Comments by "Sasha S" (@sashas3362) on "The Shocking Effects Caffeine Has on Your Brain and Body" video.

I disagree with the claim that coffee doesn't dehydrate. Although you get water when drinking coffee, the coffee causes your cells to excrete electrolytes and this causes an electrolyte imbalance. That is why it can cause a heart attack. Drinking water after your electrolytes get disrupted doesn't always properly rehydrate you because your cells don't actually absorb the water unless you drink water with the proper electrolyte balance to rehydrate and replenish your electrolytes. The water you get from drinking coffee often doesn't get absorbed into your cells to replenish the intracellular fluid but instead remains outside your cells in the form of extracellular fluid (because the electrolyte concentration is greater outside the cells, due to the caffeine causing excretion of the electrolytes, and therefore need to be diluted for the concentration or "osmotic pressure" to become equal to the fluid inside the cell). You can drink all the water in the world but you won't actually become rehydrated until the fluid inside the cells is replenished. It can be very difficult to replenish the intracellular fluid.
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