Metabolism and metabolic effects of the alternative sweeteners erythritol and xylitol

Obesity has reached dramatic proportions worldwide. It represents a significant health and economic burden as it is linked to an increased risk of non-communicable diseases (NCDs), such as cardiovascular diseases, cancer, type 2 diabetes mellitus (T2DM), and chronic respiratory diseases. Obesity is a complex condition caused by a combination of different factors. An unhealthy diet - especially high sugar consumption - is an important determinant of obesity. Therefore, the World Health Organization (WHO) recommends reducing the consumption of added sugars to less than 10% of total energy intake as an effective and low-cost measure to prevent as well as to treat obesity.
Consequently, low-caloric sweeteners (LCS) have garnered widespread interest as sugar substitutes to reduce added sugar intake without cutting on the sweet taste. There are many different LCS. Although they can be grouped by common properties (sweet taste, caloric content), each molecule is metabolized differently and has its own characteristics. Therefore, extrapolating the effects of one sweetener to other sweeteners, even within the same group, is not appropriate. Studies on each parameter of interest for each sweetener are warranted before drawing general conclusions.
This thesis focused on assessing the potential of the low-caloric bulk sweeteners erythritol and xylitol as sugar and artificial low-caloric sweeteners substitutes. Among all aspects necessary to describe their full potential as substitutes, this work aimed to deepen the topics of absorption and metabolism, and to assess specific metabolic effects. These aims were pursued in three clinical trials.
In the first trial, we determined the absorption of different concentrations of erythritol and xylitol and their potential metabolization into erythronate. For this purpose, we conducted a study in 17 healthy volunteers who received intragastric solutions of different concentrations of erythritol or xylitol. We assessed plasma concentrations of erythritol, xylitol, and erythronate at fixed time intervals after administration. We found a dose-dependent and saturable absorption of erythritol, and very low absorption of xylitol. We demonstrated a dose-dependent metabolization of erythritol into erythronate, and no metabolization of xylitol into erythronate.
In the second trial, we investigated whether a chronic intake of erythritol and xylitol impacts glucose absorption in humans with obesity, based on previous findings observed in rat models. Participants with obesity were randomized to consume either 36 g erythritol, 24 g xylitol, or no substance (control group) daily for five to seven weeks. Before and after the intervention we assessed intestinal glucose absorption during an oral glucose tolerance test by means of 3-Ortho-methyl-glucose concentrations in plasma. We found that a chronic intake of the natural sweeteners erythritol and xylitol does not affect intestinal glucose absorption in humans with obesity.
In the third trial, we assessed the impact of a chronic intake of erythritol and xylitol on vascular function, abdominal fat and blood lipids, glucose tolerance, uric acid, hepatic enzymes, creatinine, gastrointestinal tolerance, and dietary patterns in humans with obesity. Participants were randomized to consume either 36 g erythritol, 24 g xylitol, or no substance (control group) daily for five weeks. The parameters mentioned above were assessed before and after the intervention. We found that the chronic intake of erythritol and xylitol did not affect vascular function and had no impact on abdominal fat, glucose tolerance, uric acid, hepatic enzymes, and creatinine. Gastrointestinal tolerance was good, except for a few diarrhea-related symptoms. Participants of all groups reduced their consumption of sweetened beverages and sweets compared to pre-intervention. These results suggest that erythritol and xylitol have no negative effects regarding the parameters assessed, even when consumed by participants with obesity, who are particularly at risk of cardiovascular diseases, hepatic steatosis, and type 2 diabetes mellitus.
In summary, these findings support the view that erythritol and xylitol are sweeteners that do not induce the negative effects observed in association with a high sugar consumption. Therefore, both sweeteners can be helpful in reducing sugar consumption and thus contribute to combating overweight, obesity, T2DM, and other associated NCDs.