If zero-calorie sweeteners sound too good to be true, they just might be.
A growing body of evidence links non-nutritive sweeteners to weight gain and other negative health effects, as scientists evaluate the long-term impact of routine consumption of zero-calorie sugar substitutes.
Several health-focused groups have recommended non-nutritive sweeteners — such as aspartame, sucralose or stevioside — as guilt-free substitutes for sugar to help limit calories, aid weight loss and manage diabetes.
But a study published Monday in the Canadian Medical Association Journal found that long-term consumption of these sweeteners may contribute to modest weight gain, increased waist circumference, higher incidences of obesity and metabolic syndrome — a variety of conditions that increase the risk of heart disease, diabetes and stroke.
Furthermore, researchers found in an analysis of short-term, randomized clinical trials that sweeteners had no significant impact on body mass index.
“It was kind of surprising that looking at all the evidence out there there was no clear benefit of these artificial sweeteners, yet there was evidence for harmful effects in the long-term consumption,” said Meghan Azad, lead author of the study and a research scientist at the University of Manitoba.
Ms. Azad and a team of researchers with the University of Manitoba’s George and Fay Yee Center for Healthcare Innovation conducted a “study of studies,” evaluating results from randomized clinical trials and long-term follow-up cohort studies.
In an analysis of seven randomized clinical trials, which followed about 1,000 participants for periods from six to 24 months, Ms. Azad and her team found inconsistent results on consumption of sweeteners and decreases in weight, body mass index or weight circumference.
They compared their findings with 30 long-term, observational studies that followed more than 400,000 participants for periods of 10 to 30 years. Results from those studies found participants had increased risks of weight gain and diabetes, but researchers could observe only an association, not a direct cause-and-effect relationship.
“The big message is that we don’t know a lot, and we need more research,” Ms. Azad said. “But I think, for the average person, including myself, it is surprising that you see links between the artificial sweeteners and increased weight gain and increased diabetes, because those are the exact things people are trying to avoid by taking them in many cases.”
Consumption of artificial sweeteners is pervasive in the U.S. and expected to continue to rise, with about 25 percent of children and more than 40 percent of adults reporting consuming low-calorie sweeteners, according to a study this year published in the Journal of the Academy of Nutrition and Dietetics.
A number of popular sweeteners are either approved by the Food and Drug Administration for consumption or generally regarded as safe, and their non-nutritive quality is supposed to mean that it passes through the body.
However, researchers are continuing to evaluate the interaction between the sweeteners and our bodies — whether the sweeteners have an effect on gut bacteria or can change the metabolism.
Of the evaluated observational studies, Ms. Azad said that data included controls for participants’ overall diet quality and intake of calories to help account for any factors that would also be responsible for increased weight gain or instances of diabetes. But even with the controls, an association was found between consumption of sweeteners and negative health effects.
“So that would suggest that it’s something more biological about the sweeteners themselves. But again, we have to be careful with these types of studies that find associations and really can’t prove cause and effect,” Ms. Azad said.
For herself, Ms. Azad said, she has stopped using sweeteners in her coffee and now chooses sparkling water with lime instead of diet soda.
“I’m a scientist who likes math and numbers, and to me it was sort of a clear comparison: 100 calories versus zero calories. But the research is showing it’s more than just the number of calories and the other effects it might be having,” the researcher said.
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