The Evolutionary Link Between Diet and Stomach Acidity

For Immediate Release

DeAnna Beasley debeasl2@ncsu.edu 919.513.8073

Tracey Peake tracey_peake@ncsu.edu

An analysis of data on stomach acidity and diet in birds and mammals suggests that high levels of stomach acidity developed not to help animals break down food, but to defend animals against food poisoning. The work raises interesting questions about the evolution of stomach acidity in humans, and how modern life may be affecting both our stomach acidity and the microbial communities that live in our guts.

“我们开始了这个项目，因为我们希望更好地了解胃酸度，饮食和生活在鸟类和哺乳动物的肠道的微生物之间的关系，”北卡罗来纳州立大学博士队研究员Deanna Beasley说：一篇论文的通讯作者关于工作。“我们的想法是，这可以为观察人类胃在影响肠道微生物的角色以及对人类健康意味着什么意思提供一些背景。”

研究团队——包括科学家ington University and the University of Colorado, Boulder – examined all of the existing literature on stomach acidity in birds and mammals, and found data on 68 species. They then collected data on the natural feeding habits of each species. The researchers then ran an analysis to see how feeding behavior was related to stomach acidity.

The researchers found that scavengers, or species that eat food at high risk of microbial contamination, have more acidic stomachs. 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 says. “The next step will be for scientists to examine the microbial ecosystems in the guts of these animals to see how these ecosystems have evolved. Do animals with high stomach acidity have smaller or less diverse populations of gut microbes? Or do they simply host microbes that can survive in acidic environments?”

One surprise was that, while the researchers classified humans as omnivores, human stomachs have the high acidity levels normally associated with scavengers. Meanwhile, the literature shows that medical treatments – from surgery to antacids – can significantly alter the acidity in a human stomach.

“这提出了关于人类如何发展的重要问题，我们的物种与食物随着时间的推移，饮食和药物的现代变化如何影响我们的胃，我们的肠道微生物和最终 - 我们的健康，”Beasley说。“研究界已经探索的那些是问题，答案应该是有趣的。”

The paper, “The Evolution of Stomach Acidity and Its Relevance to the Human Microbiome,” will be published July 29 in the journalPLOS ONE. The paper was co-authored by Rob Dunn of NC State, Amanda Koltz of Washington University, and Joanna Lambert and Noah Fierer of UC Boulder.

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Note to Editors:The study abstract follows.

“The Evolution of Stomach Acidity and Its Relevance to the Human Microbiome”

Authors: DeAnna E. Beasley and Rob R. Dunn, North Carolina State University; Amanda M. Koltz, Washington University; Joanna E. Lambert and Noah Fierer, University of Colorado, Boulder

Published: July 29,PLOS ONE

DOI: 10.1371/journal.pone.0134116

Abstract:胃酸可能是塑造脊椎动物肠道中发现的微生物社区的多样性和组成的关键因素。我们进行了系统审查以测试脊椎动物胃的关键作用是通过在进入肠道之前通过滤除新的微生物分类群来维持肠道微生物群落的关键作用。我们提出了腐蚀或近摄系统发育亲属的生物体上的物种应该需要最严格的过滤器（测量为高胃酸），以保护来自外部微生物的保护。相反，喂养较低的营养水平或与它们的食物上的物种（例如，草本病变）应该需要最少限制的过滤器，因为病原体暴露的风险较低。与哺乳动物和鸟类分类群中的营养群体胃酸度的比较表明，与在昆虫或鱼类的系统嗜血或鱼类上喂养的食草动物或食肉动物相比，清除剂和肉食病毒具有显着高的胃酸。此外，我们发现胃酸在物种内不同（随着年龄的增长）或在肥胖症手术等治疗中，对肠细菌病原体和社区的影响符合我们的假设，即胃作为生态过滤器。这些结果共同突出了在研究内部和跨越物种内部和跨越物种时测量胃pH的重要性。