When I was in high school, I lived in Southern California on the edge of the Colorado Desert. It was hot. In the summer it was especially hot. One summer I worked in a dairy washing bottles. That was incredibly hot.

One day I passed out. Our family doctor quickly diagnosed my problem. Too little salt. Our bodies need some salt, and I had sweated mine away.

Until last year, just like most people, I went to the other extreme. Too much salt.

Because once in my life I got too little salt, I...