研究：食土有益肠胃健康

“食土”在很多国家都被视作异食癖的一种，家长看到孩子食土也会立即制止。不过，最近发表在《生物学季评》杂志上的一篇研究论文指出，食土对人体其实是有益的。研究人员对世界各地有关食土的480多处文献记载进行了分析。他们发现，人类食土并非因为饥荒或者怪癖，而是为保护自身。研究人员分析说，人们食土更多地是为了排除体内毒素、预防疾病和寄生虫。在某些地方，食土者多为刚怀孕的妇女与少儿，因为这两类人对病原体和寄生虫尤其敏感，食土可以为肠胃建起一层保护膜，能够预防病菌，同时还能促进营养物质的吸收。

Parents who have watched in horror as their young children stuff a handful of mud into their mouths while playing in the garden can relax.

For research suggests that eating mud or clay could actually be good for the stomach.

Dining on dirt, or geophagy, is common among many cultures and has been reported in almost every country in the world.

Now more than 480 cultural accounts of the practice — by missionaries, plantation doctors and explorers — have been analysed by researchers at Cornell University in New York.

While no one is suggesting that mud should be the new fad diet, the study, in The Quarterly Review of Biology, found the most plausible explanation for geophagy could be that earth acts as a shield against ingested parasites and plant toxins.

People may also crave dirt because it provides nutrients they lack such as iron, zinc, or calcium, the research found.

Dr Sera Young, who led the study, said the first written account of human geophagy comes from Hippocrates more than 2,000 years ago.

The researchers said: "We hope this paper stimulates more research.

"More importantly, we hope readers agree it is time to stop regarding geophagy as a bizarre, non-adaptive gustatory mistake.

"With these data, it is clear that geophagy is a widespread behaviour in humans that occurs during both vulnerable life stages and when facing ecological conditions that require protection. "

"We found that it was pregnant women and young children who are eating clay, those who are the most vulnerable to infectious diseases," Young said. "It was occurring where the pathogen density was higher, in warm, moist climates."

In studies on rabbits and rats, researchers found that clay in the intestines can act as a barrier, stopping the entrance of viruses and bacteria. It has also been shown that it can help increase nutrient absorption, which is important during early pregnancy and the childhood years for growth.

That isn't actually a new idea: Clay has been used as a stomach soother, including in the antidiarrheal medicine Kaopectate, whose name comes from the clay kaolinite. The drug's manufacturers stopped using the clay in the medicine because of contamination issues with lead.