英语听力文摘 English Digest 719 每日一个洋葱可以和医生说再见么？（在线收听）

Does An Onion A Day Keep The Doctor Away?

Have you ever wondered why your eyes water when you chop onions?

Like Tear Gas

Despite what you might think, the smell of onions is not what makes most people cry. You see, an onion gets it distinctive taste from compounds that contain sulfur atoms. When you slice an onion, you damage its cells, triggering a chemical reaction that converts these compounds into an acid that acts like tear gas.

At the same time, the byproducts of this reaction condense to form the molecules responsible for the onion’s pungent odor. In other words, the same chemical reaction that makes you weepy also releases the onion’s smell.

Garlic And Health Benefits

A similar thing happens when you chop garlic. When it’s still in bulb form, garlic doesn’t smell like much. It’s only when you mince or dice the garlic’s cells that a chemical reaction releases the smell we associate with garlic.

However, no one cries from slicing garlic. This is because the byproducts of the chemical reaction that takes place in garlic are different from the byproducts you get when you chop an onion.

Scientists suggest that the same chemical that gives garlic and onions their distinctive smell helps them fight off bacteria and fungus and parasites. There might be something after all behind all those reports that garlic and onions are good for you.

每日一个洋葱可以和医生说再见么？

你有没有想过为什么切洋葱时眼睛会流泪？

像催泪瓦斯

不管你怎么想，洋葱的味道并不是让大多数人哭泣的原因。你看，洋葱从含有硫原子的化合物中获得独特的味道。当你切洋葱时，你会破坏洋葱的细胞，引发一种化学反应，将这些化合物转化为一种酸，这种酸起到催泪瓦斯的作用。

同时，这一反应的副产物凝结形成了洋葱刺鼻气味的分子。换句话说，让你流泪的化学反应也会释放洋葱的气味。

大蒜和健康益处

当你切碎大蒜时，也会发生类似的事情。当它还是球状时，大蒜闻起来不太香。只有当你将大蒜的细胞切碎或切丁时，化学反应才会释放出我们与大蒜相关的气味。

然而，没有人因为切大蒜而哭泣。这是因为大蒜中发生的化学反应的副产物与你切洋葱时得到的副产物不同。

科学家们认为，赋予大蒜和洋葱独特气味的化学物质有助于它们抵御细菌、真菌和寄生虫。在所有这些报道背后，大蒜和洋葱对你有好处。