Effects of Energy Drink Acute Assumption in Gastrointestinal Tract of Rats

Abstract

Energy drinks (EDs) are non-alcoholic beverages containing high amounts of caffeine and other psychoactive substances. EDs also contain herbal extract whose concentration is usually unknown. EDs can have several adverse effects on different organs and systems, but their effects on the gastrointestinal (GI) tract have been poorly investigated. To determine the acute effects of EDs on the GI tract, we administered EDs, coffee, soda cola, or water to Sprague-Dawley rats (n = 7 per group, randomly assigned) for up to five days, and analyzed the histopathological changes in the GI tract. Data were compared among groups by Kruskal-Wallis or Mann-Whitney tests. We found that, while EDs did not cause any evident acute lesion to the GI tract, they triggered eosinophilic infiltration in the intestinal mucosa; treatment with caffeine alone at the same doses found in EDs leads to the same effects, suggesting that it is caffeine and not other substances present in the EDs that causes this infiltration. The interruption of caffeine administration leads to the complete resolution of eosinophilic infiltration. As no systemic changes in pro-inflammatory or immunomodulating molecules were observed, our data suggest that caffeine present in ED can cause a local, transient inflammatory status that recruits eosinophils.

Keywords: caffeine; energy drinks; eosinophils.

Figure 1

Energy drinks (ED) and coffee trigger eosinophilic infiltration in the mucosa of stomach and intestine in rats. (A). Representative histological staining of stomach sections from after 5 days with the indicated treatment. Upper panels: hematoxylin/eosin (H&E) staining; lower panels: Pagoda red staining. (B). Histogram showing the number of eosinophils per high-powered field (HPF) after five days of the indicated treatment. Data are mean ± SD of ten different counts. (C). Representative histological staining of small intestine sections from after 5 days with the indicated treatment. Upper panels: H&E staining; lower panels: Pagoda red staining. (D). Histogram showing the count of eosinophils per HPF after five days of the indicated treatment. Data are median ± interquartile range of ten different counts. * p < 0.05; *** p < 0.001.

Figure 2

Caffeine does not induce systemic inflammation, despite eosinophilic reaction in the GI tract. Plasma levels of the indicated immunomodulatory molecules, as measured in rats after 5 days of caffeine administration. Concentrations are expressed as pg/mL, with the exception of mtDNA, which is expressed as number of copies per mL. Data are median ± interquartile range of seven samples, each in duplicate. ED = Energy Drink.

Figure 3

Caffeine triggers eosinophilic infiltration in the mucosa of intestine in rats. Rats assumed a beverage containing caffeine for five days, followed by ten days without assumption. (A). Representative Pagoda red staining of intestine sections before caffeine assumption (0), after 5 days of treatment (5), after five more days without caffeine assumption (10) and after ten days without caffeine assumption (15). (B). Histogram showing the number of eosinophils per HPF at the same time points. Data are median ± interquartile range of five independent counts on five animals. * = p < 0.05.