Are sweeteners the best option?

Study finds sweeteners can cause problems with how the human body absorbs glucose

Supposedly zero-calorie sweeteners can negatively affect how the human body absorbs glucose, probably because the compounds they are made up of impact the microbes that live in our digestive systems. These are the conclusions of a study led by researchers from the Weizmann Institute of Science, Israel, which indicate that using these substances so widely to replace sugar in food may pose more risks than previously thought.

“The potential clinical implications of this response to the use of NNSs [non-nutritive sweeteners] merit further study,” says Eran Elinav, one of the Weizmann scientists involved in the study.

“It is important to stress that our findings do not imply in any way that sugar consumption, shown to be deleterious to human health in many studies, is superior to non-nutritive sweeteners,” clarifies Elinav. “We believe that sugar consumption should be avoided or minimized, especially in populations that are susceptible to or already suffer from metabolic diseases, such as obesity and diabetes.”

In the paper, published in a recent edition of the scientific journal Cell, the Israeli team and colleagues from Germany and the USA evaluated the effects of four types of NNS widely used by the food industry: saccharin, sucralose, aspartame, and stevia. It is common commercial practice to add about 5g of glucose to sachets of these sweeteners, both to increase product volume and to avoid a potentially unpleasant aftertaste.

“This amount of glucose is considered too small [to have any effect on metabolism]. Even so, we used two control groups to isolate the effects of the NNSs from those that could be linked to the small amount of glucose. One group did not consume any sachets of sweetener, while the other was only given this small amount of glucose,” explains Elinav.

According to the team, one of the driving factors behind the research was the heterogeneous results of studies on the effects of sweeteners on humans in the existing scientific literature. Some studies suggest that using these products has metabolic benefits, some show that they have no detectable effects, while others, depending on the context, show that they can be harmful to human health. The more positive evidence seems to come from testing on animals, whose variables are easier to control. But even these studies have identified considerable differences in the effects of NNSs.

The Weizmann Institute researchers hypothesized that this variability could be influenced by the microbiome of the digestive system, which plays an important role in nutrient absorption and changes considerably from one person to the next, partly due to diet. Previous in vitro and animal studies have suggested that NNSs are capable of affecting these microorganisms and influencing the onset of glucose intolerance, typical of diabetes.

The study

To investigate this possibility in more depth, the team planned a randomized controlled trial of 120 healthy adults. One important detail is that the scientists only recruited volunteers who did not use sweeteners before the study began. Divided into groups according to sweetener type and their respective controls, participants were given a specific number of NNS sachets—less than the maximum considered safe by the industry—to consume each day for two weeks. Before the experiment began, the scientists analyzed the microbiome of all the volunteers to establish a baseline for comparison after the sweeteners had been consumed.

The results revealed that the participants’ oral and fecal microbiomes changed after two weeks of NNS consumption regardless of the type of sweetener added to their diet and the glycemic response of groups that consumed saccharin and sucralose worsened.

“We used the Glucose Tolerance Test (GTT), which is often used to measure the body’s response to sugar consumption,” says Elinav. “The results show that these compounds are probably not inert in the human body. The higher the GTT value, the harder it is for the body to process the sugar, which can increase the risk of diabetes.”

Industry response

Representatives of the sweetener industry have criticized the research. In an official response, the International Sweeteners Association (ISA) argued that the data obtained by the study cannot be relied upon to indicate the potential risks these substances pose to the metabolism.

“In contrast to the hypothesis made by the authors that low-/no-calorie sweeteners can affect human metabolism by alteration of the intestinal microbiome, a recent review of the literature concluded that there is clear evidence that changes in the diet unrelated to low-/no-calorie sweetener consumption are likely the major determinants of change in gut microbiota. Indeed, participants’ diet, while recorded, was not fully controlled in this study. Therefore, the impact of dietary intake aspects cannot be ruled out,” says the statement released by ISA.

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