This in vitro study assessed the effects of three artificial sweeteners — aspartame, saccharin, and sucralose — on the interactions between the gut microbiota and the intestinal epithelium. To model the gut microbiota, two species of bacteria were isolated: E. coli and E. faecalis. To model human epithelial cells, Caco-2 cells (an immortalized cell line of human colon adenocarcinoma cells) were used.
The investigators exposed both bacteria to varying concentrations of each sweetener (up to 1,000 μmol) for four days and assessed the effects on bacterial growth.
They exposed both bacteria to 100 μmol of water and 100 μmol of each sweetener in the presence or absence of zinc sulfate (a sweet-taste inhibitor) for 24–48 hours. The purpose of these 16 expositions was to assess the biofilm formation and hemolysin production of each bacterium.
They added Caco-2 cells to each bacterium and exposed this combination to water and each sweetener in the presence or absence of zinc sulfate. The purpose of these 16 expositions was to assess the adhesion of the bacteria to the Caco-2 cells, the invasion index of the bacteria (by measuring the intracellular concentrations of the bacteria in the Caco-2 cells), and the cytotoxicity of each bacterium-sweetener combination (by measuring the number of live Caco-2 cells after exposure).
Exposure to 1,000 μmol of saccharin reduced the growth of E.coli. The other two sweeteners didn’t affect the growth of either bacterium.
Compared to water, all three sweeteners increased the biofilm formation of E.coli. Only aspartame increased the biofilm formation of E. faecalis. The sweeteners didn’t affect the hemolysin production of either bacterium.
All three sweeteners increased the adhesion of E. coli and E. faecalis to Caco-2 cells and the adhesion index of E. faecalis. Sucralose and aspartame also increased the invasion index of E. coli. Caco-2 cell viability was reduced by E. faecalis exposed to sucralose or aspartame and by E. coli exposed to saccharin or sucralose.
Zinc sulfate reduced the increase in bacterial biofilm formation and the adhesive, invasive, and cytotoxic effects observed after sweetener exposure.
While these results suggest that artificial sweeteners could negatively affect our gut microbiota, our gut microbiota is far more complex than the model used in this study, and its health can be promoted by many factors, such as stress management, regular exercise, and a high-fiber diet.
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