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.”
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