Having recently developed our 'Crazy Sweat Facts' page for kids, it became clear how amazing the human sweat gland really is. While digging for zany facts kids would enjoy reading, we came across some pretty outstanding figures related to these little sweat factories. Consider the following, and I think you will agree.
To start with, sweat glands are tiny. Side by side, you could fit, on average, about 30 sweat glands across the face of a dime. Most sweat glands are concentrated on the soles of our feet - using the dime again, about 1600 glands squeeze into an area the size of that coin. A single sweat gland produces 10 nanoliters of sweat per minute. For the less scientifically inclined, a nanoliter is one billionth of a liter. To put that in perspective, it would take a sweat gland about 35 days to fill one teaspoon. Having said that, systemically, humans can produce up to 3.7 liters of sweat per hour. That's one teaspoon every 5 seconds! Given that sweat contains 0.5% salt, my pharmacist background immediately converts that ratio into a logical value, that is, mass or weight. In other words, 3.7 L of perspiration would yield 18.5g of salt. That's roughly 4 teaspoons of salt per hour. It's no wonder Gatorade sales are in excess of 3 billions dollars annually and the brand is estimated to be worth about 5 billion dollars*.