Abstract:
The consumption of sugar-free foods is growing because of their low-calorie content and the health concerns about products with high sugar content. Sweeteners that are frequently several hundred thousand times sweeter than sucrose are being consumed as sugar substitutes. Although nonnutritive sweeteners (NNSs) are considered safe and well tolerated, their effects on glucose intolerance, the activation of sweet taste receptors, and alterations to the composition of the intestinal microbiota are controversial. This review critically discusses the evidence supporting the effects of NNSs, both synthetic sweeteners (acesulfame K, aspartame, cyclamate, saccharin, neotame, advantame, and sucralose) and natural sweeteners (NSs; thaumatin, steviol glucosides, monellin, neohesperidin dihydrochalcone, and glycyrrhizin) and nutritive sweeteners (polyols or sugar alcohols) on the composition of microbiota in the human gut. So far, only saccharin and sucralose (NNSs) and stevia (NS) change the composition of the gut microbiota. By definition, a prebiotic is a nondigestible food ingredient, but some polyols can be absorbed, at least partially, in the small intestine by passive diffusion: however, a number of them, such as isomaltose, maltitol, lactitol, and xylitol, can reach the large bowel and increase the numbers of bifidobacteria in humans. Further research on the effects of sweeteners on the composition of the human gut microbiome is necessary.
Summary:
The current paper by Ruiz-Ojeda et al. reviews the published literature regarding the effects of different low/no calorie sweeteners on the composition of microbiota in the human gut.
The authors note that low/no calorie sweeteners have been critically evaluated by the US Food and Drug Administration (FDA), the European Food Safety Authority (EFSA), and Codex Alimentarius and are safe. However, they suggest that their effects on gut microbiota have not been completely elucidated and that human clinical trials are sparse. The paper claims that, among NNSs [non-nutritive sweeteners], saccharin and sucralose would shift the populations of gut microbiota. It further suggests that the ingestion of saccharin by animals and humans showed alterations in metabolic pathways linked to glucose tolerance and dysbiosis in humans. However, as also pointed out by the authors, the clinical relevance of these findings in humans is not clear.
Given the limitations of the studies published up to date, the authors state that there is a need to perform well-designed, long-term, double-blind, placebo-controlled, randomized clinical trials with appropriated doses and adequate subject sizes to evaluate any potential impact of sweeteners on intestinal microbiota and how they could affect major outcomes and risk biomarkers related to chronic diseases.
On the other hand, another recently published review of the literature by Lobach et al (2019) concluded that current studies establish no evidence of any adverse effect of low/no calorie sweeteners on the gut microbiota at doses relevant to human use and that results of metabolism and safety studies show no evidence of a likely mechanism for a clinically relevant effect on gut microbiota. Dietary changes unrelated to low/no calorie sweeteners’ consumption are likely the major determinants of change in gut microbiota composition, confirming the viewpoint supported by all the major international food safety and health regulatory authorities that low/no calorie sweeteners are safe at currently approved levels.
