"Given the widespread and increasing use of artificial sweeteners, and the current epidemic of obesity and related diseases, more research is needed to determine the long-term risks and benefits of these products", she added.
"There's no clear evidence for benefit from the artificial sweeteners, and there is a potential that they have a negative impact, but we need more research to figure it out for sure", said Meghan Azad, an epidemiologist at the University of Manitoba and lead author on the paper.
"Despite the fact that millions of individuals routinely consume artificial sweeteners, relatively few patients have been included in clinical trials of these products", said author Dr. Ryan Zarychanski in a news release.
The clinical trials (which tended to be small, short, and focused on people who were obese and using low-calorie sweeteners in an effort to lose weight) failed to show a consistent link between low-calorie sweetener consumption and weight loss metrics such as body mass index (BMI), waist circumference, or pounds lost.
The Canadian team looked at 37 studies involving more than 400,000 people over an average of ten years.
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Other data suggests that people who regularly take sweeteners like aspartame and sucralose are more likely to develop health problems in the future.
According to Dr. Azad, until the characterization of the long-term health effects - both risks and benefits - of artificial sweeteners are completed caution is necessary. Her own work on animals has shown these sweeteners can alter the composition of gut microbiota, which she says could play a role in long-term changes in metabolism.
Azad suggests that consumers who turn to artificial sweeteners on the assumption that they're a healthier choice should to be cautious. "They're shifting calories to other foods", Azad explained. Seven of the studies were randomized controlled trials, a type considered to be the gold standard in scientific research.
Many people use artificial sweeteners. She said the studies may have neglected other things that influence weight, such as exercise or overall diet.
"However, consumption of non-nutritive sweeteners has been paradoxically associated with weight gain and incident obesity". Jane Shearer, an associate professor of kinesiology at the University of Calgary who is studying these sweeteners, notes the number of products that contain sugar substitutes has grown significantly in Canada in the past five years, with energy drinks, no-sugar-added ice creams, yogurt and even some bread products.
Another possibility, Azad said, is that we compensate and think that drinking a diet pop permits us to enjoy pizza and cake later. Observational studies, which are a lot longer in duration can do that much better but the drawback is that they only find associations and not causation.