Th17 cell-inducing bacteria,” said the researchers.