Sweeteners should 'not be assumed to be safe', scientist warns

Artificial sweeteners should ‘not be assumed to be safe’ because they make cells less able to absorb sugar and change gut microbiome, study says: Experts warn they may raise diabetes risk

  • Weizmann Institute of Science researchers in Israel gave 120 people sweeteners or a placebo for two weeks
  • Those given aspartame and stevia had an altered gut microbiome, they found
  • But those who got saccharin and sucralose were less able to absorb sugar
  • Scientists said the results suggested that sweeteners should not generally be assumed to be safe
  • The World Health Organization is consulting on their safety 

Artificial sweeteners used in diet sodas and low-fat desserts should ‘not be assumed safe,’ an Israeli scientist has warned — after his study found they made it harder for cells to absorb sugar and changed the gut microbiome.

Researchers led by the Weizmann Institute of Science near Tel Aviv, Israel, and Johns Hopkins University in Maryland gave 120 people one of four sweeteners or a placebo up to three times a week for 14 days at doses lower than the recommended limits.

They found those who got aspartame and stevia — often found in diet sodas and juices — had an altered gut microbiome. But those who got saccharin and sucralose — a common sugar substitute in baking — were also less able to absorb sugar.

Dr. Eran Elinav, the microbiologist who led the study, said: ‘We should not assume [sweeteners] are safe until proven otherwise. Until then, caution is advised.’

Previous studies have also linked sweeteners to a higher risk of type 2 diabetes, heart disease and obesity, but have also shown they can help with short-term weight loss.

The above chart shows the time frame of the study (grey line at the top) including the period when participants were receiving either sweeteners or a control (black line pointing down to the six groups). It also shows blood sugar responses (glycemic responses) revealing higher levels in people who got saccharin or sucralose, suggesting they were having trouble absorbing it

The study looked at aspartame, saccharin, stevia and sucralose (stock image)

For the study, published this month in the journal Cell, scientists only recruited healthy people around 29 years old who had not previously consumed a sweetener.

They were randomized into six groups to receive either a sweetener from commercially-available sachets, a sugar or a placebo. 

In the experiment they received supplements up to three times a week, although not in doses higher than the 50 milligrams (mg) per kilo of body weight recommended by the Food and Drug Administration (FDA).

The Food and Drug Administration (FDA) regulates most sweeteners as food additives.

But several — including stevia which can be used in diet drinks — are not closely monitored because they are considered to be ‘generally recognized as safe’ (GRAS).

It has approved all those in the Israeli study as safe for use.

Food additives and GRAS both must be determined by scientists to meet ‘the safety standard of reasonable certainty of no harm under the intended conditions of its use,’ according to the FDA.

They range from being about 100 to more than 700 times sweeter than sugar.

To monitor how sweeteners effected blood sugar levels, participants wore glucose monitors for the whole of the trial. Glucose tolerance tests were also administered.

To further investigate this, stool samples were also taken from participants and implanted into mice who had no gut microbiome.

Results showed problems with absorbing sugar in two of the sweetener groups, while all four showed changes to the gut microbiome.

Elinav, who runs his own lab, told the Times of Israel: ‘Our trial has shown that non-nutritive sweeteners may impair glucose responses by altering our microbiome.

‘In my opinion as a physician, once it has been noted that non-nutritive sweeteners are not inert to the human body, the burden of proof of demonstrating or refuting their potential impacts on human health is at the responsibility of those promoting their use.

‘And we should not assume they are safe until proven otherwise. Until then, caution is advised.’

When asked by DailyMail.com whether his study suggested sweeteners may raise the risk of diabetes, Elinav said: ‘We need to do long-term studies to investigate this.

‘But, given these very substantial findings caution is advised — especially for more at risk groups.’

He added that consuming sugars continued to be a ‘well-proven health risk for obesity, diabetes and their health implications.’

Sweeteners are a popular sugar replacement in the United States, where more than a third of adults are obese, and many are looking to lose weight.

But while evidence suggests they may help with short-term weight loss, the long term impacts are less clear — with some papers warning they may even lead to weight gain.

The World Health Organization launched a public consultation on the health effects of sweeteners this year, as they make their way into more and more foods.

In its meta-analysis of studies, the organization concluded: ‘Results from prospective cohort studies suggest the possibility of long-term harm in the form of increased risk of obesity, type 2 diabetes, cardiovascular diseases and mortality.

‘Further research is needed to determine whether the observed associations are genuine, or a result of [study design].’

In the United States, most sweeteners are regulated by the FDA as food additives. But stevia — one of the four sweeteners in the study — does not fall into this category because it is ‘generally recognized as safe’ (GRAS). 

Food additives must undergo premarket review and approval by the FDA before they can be used in food, while GRAS substances do not require premarket approval. This allows a company to independently decide whether or not to use them without notifying the FDA. 

All four sweeteners tested in the study have been approved for consumption by the regulatory body. 

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