There’s a ___1___ that’s had scientists puzzled: the practice of geophagy—eating dirt. People around the world ___2___, and not just when they’re hungry enough to eat anything. So is there any nutritional or health benefit? A meta-analysis published in the Quarterly Review of Biology may offer a clue. [Sera Young et al., "Why on Earth?: Evaluating Hypotheses about the Physiological Functions of Human Geophagy," in press]

Researchers collected more than 480 reports from missionaries, plantation doctors, explorers and anthropologists. These included who was eating dirt and ___3___. Seems that dirt doesn’t offer much in the way of nutrition—but it may protect against toxins, pathogens and parasites.

Dirt is most commonly eaten by women in early stages of pregnancy and preadolescent children. Both are particularly at risk from pathogens and parasites. Also, people tend to eat dirt when they’re suffering from gastrointestinal distress. The distress probably doesn’t come from the dirt, which is usually clay found deep in the ground and that doesn’t ___4___ pathogens. Plus people often boil the clay before eating.

Scientists say more research is needed to confirm the hypothesis that dirt has health benefits. But they hope this offers evidence that eating dirt isn't, well, as ___5___ as it may seem.
【视听版科学小组荣誉出品】
habit munch on dirt under what circumstances house bizarre
科学家们对某个习俗相当不解：食土癖。世界各地都有食土者，不仅仅是因为他们饿到一定境界才这样……食土营养吗？健康吗？看一看《生物学季评》上的分析荟萃也许就会找到点线索。 研究人员从传教士、农林医生、探险家、人类学家那里收集了480多份报告，其中包括何人因何原因而食土。从报告来看，泥土并没有多少营养价值，不过倒是有可能帮助人体抵抗毒素、病原体以及寄生虫的侵害。 在青少年以及处于怀孕初期阶段的妇女中食土现象最为普遍，因为这两者都极易受到寄生虫以及病原体的侵害。肠胃病人犯病时也会食土，但倒不是因为食土才受病痛折磨，因为他们食用的土都是深埋在地下的黏土，这些黏土中不存在病原体，更何况他们在食用之前还会煮一煮。 科学家们认为要证实食土对健康有益这个假设还需要更深入地研究，不过他们希望通过这项研究可以让人们了解：食土其实并不是什么怪癖。（俺还是接受不了啊。。。