That being said, there is a tendency to ascribe a special significance to pregnancy cravings. “Women see pregnancy as a time to indulge,” says Julia Hormes, assistant professor of psychology at the University of Albany in the US. “There are a lot of myths around ‘eating for two’ and giving the foetus what it needs, but really there’s not a lot of support for those ideas.”

换句话说，怀孕期间的食土癖可以被视为在孕期产生的一种特殊渴望。“女人都会将孕期看作是一段可以纵容自己享受的时光”，美国阿伯尼大学（University of Albany）心理学副教授茱莉亚•霍尔莫斯（Julia Hormes）说道，“关于‘大的不吃，小的也得吃’以及‘给腹中的胎儿一切它需要的’产生了许多传说，也成为孕妇食无节制的借口，但实际上这样的理论并没有太多的科学支撑。”

Hormes says in reality these cravings have a whole lot to do with culture, and not a lot to do with biology.

霍尔莫斯解释，女人在怀孕期间产生的各种渴望其实更多地与文化联系在一起，与生物学并没有太大关系。

If there are culture-specific beliefs around eating dirt, then women in Cameroon are as likely to crave it as women in Europe or North America might feel cravings for chocolate or ice cream. Just because someone craves something doesn’t mean it’s good for them.

假如说食土习俗和文化信仰有关，那么喀麦隆的女人吃土这个行为其实和欧美的女人爱吃巧克力别无二致。每个人都有自己特别爱吃的东西，爱吃的原因并不一定是因为这种食物能给他们带来什么好处，而仅仅是因为他们爱吃而已。

Still, the inclination towards geophagy clearly arises from somewhere, seeing as it’s found even in cultures for which it has no such significance. Studies of animals suggest an adaptive, biological explanation could be at least part of the story.

我们同时看到，在那些所谓“没有食土习俗”的国家里，也出现了越来越多的吃土现象。通过动物实验，我们相信适应性和生物学的解释至少能说明一部分人类吃土的原因。

When elephants, primates, cattle, parrots and bats engage in geophagy, for example, it is generally considered to be serving a useful purpose. Despite this, some of the same scientists who consider geophagy normal in animals still see it as abnormal in humans.

当大象、灵长类动物、牛、鹦鹉和蝙蝠都存在食土行为，那么我们总体上可以认为“吃土”是有实际意义的。可尽管一些科学家同意动物吃土是正常行为，他们仍旧认为人类吃土是反常行为。

Undoubtedly some cases of dirt eating do indeed involve psychiatric problems, but drawing a line is difficult. In 2000, the US Agency for Toxic Substances and Disease Registryconcluded that pathological levels of soil consumption constituted more than 500 mg per day, but even they conceded that this was an arbitrary measurement.

毋庸置疑的是，一些吃土的案例的确存在着精神疾病的问题，但如何认定吃土者是否患有精神疾病则是一个难题。美国有毒物质与疾病登记署（US Agency for Toxic Substances and Disease Registry）于2000年规定，每天500毫克的黏土食用量为判定病态和非病态的标准——每天服食超过500毫克的黏土则为病态——然而有关部门任性地表示，这个标准只是他们随便定的。

“Because geophagy has been so extensively documented as a culturally-based phenomenon, I'm not inclined to view it as ‘abnormal’ behaviour,” says Ranit Mishori, a professor of family medicine and doctor at Georgetown University Medical Center. “If, however, this behaviour is associated with any clinical abnormalities, I would have a conversation about how to avoid it.”

“许许多多的文献都表明，食土习俗是一个文化现象，因此我不赞同将其看作一种‘不正常’的行为”，乔治城大学医学中心（Georgetown University Medical Center）的家庭医学教授瑞丽特•米歇里（RanitMishori）表示，“假如说这种行为与临床中所说的异常有任何关联，那我会告诉你该如何避免。”

Clearly there are downsides to consuming dirt. The presence ofsoil-borne diseases and toxic substances in the clay is a major issue, as is the possibility that the very deficiencies supposedly cured by the practice might even be caused by them.

当然吃土的危害也是非常明显的。土传性病害和泥巴里的有毒物质就是一个非常大的问题，而同样不容忽视的是，吃土本身也会导致人体微量营养素的缺乏。

Eating dirt can even become an addiction, an impulsive act hidden from others. “With geophagy, the language of substance abuse is really common,” says Young.

吃土除了会上瘾，吃土这一行为也有可能成为一种被极力掩饰的冲动行为。而塞拉•杨表示：“与食土癖相比，药物滥用是一种更常见的现象”。

It’s easy to dismiss geophagy as a disgusting habit of children, a wacky pregnancy craving, or an exotic behaviour from far-away lands, but none of these approaches really do it justice. Moreover, such characterisations risk alienating people who find it difficult to explain their ‘unnatural’ desires.

人们很容易将食土癖简单地理解为孩子们一种恶心的习惯、孕妇们在孕期古怪的渴望，或是来自地球另一端的异国文化，但这些看法并不能真的给食土癖正名。另外，这种分类和定义的方法过于草率，会令食土的族群更难向我们解释他们那“反常”的爱好。

To fully grasp this phenomenon, and understand whether its effects are positive, negative or a subtle mix of the two,researchers need to undertake hypothesis-driven tests that take both biomedical and cultural factors into account.

为了完全认识食土这一现象，并充分了解食土带来的影响是正面、负面，或是两者皆有，研究者们需要进行各种假说驱动的实验，将医学生物学和文化的因素都考虑在内。

“I’m not saying ‘everyone should be eating three spoonfuls of earth a day’”, says Young. “But we certainly don’t know enough yet to write this behaviour off entirely.”

“我不是在建议大家每天都吃三大勺的土”，塞拉•杨说，“但我们现在还没有充分的科学研究来完整地解释食土行为。”