Stomach acid defends against food poisoning

High levels of stomach acid not only help animals break down food, but it also defends them against food poisoning, a study has revealed.

"We started this project because we wanted to better understand the relationship between stomach acidity, diet and the microbes that live in the guts of birds and mammals," said corresponding author DeAnna Beasley, a post-doctoral researcher at North Carolina State University.

"Our idea was that this could offer some context for looking at the role of the human stomach in influencing gut microbes, and what that may mean for human health," Beasley noted in the Public Library Of Science (PLOS) One journal.

To see how feeding behaviour was related to stomach acidity, the team examined all of the existing literature on stomach acidity in birds and mammals.

They found that scavengers, or species that eat food at high risk of microbial contamination, have more acids.

This acidity allows the stomach to act as a filter, effectively controlling which microbes can pass through the stomach to the gut.

"The finding confirms our hypothesis, but you have to get that confirmation before moving forward," Beasley explained.

While humans are classified as omnivores, human stomachs have the high acidity levels normally associated with scavengers and medical treatments can significantly alter the acidity in a human stomach.

"This raises significant questions about how humans have evolved, our species' relationship with food over time, and how modern changes in diet and medicine are affecting our stomachs, our gut microbes and - ultimately - our health," Beasley concluded.