Sweeteners can imbalance blood and gut chemistry, according to new research that suggests diet sodas and other sugar-free sweet treats may affect the body in unanticipated ways.

So-called non-nutritive sweeteners like saccharin and sucralose have long been used as alternatives to sugar in order to combat weight gain, obesity, and metabolic diseases such as diabetes.

The sugar replacements were once thought to be relatively inert, however mounting evidence indicates otherwise.

The study from the Weizmann Institute of Science in Israel found certain sweeteners can impact the way our bodies regulate glucose levels in the blood.

"Our trial has shown that nonnutritive sweeteners may impair glucose responses by altering our microbiome, and they do so in a highly personalized manner, that is, by affecting each person in a unique way," said Eran Elinav, an immunologist at the Weizmann Institute and co-author of the research. "In fact, this variability was to be expected, because of the unique composition of each person's microbiome."

Made up of trillions of bacteria and other microorganisms in the digestive tract, the gut microbiome plays an important role in digestion and supporting the immune system. Changes to the composition and function of the microbiome can lead to health problems and metabolic disorders.

In a trial involving 120 participants, the researchers found all four sweeteners studied－saccharin, sucralose, stevia, and aspartame－altered the gut biome. In the case of saccharin and sucralose, the alterations led to impaired glucose tolerance, or a decreased ability to metabolize glucose in the blood. The four substances studied are all widely used, however there are more than a dozen other commercially available sweeteners that were not included in the research.

The results suggest people should consider limiting their intake of sweeteners, since glucose intolerance is associated with a number of metabolic disorders, including diabetes.

The researchers stressed that returning to a high-sugar diet is not preferable, since sugar itself is linked to a host of health problems, including weight gain, certain cancers, heart disease, and diabetes.

"Our findings do not imply in any way that sugar consumption, shown to be deleterious to human health in many studies, is superior to nonnutritive sweeteners," said Elinav.

Francisco Guarner, who is director of the Digestive System Research Unit at the Vall d'Hebron University Hospital in Barcelona and who was not involved in the research, said it is difficult to draw firm conclusions from the study. In particular, Guarner took issue with the high quantities of sweeteners given to the trial participants, which he said far exceeded normal levels.

"Personally, I am of the opinion that there is only one acceptable conclusion, which is also important: the fact that a substance is not absorbable and therefore does not enter the blood does not mean that it is inert," he said. "The substance influences the microbiota of the large intestine and can induce negative or positive changes."