Artificial Sweeteners Have Little or No Benefit to Health, Researchers Conclude

A woman puts artificial sweetener in her coffee.
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Two-thirds of Americans are overweight, and those who diet sometimes turn to alternative sweeteners — including aspartame, sucralose and stevioside — to cut calories.

Now, a new review of many studies suggests that doing so might not be the best idea.

The scientists took a comprehensive look at more than 11,000 studies and found that, for overweight individuals or those with high blood pressure (hypertension) or diabetes, the benefits of consuming zero-calorie, "non-nutritive sweeteners" were modest to nil. For other people, there was an increased risk of weight gain, type 2 diabetes, hypertension, stroke and heart disease. [7 Biggest Diet Myths]

"Overall, the evidence does not support the intended purpose of weight loss and suggests that there might be adverse effects in the long term," said Meghan Azad, lead author of the review and an assistant professor at the University of Manitoba.

Previous research had suggested that non-nutritive sweeteners were not the healthiest choice, but those studies were smaller in scope than the new review, and tended to focus on one outcome at a time, said Azad, who researches the development of chronic diseases.

"They would look only at weight gain, or only at diabetes," Azad told Live Science. "But we wanted to be really comprehensive and look at the whole panel of cardio-metabolic diseases."

To do so, Azad and her team screened 11,774 published papers, looking for studies that specifically evaluated the consumption of non-nutritive sweeteners in people ages 12 and older. Some of the studies that the researchers looked at were randomized controlled trials, which are the strongest type of scientific evidence. In the trials, half of the participants were asked to consume the alternative sweeteners and the other half were asked not to, and the scientists looked for differences between the groups. The researchers also looked at observational studies, where patients were asked if they used non-nutritive sweeteners.

Artificial sweeteners and body mass index

The team was primarily interested in how the sweeteners might be linked with people's body mass index, the measure of body fat based on weight in relation to height. But they were also interested in studies that reported on weight gain, obesity, glucose metabolism, type 2 diabetes, hypertension and other heart- and kidney-related outcomes.

Based on these criteria, the researchers narrowed the number of published papers down to 37. Seven of these were randomized controlled trials lasting at least six months that followed a total of 1,003 people. The participants were overweight or had hypertension or diabetes at the start of the studies, and during the studies, they used the alternative sweeteners as part of a weight-loss plan. [Diet and Weight Loss: The Best Ways to Eat]

The other 30 studies were observational studies of people from the general population who were not necessarily overweight. Although the direct goal of these studies was not to specifically track the effects of non-nutritive sweeteners, the participants were asked about their consumption of sweet substitutes. For these studies, a total of more than 405,000 participants were followed over the course of at least 10 years.

After the researchers analyzed all of the study results, they concluded that non-nutritive sweeteners did not substantially help people and, in many cases, may have harmed them.

In the seven randomized controlled trials, for example, some participants lost weight, but others had no significant weight loss over the six-month period. In the 30 observational studies, the researchers found a link between consuming artificial sweeteners and higher risks of gaining weight, becoming obese, and developing high blood pressure, diabetes, heart disease and other health issues, the scientists reported.

Because some of the people in the studies may have benefited from the sweeteners — particularly those in the randomized controlled trials — while others saw adverse health outcomes, scientists need to look more closely at the use of these products, said Allison Sylvetsky-Meni, an assistant professor of exercise and nutrition sciences at The George Washington University who was not involved with the new review of studies.

"I don't think that they [non-nutritive sweeteners] are necessarily something people should be cautioned against, but they're also, I don't think, something that people should be encouraged [to consume] for weight loss," Sylvetsky told Live Science. "We need to learn more about how they're working, what they're doing and how they affect different populations, if at all," she said. [Special Report: The Science of Weight Loss]

The role of gut bacteria

Azad noted that the new review was a part of a larger effort to determine the effects of non-nutritive sweeteners on the gut microbiome (bacteria and other microbes in the gut) and cardio-metabolic health.

Studies have shown that the makeup of gut bacteria is less diverse in obese people than in people of a healthy weight, Azad said. Because the gut microbiome plays a big role in extracting energy from food and even in producing vitamins, a less-diverse population might contribute to weight gain, she said.

A study Azad and her team published earlier in the year in the journal JAMA Pediatrics showed that babies born from mothers who consumed artificial sweeteners were more likely to be overweight by the time they were 1 year old. Whether there is a direct link is not known. But one of her next research projects is to analyze the gut microbiomes of babies whose mothers have consumed artificial sweeteners.

"In recent surveys from the United States, over 50 percent of adults are reporting that they consume these products on a daily basis," Azad said. "There is just not a lot evidence out there for what the long-term impact might be."

Originally published on Live Science.

Tracy Staedter
Live Science Contributor
Tracy Staedter is a science journalist with more than 20 years of experience. She has worked as an editor for Seeker, Discovery, MIT Technology Review, Scientific American Explorations, Astronomy and Earth and authored the children’s science book, Rocks and Minerals, part of the Reader’s Digest Pathfinders series. In 2013, she founded the Boston-based writing workshop Fresh Pond Writers.