The Israeli scientists, whose findings were released Wednesday by the respected journal Nature, are calling for a reassessment of use of artificial sweeteners, one of the most widely used food additives in the world.
While some observers are harshly critical of the study, others say the findings are enough to make them swear off the sweeteners.
“I’m looking at this thinking I’m never drinking a diet soda again,” microbiologist Emma Allen-Vercoe, at the University of Guelph, told Postmedia News after reviewing the study.
Not only did the study find artificial sweeteners can raise blood sugar levels but it indicates they do so by altering the microbiota, the elaborate ecosystem of bacteria and microorganisms living in the gut.
“What really struck me was that the effect on the microbiota was so extreme,” says Allen-Vercoe, who specializes in the gut ecosystem and the important role it plays in keeping people healthy. “It’s a pretty impressive piece of work.”
Not everyone agrees. Berna Magnuson, a toxicologist and nutritionist who consults for the soft drink industry and teaches part time at the University of Toronto, takes issue with the study’s “broad sweeping” conclusions saying they are not substantiated by the experiments, most of which entailed feeding high levels of saccharin to mice. One of the human experiments involved just seven people.
“I don’t believe it means anything in terms of public health,” says Magnuson, noting that previous studies have shown artificial sweeteners can help people lose weight.
The Israeli team say their results are “preliminary.” But the findings raise enough red flags to “prompt additional debate and study and examination of what is currently a massive use of the artificial sweeteners,” co-author Eran Segal, of the Weizmann Institute of Science, told a media briefing.
Health Canada, which regulates use of the compounds widely marketed as a way to lose weight and control diabetes, says it has not yet had a chance to review the findings.
The Israeli team fed saccharin, sucralose and aspartame to mice and found the sweeteners altered the animals’ metabolism and raised blood sugar levels.
To explore what was happening they then fed mice saccharin and found a shift in gut bacteria was involved in elevating the blood sugars. In one experiment they transplanted feces from the saccharin-fed mice to germ-free mice, which had no gut bacteria of their own. The transfer elevated blood-sugar levels in the transplanted mice.
Segal says consuming sweeteners appears to favour the growth of gut microbes that break down sugary products in a more efficient way and “enhance energy harvest.”
For the human component of the study, the researchers looked at 381 people involved in an ongoing nutritional study and found many of the individuals consuming artificial sweeteners also had elevated glucose levels and shifts in gut bacteria.
Next, seven human volunteers who did not normally consume sweeteners were put on a diet that included the maximum daily intake of saccharin allowed by health authorities — the equivalent of about 40 cans a day of a artificially sweetened cola-type drink.
Within a week four the volunteers developed elevated blood-glucose levels and altered gut bacterial communities similar to those seen in the saccharin-fed mice. Transfer of feces from the affected individuals into germ-free mice, induced elevated blood sugar levels in the mice, which had never consumed artificial sweeteners.
Allen-Vercoe says the work points to the “very slow dawning that we are missing a threat by not looking at what the microbiota is doing.”
There is a need to reassess not just artificial sweeteners but many commonly used chemicals and medicines to see what impact they are having on microbes living on and in our bodies, says Allen-Vercoe, who is not the only one ready to give up sweeteners.
The study’s lead author Eran Elinav at the Weizmann institute says the findings prompted him to stop consuming caffeinated drinks with artificial sweeteners.