In a study published in Frontiers in Nutrition, researchers examined the long-term effects of replacing drinking water entirely with sugar-sweetened or sugar-free cola in rats. Over eight weeks, 24 Sprague-Dawley rats were divided into three groups: water, sugary cola, and diet cola. Each group consumed its assigned beverage as the sole fluid source while maintaining a standard diet.
Despite concerns about daily soda intake, the rats showed no significant differences in body weight, body mass index, blood glucose, or lipid profiles after eight weeks. On the surface, they appeared metabolically stable. However, deeper analysis revealed notable physiological changes.
Both cola groups had significantly lower white blood cell counts, indicating leukopenia and possible immune alterations. The sugar-sweetened cola group showed a reduced thymus index and enlarged spleen, suggesting immune organ stress. Meanwhile, the diet cola group exhibited elevated liver enzymes—ALT and AST—pointing to potential liver strain.
Renal markers also differed. The sugar-sweetened cola group had increased blood urea nitrogen levels, indicating kidney burden, though creatinine remained unchanged. Both cola groups demonstrated reduced serum total protein, suggesting broader systemic effects.
Gut microbiota analysis using 16S rRNA sequencing revealed marked dysbiosis in both cola groups. Microbial diversity indices were significantly higher, particularly in the sugar-sweetened group. At the phylum level, Firmicutes declined while Bacteroidota increased, lowering the Firmicutes/Bacteroidota ratio. Beneficial genera such as Lactobacillus were reduced, especially with sugary cola.
Correlation analyses linked certain microbial shifts with immune and renal markers, though causation was not established. The findings suggest that replacing water with cola—whether sugary or diet—may disrupt immune balance, organ function, and gut microbiota, even without obvious metabolic changes.
REFERENCE: Gao H, Li W, Wang X, Ren Y, Li X, & Liu C. (2026). Gut dysbiosis and immune dysfunction induced by chronic cola replacement of water in rats: not just a sugar problem. Frontiers in Nutrition, 12. DOI: 10.3389/fnut.2025.1707842, https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2025.1707842/full
Chronic Cola Consumption Reduces Key Immune Cells, Animal Study Shows
