过咸食物会给大脑传递不愉快信息

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