People hoping to lose a few pounds by substituting artificial sweeteners for regular sugar may end up disappointed, suggests a fresh look at past research.
The review of 37 studies suggests the use of so-called non-nutritive sweeteners could be linked to weight gain and other undesirable outcomes like high blood pressure and type 2 diabetes.
"From all that research, there was no consistent evidence of a long term benefit from the sweetener, but there was evidence for weight gain and increased risks of other cardiometabolic outcomes," said lead author Meghan Azad, of the University of Manitoba in Winnipeg, Canada.
Artificial sweeteners like aspartame, sucralose and stevioside are growing increasingly popular as evidence mounts that sugar is fueling the obesity epidemic, Azad and colleagues write in CMAJ.
The artificial sweeteners are chemically different than sugar. They activate receptors on the tongue that lets the brain know the person is eating or drinking something sweet.
Past research on these sweeteners shows a mixed bag of results, including links to weight gain, as well as links to weight loss, according to the authors of the new review.
For the analysis, they looked through the medical literature for studies examining possible links between artificial sweeteners and weight or health issues like obesity.
The researchers found seven randomized controlled trials, which are considered the gold-standard of medical research. Some of the trials, for example, compared people who drank artificially sweetened beverages to people who drank water. The researchers also found 30 studies that followed people using the sweeteners over time.
They found no link between the use of artificial sweeteners and changes in body mass index (BMI), which is a measure of weight in relation to height, among the 1,003 people in the randomized controlled trials. They also didn't find a link between the sweeteners and other outcomes.
Among the 405,907 people included in the 30 other studies, the researchers found that artificial sweeteners were tied to a small increase in BMI, weight, waist size, obesity, high blood pressure, heart problems and metabolic syndrome.
"I think it's cause for some caution and rethinking whether or not these products are without any effect," Azad told Reuters Health.
The researchers caution, however, that the studies that followed people over time may be biased since artificial sweeteners are promoted as a treatment for conditions like obesity or diabetes. Also, the randomized controlled trials were relatively short.
Azad also said they were not able to look at individual sweeteners.
"It's possible that different sweeteners have different effects, but we were not able to examine that because of the studies available," she said.
The risks and benefits of these sweeteners need to be evaluated, but the science examining those benefits is lacking, said Sai Das of the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston, who was not involved with the new study.
"It is time for the science to look at what - if any - benefits there are to see if that is meaningful enough to outweigh the risks that have been highlighted," Das told Reuters Health.
Until there is better research, Das said, people should use be cautious about using artificial sweeteners.