In vitro examination of the effect of honey in the gastrointestinal tract

Authors: TRAXLER, STE - University Of California, Davis; SPEARMAN, SARAH - University Of California, Davis; Storms, David; Lemay, Danielle; Kable, Mary

Submitted to: Current Developments in Nutrition
Publication Type: Abstract Only
Publication Acceptance Date: 3/14/2022
Publication Date: 8/14/2022
Citation: Traxler, S., Spearman, S., Storms, D.H., Lemay, D.G., Kable, M.E. 2022. In vitro examination of the effect of honey in the gastrointestinal tract. Current Developments in Nutrition. 6/1031. https://doi.org/10.1093/cdn/nzac069.036.
DOI: https://doi.org/10.1093/cdn/nzac069.036

Interpretive Summary: OBJECTIVE: Honey has shown beneficial antibacterial properties in wound healing, but little is known about the effects of honey consumption on human gut health. Herein, we investigate the effects of honey gastric digest on the growth of the common food-borne pathogen Enterotoxigenic E. coli (ETEC) and beneficial lactic acid bacteria within the gastric environment and a small intestine microbial community respectively. METHODS: In Vitro Gastric Digestion: An in vitro digestion of both honey and a simple sugar control (42% fructose, 35% glucose, 23% water) was performed in a simulated gastric electrolyte solution containing pepsin and hydrochloric acid (HCl). Each solution was adjusted to a pH of 2.5, and placed in an incubating shaker at 37', 200rpm for 120 minutes. For ETEC survival experiments, 800,000 CFU/mL of ETEC in BHI was added to each solution before pH adjustment. Samples were collected every 20 minutes, plated on BHI, and colonies counted the following morning. In Vitro Fermentation: Digested honey or control was added at 1% w/v to a small intestine microbial mock community, containing 100,000 cells each of 8 common small intestinal commensal bacteria, and fermented anaerobically for 40 hours at 37' and an initial pH of 5.5. Samples were collected for 16S rRNA analysis; optical density and pH were measured to determine bacterial growth and estimate the relative production of acids in the culture media, respectively. 16S Analysis: V4 region was amplified and sequenced on Illumina MiSeq at UC Davis Tech Core. Sequences were analyzed in Qiime 2. Statistical analyses were performed via DESeq2 in R. RESULTS: Our preliminary data shows that under in vitro gastric digestion conditions, ETEC survival decreases more quickly in honey than a simple sugar control, and this decrease may be partially independent of pH, but total survival is similar at 120 minutes. During in vitro fermentation, differences in the relative abundance of specific taxa between honey and control did not reach statistical significance. CONCLUSIONS: Our pilot experiments suggest honey may affect the survival of gastric pathogens within the stomach. Research is ongoing to confirm these results.

Technical Abstract: OBJECTIVE: Honey has shown beneficial antibacterial properties in wound healing, but little is known about the effects of honey consumption on human gut health. Herein, we investigate the effects of honey gastric digest on the growth of the common food-borne pathogen Enterotoxigenic E. coli (ETEC) and beneficial lactic acid bacteria within the gastric environment and a small intestine microbial community respectively. METHODS: In Vitro Gastric Digestion: An in vitro digestion of both honey and a simple sugar control (42% fructose, 35% glucose, 23% water) was performed in a simulated gastric electrolyte solution containing pepsin and hydrochloric acid (HCl). Each solution was adjusted to a pH of 2.5, and placed in an incubating shaker at 37', 200rpm for 120 minutes. For ETEC survival experiments, 800,000 CFU/mL of ETEC in BHI was added to each solution before pH adjustment. Samples were collected every 20 minutes, plated on BHI, and colonies counted the following morning. In Vitro Fermentation: Digested honey or control was added at 1% w/v to a small intestine microbial mock community, containing 100,000 cells each of 8 common small intestinal commensal bacteria, and fermented anaerobically for 40 hours at 37' and an initial pH of 5.5. Samples were collected for 16S rRNA analysis; optical density and pH were measured to determine bacterial growth and estimate the relative production of acids in the culture media, respectively. 16S Analysis: V4 region was amplified and sequenced on Illumina MiSeq at UC Davis Tech Core. Sequences were analyzed in Qiime 2. Statistical analyses were performed via DESeq2 in R. RESULTS: Our preliminary data shows that under in vitro gastric digestion conditions, ETEC survival decreases more quickly in honey than a simple sugar control, and this decrease may be partially independent of pH, but total survival is similar at 120 minutes. During in vitro fermentation, differences in the relative abundance of specific taxa between honey and control did not reach statistical significance. CONCLUSIONS: Our pilot experiments suggest honey may affect the survival of gastric pathogens within the stomach. Research is ongoing to confirm these results.