研究：食土有益腸胃健康

“食土”在很多國家都被視作異食癖的一種，家長看到孩子食土也會立即制止。不過，最近發表在《生物學季評》雜誌上的一篇研究論文指出，食土對人體其實是有益的。研究人員對世界各地有關食土的480多處文獻記載進行了分析。他們發現，人類食土並非因爲饑荒或者怪癖，而是爲保護自身。研究人員分析說，人們食土更多地是爲了排除體內毒素、預防疾病和寄生蟲。在某些地方，食土者多爲剛懷孕的婦女與少兒，因爲這兩類人對病原體和寄生蟲尤其敏感，食土可以爲腸胃建起一層保護膜，能夠預防病菌，同時還能促進營養物質的吸收。

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.