That's true, of course, but he did go far above what a normal being can take : you should not drink more than 1 liter of water per hour, because your kidneys can only remove that amount of water per hour.
If you drink too much water (> 90ml/kg is LD50, the dose 50% of people won't survive, so for a normal adult of 70kg we're talking 6,5 liters of water as fast as you can chug it in), the electrolyte balance in your nervous system will reverse, eventually resulting in the depolarization of all axons. Since this doesn't occur at all places in the nervous system simultaneously it will be a very painful and extremely scary way to die.
Anyway the doses the GP mentioned are enough to create issues (anything > 1L/hour creates issues, and a sustained water intake of more than 1L/hour will eventually kill you)
If you drink ~19 litres (5 US gallons?) of water every day you will not survive long. That’s about an order of magnitude more than is recommended under normal non-strenuous conditions.
I assume they were talking about supplementation at normal supplementation levels, not 10x - 100x that.
As someone pointed out below, if you drink 10x-100x the recommended amount of water, you're likely to have adverse effects (almost certainly including death at 100x) too.
Interesting fact - a healthy person's kidneys can excrete 25 litres of water a day. Drink more than this, and you expand your total body water volume to dangerous levels, which can lead to swelling in soft tissues and lungs (which can be life threatening). This happens in patients with psychogenic polydipsia.
Of course, drinking anywhere near 25L is not 'safe' either, and can still cause electrolyte abnormalities, neurocognitive dysfunction, seizures... Stick to the recommended intake, adjusted for water losses during significant exertion or high temperatures.
You can over-hydrate though. The myth that you need tons and tons of water has actually led to over-hydration which can cause serious problems or even death. https://en.wikipedia.org/wiki/Water_intoxication
> The article also says there is no downside to your health for drinking more.
You can poison yourself by drinking too much water. Can happen amongst very fit people doing a lot of exercise who think this means they have to down 10 litres of water in half an hour.
Sure, you can over-hydrate, but when is the last time someone died from drinking too much water who hadn't also just run a marathon? Referring to a normal person who decided to up their water intake, and died later that day?
Exercising in hot weather requires drinking electrolyte water to avoid hyponatremia. Drinking large amounts of soft or distilled water (around 6 liters) can lead to death.
I drank something between 4-6 liters of water in a couple of hours time last summer, and ended up with fever and throwing up excessively for the remainder of the day. I was more or less knocked-out for the next couple of days. So I can definitely tell you that drinking too much fresh water in a short time frame is anything but healthy...
I looked into one of the references...they put 120mg/L in mice and found it to be bad. Drinking water has about 0.7 mg/L. This is a factor of nearly 200x on concentration and another lot on body mass. Shoot, if I drink 200x more water that will cause problems too!
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