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Too Much Salt Gets Bitter and Sour Involved
听力内容：
60秒科学节目（SSS）是科学美国人网站的一套广播栏目，英文名称：Scientific American – 60 Second Science,节目内容以科学报道为主，节目仅一分钟的时间，主要对当今的科学技术新发展作以简明、通俗的介绍，对于科学的发展如何影响人们的生活环境、健康状况及科学技术，提供了大量简明易懂的阐释。
Too little salt makes for a bland meal. But too much is offensively briny. Now, scientists have discovered why too much tastes bad. The work is in journal Nature. [Yuki Oka et al., High salt recruits aversive taste pathways]
As the previous podcast noted, the cells that process taste send a unique signal to the brain for each kind of flavor. The signals for sweet and umami make animals crave more, while sour and bitter are often rejected. But saltiness is appealing in low doses and aversive at high levels. The researchers found out why: too much salt activates the cells that sense sourness and bitterness, sending unpleasant signals to the brain and transforming a tasty bite into a turn-off.
The study used mice unable to taste sourness, bitterness, or both. Animals that could still sense one of the flavors rejected overly salty water. But mice unable to taste sour and bitter were happy to lick up liquid that was far too briny for normal animals.
With salt being a variable flavor, our bodies can better keep its levels within a healthful range. And leave a good taste in the mouth.
—Sophie Bushwick
