Artificial sweeteners may not be the healthy sugar alternative some herald them to be.
Research out of the University of Manitoba found long-term use of the sweeteners, such as aspartame, sucralose and stevia, may be associated with weight gain, Type 2 diabetes, and high blood pressure.
"I was one of the people that put Splenda in my coffee everyday and thought it was a great choice, and I'm rethinking that decision," said the study's lead author, Meghan Azad. She hasn't used the sweetener since finishing the study.
Researchers looked at 37 studies of more than 400,000 people and analyzed the trends across them. What emerged was a contradiction of public perception — sweeteners many use to lose weight may actually be expanding their waistline.
Azad said there are a few theories that could explain that. One pertains to gut bacteria, which helps humans extract calories from food. Depending on the mix of their bacteria, people get different amounts of energy from the same food, and this bacteria is altered by sweeteners.
Another theory is artificial sugar triggers the body's metabolism through its sweet taste even though there are no calories to metabolize. If this becomes a pattern, the body may reprogram its metabolism in a way that encourages weight gain.
Given the choice between sugar and artificial sweetener, Azad said people should choose neither.
"You could choose water, or black coffee," she said.
With the prevalence of anti-sugar campaigns, Azad said more research needs to be done on sugar's substitute.
"We don't want to shift people from one bad thing to another bad thing," she said.
Canada doesn't have statistics on sweetener consumption, but Azad estimates it's similar to the United States, where about 40 per cent of adults use artificial sweetener daily. Azad said this number is likely low because it's self-reported.
"Some people are probably consuming them without knowing it," she said, noting artificial sweeteners are in some foods people wouldn't expect, such as salad dressings and yogurts.
Health Canada has approved several sugar substitutes as safe if they're not consumed in bulk. They include sucralose (Splenda), aspartame (Equal), acesulfame-potassium (Equal), polydextrose, saccharin (Sweet'N Low), and stevia.
The organization said the acceptable daily intake for aspartame is 40 milligrams per kilogram of body weight. For example, a person weighing 140 pounds (about 64 kilograms) could have about 2,560 mg of aspartame a day. One can of Diet Coke has about 125 mg of aspartame.
As sweeteners become more pervasive, they're found in products many don't associate with artificial sugar, such as some sports drinks, fruit juices, and flavoured water.
Studies on rats once linked sweeteners with cancer, but research on sweeteners in humans haven't shown the same association.
The link between artificial sweeteners and cardiometabolic diseases such as diabetes and heart disease has not been proved by experimental studies. Azad and her colleagues are calling for further research into the topic.
The Canadian Beverage Association released a statement questioning the validity of Azad's findings.
"The study itself provides conflicting evidence... In fact, there is a substantial body of evidence from other researchers that low-calorie sweeteners are an effective tool to help people lose and manage weight," it states.
Azad and her team noted the limitations of the research in their paper, saying many of the randomized controlled trials (a type of scientific experiment) they looked at were at high risk of bias.
"We need a lot more research before we draw firm conclusions," she said. She hopes the study sends a message to scientists and research funders to focus more on this area of public health.