Geophagy, the consumption of clay or similar substances, is known as an evolved behavior that protects vulnerable populations, such as pregnant women and children, against gastrointestinal injury. However, perplexing questions remain, like the presence of geophagy in the absence of overt gastrointestinal infection and the potential causal relationship between geophagy and iron deficiency anemia. In this review, we hypothesize that geophagy is an inflammation-mediated sickness behavior regulated via the vagus nerve. We further hypothesize that the gut microbiome plays a critical role in mediating the relationship between inflammation and geophagy. By including inflammation and the microbiome within the existing protection hypothesis, we can explain how subclinical gastrointestinal states induce geophagy. Furthermore, we can explain how gastrointestinal inflammation is responsible for both geophagy and iron-deficiency anemia, explaining why the two phenomena frequently co-occur. Ultimately, defining geophagy as a sickness behavior allows us to integrate the gut-brain axis into geophagy research.

中文翻译：

---

重新审视食地行为：微生物介导的胃肠道炎症的进化疾病行为

食土，即消耗粘土或类似物质，被认为是一种进化行为，可以保护孕妇和儿童等弱势群体免受胃肠道损伤。然而，令人困惑的问题仍然存在，例如在没有明显胃肠道感染的情况下是否存在食土现象，以及食土现象与缺铁性贫血之间的潜在因果关系。在这篇综述中，我们假设食土是一种通过迷走神经调节的炎症介导的疾病行为。我们进一步假设肠道微生物组在调节炎症和食土之间的关系中发挥着关键作用。通过将炎症和微生物组纳入现有的保护假设中，我们可以解释亚临床胃肠道状态如何诱导食土。此外，我们可以解释胃肠道炎症如何导致食土和缺铁性贫血，从而解释为什么这两种现象经常同时发生。最终，将食土定义为一种疾病行为，使我们能够将肠-脑轴整合到食土研究中。