But not in short supply. I have never heard of a single American having a sodium deficiency, but millions upon millions consume 10 or 20 times the salt they need daily. It may be vital but it is a lot like breathing air. It takes a concerted effort not to consume ample amounts.
Ever seen someone who's been overcome by heat sickness? Common symptoms are: extreme fatigue, muscle cramps, cold chills, vertigo or dizziness, nausea, headache, and fainting.
All of those symptoms are caused by a lack of sufficient sodium in the body, while under heat stress. I know them well, having worked outdoors as a tradesman for the last forty years.
I suffered the ill effects of heat sickness for about ten years, until I happened to visit with a nutritionist, who educated me on the root cause of those difficulties.
Essentially, the body loses minerals through the pores when we sweat; but it's the loss of the mineral, sodium, that brings on the symptoms of heat sickness. Simply replacing that lost sodium with sea salt tablets cures heat sickness within minutes.
Since discovering this simple cure, I've always kept a large bottle of sea salt tablets on my truck, and have made sure that my employees take them daily, during the hot months. About 500 milligrams per 25 pounds of body weight (per day) is best.
It goes without saying, that you should consume lots of water, too.
Being acutely aware of this phenomebon, I've noticed over the decades that most people exhibit one or more symptoms of heat sickness, even when under mild conditions of heat and physical exertion. I can't help but conclude, from that simple observation, that most Americans are chronically deficient in sodium.