Sugar Substitutes Increase Release of GLP-1

It's unknown whether this means anything for people's health, but "in light of the large number of individuals using artificial sweeteners on a daily basis, it appears essential to carefully investigate the associated effects on metabolism and weight," conclude Dr. Rebecca J. Brown and colleagues from the National Institute of Diabetes and Digestive and Kidney Diseases.

Because artificial sweeteners are virtually carbohydrate-free, they have been thought not to have any effect on how the body handles glucose (sugar), the researchers explain.

But there's some evidence that artificial sweeteners may trigger secretion of glucagon-like peptide-1 (GLP-1). GLP-1 is released from the digestive tract when a person eats as a "fullness" signal to the brain, curbing appetite and calorie intake.

To investigate further, Brown's team had 22 healthy normal-weight young people take two glucose challenge tests. These tests, which measure how well the body metabolizes glucose, require a person to drink a sugar-filled beverage after fasting for several hours.

Ten minutes before consuming the "glucose load," study participants drank either roughly two-thirds of a diet soda containing an artificial sweetener or the same amount of carbonated water. 

In both cases, the increase in a person's blood glucose was the same. But the researchers did find that people secreted significantly more GLP-1 when they drank diet soda before the glucose challenge compared to when they drank carbonated water. 

Studies in humans and animals have shown that when artificial sweeteners are consumed without carbohydrates they do not trigger GLP-1 secretion. "However, our data demonstrate that artificial sweeteners synergize with glucose to enhance GLP-1 release in healthy volunteers," Brown and colleagues report. 

What this all means to the average diet soda drinker is not known, but the fact that the effect occurred with less than a single can of diet soda suggests it "may be relevant in daily life," the researchers say.

Future research is needed to understand the significance of enhanced GLP-1 secretion for health, they conclude, and studies should be conducted in people with Type 2 diabetes and other abnormalities in metabolism.