On the surface, artificial sweeteners appear to offer a free ride — sugary-sweetness without calories. In fact, it has long been thought that artificial sweeteners don't have an effect on metabolism. But new research on sucralose (Splenda) has found that the sweetener can raise blood sugar and insulin levels, and lower insulin sensitivity.
In most studies of artificial sweeteners in humans, the sweetener is given alone. But that's not how sweeteners are used in real life: people add them to their coffee or put them on cereal or some other food. And most researchers have chosen lean, healthy people as subjects.
A recent Washington University School of Medicine study took a more realistic look at the effects of sweeteners. Its subjects were obese people (average BMI of 42), and it tested the effects of sucralose followed by consumption of glucose, the body's main fuel.
At least one sweetener has metabolic effects, at least on obese people, the very group that is most often encouraged to consume artificial sweeteners to help them lose weight.
When people drank the sucralose, their blood sugar peaked about 17% higher than when they drank water. Insulin secretion was 20% higher and insulin sensitivity decreased by 23%.
The elevated insulin response might be good because it means the person responds to sugar spikes with additional insulin. But lowered insulin sensitivity is probably bad because insulin resistance is often a step down the road towards diabetes.
What the study does show is that one sweetener has metabolic effects, at least on obese people, the very group that is most often encouraged to consume artificial sweeteners to help them lose weight.
It's not known if thinner individuals would experience these changes. It's also not clear whether the metabolic changes, such as a 20% increase in insulin secretion, are clinically significant or not. It will take more research to answer these questions.
The study is published online before print in Diabetes Care and will also appear in a future print issue of the journal.