If you've been startled by recent health warnings and have ditched that sugar in your coffee for a couple of sweeteners instead, then you might want to take a look at this new study, which suggests that sugar-free sweeteners could actually increase your glucose intolerance and diabetes-risk by affecting bacteria in the gut.
From improving metabolism and helping people to slim, widespread use of artificial sweeteners may be fuelling the obesity and diabetes epidemic.
Scientists found that giving mice water laced with three commonly used artificial sweeteners in doses equivalent to those recommended for humans caused them to develop glucose intolerance.
The condition occurs when sugar levels in the blood rise and can lead to Type-2 diabetes, which affects around 2.7 million people in the UK.
Tests showed that in mice, sweeteners altered the balance of gut microbes that have been linked to susceptibility to metabolic diseases.
They also affected the composition and function of gut bacteria in a small number of human volunteers, resulting in glucose intolerance after one week.
Lead researcher Dr Eran Elinav, from the Weizmann Institute in Rehovot, Israel, said: "Our relationship with our own individual mix of gut bacteria is a huge factor in determining how the food we eat affects us.
"Especially intriguing is the link between use of artificial sweeteners - through the bacteria in our guts - to a tendency to develop the very disorders they were designed to prevent.
"This calls for reassessment of today's massive, unsupervised consumption of these substances."
The study, reported in the journal Nature, found that people's reaction to artificial sweeteners varied depending on the kind of bacteria they harboured.
Two different populations of human gut microbes were identified, one that induced glucose intolerance when exposed to the sweeteners and another that did not.
Certain bacteria reacted to artificial sweeteners by secreting substances that provoked an inflammatory response similar to a sugar overdose, the scientists believe.
Co-author Professor Eran Segal, also from the Weizmann Institute, said: "The results of our experiments highlight the importance of personalised medicine and nutrition to our overall health.
"We believe that an integrated analysis of individualised 'big data' from our genome, microbiome and dietary habits could transform our ability to understand how foods and nutritional supplements affect a person's health and risk of disease."
British experts said the findings were interesting but urged caution.
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Dr Katarina Kos, senior lecturer and consultant in diabetes and endocrinology at the University of Exeter, said: "The study is based primarily on mouse experiments and only seven human subjects were studied.
"The findings require further confirmation prior to making firm conclusions. Larger scale human studies... are urgently required.
"These findings support the widespread understanding that water is the healthiest drink option and that we should avoid sweet and sweetened drinks. Water is the best drink to control our blood sugar."
Sir Stephen O'Rahilly, professor of clinical biochemistry and medicine at Cambridge University, said: "This new report must be viewed very cautiously as it mostly reports findings in mice, accompanied by human studies so small as to be difficult to interpret."
Brian Ratcliffe, professor of nutrition at Robert Gordon University, Aberdeen, said: "The study raises some concerns about the widespread use of saccharin and should provoke further investigations.
"Sugar sweetened beverages (SSB) make a significant contribution to the intake of free sugars.
"The market leaders' alternatives in the form of 'diet' drinks do not usually contain saccharin so there seems no reason to suggest that swapping to a diet version of your favourite fizzy drink is unwise as a strategy to reduce the intake of free sugars."
Naveed Sattar, professor of metabolic medicine at the University of Glasgow, said: "This is an interesting finding in mice but we have to remember two important things.
"Animal data for many experiments do not show the same effect in humans, which can sometimes be quite the opposite.
"Hence one must be cautious in extrapolating the findings to humans.
"Current epidemiological data in humans do not support a meaningful link between diet drinks and risk for diabetes, whereas sugar rich beverages do appear to be associated with higher diabetes risk.
"So these findings would not make me choose sugary drinks over diet drinks."