How to calculate how much water you should drink
umsystem.edu
umsystem.edu
This is a common misunderstanding around those "you need X glasses of water per day" recommendations -- much (sometimes, most) of your needed water comes in your food and doesn't need to be consumed as a separate thing.
And even though there are other health considerations to them, water you take in the form of coffee, tea, soda, etc., also counts.
https://journals.physiology.org/doi/full/10.1152/ajpregu.003...
Woo + math == woo
Our thirst system is as precise and robust regarding water as our pancreas is for glucose.
If I only drink when I'm thirsty, then half the time I'll be depressed and headachey and unfocused and not thirsty until I idly grab a drink and suddenly find myself standing in front of the sink chugging three glasses of water.
If your thirst system is finely tuned, that's nice for you. I and millions of others could use a better system.
Thirst is an early'ish warning, but not early enough if you've eaten food that needs more water in order for your body to process it than you have consumed prior to eating, or you have diarrhea, or you are low on electrolytes, or your kidneys have problems monitoring and maintaining the balance of said electrolytes.
See also:
I'd say "Drink when you are thirsty".
I learned this the hard way on the third day of my first such trip, when my urine had become brown due to dehydration.
Note that while your thirst response may be declining as you age, mine hasn't.
Annicdodes aren't data, mine or yours.
IMHO the 8x8 myth may or may not be optimal guidelines for you as they aren't based on anything but rumors.
> Several studies have demonstrated that elderly persons have lower total water intakes than younger adults, and that women are particularly at risk of too low an intake.
I know this is anecdotal, but I've heard so many people tell me that they skip meals because they simply "forgot to eat." Do you think those people remembered to drink water? I don't think so.
So, yes, people tend to be terrible at noticing what they need, and when they do notice they are terrible about doing something about it.
I often heard really exaggerated advice about how much water to guzzle every day. It got crazy.
One day several years ago, a nurse was taking vitals on me and told me to drink, I don't know, 48 cups per day or something? It was huge. And I regarded her with incredulity. So upon being taken in to see the doctor, and this was a physician that I really trusted and had a good long tenure, I repeated the advice and I said, "That's BS, right?" and she said yep, and I'll talk to that nurse...
I am especially wary of my fluid intake because I live in an urban desert. Therefore I must constantly drink fluids when it's hot to stay healthy and hydrated. However, I must also gauge my ability to find a bathroom while out on the road, and when you ride the bus, good luck with that! It might be 3 hours, or you're forced to make a small order at a restaurant to become a customer. So it's really a delicate balancing act of how much to drink. And also, remembering to use the bathroom at every opportunity!
That sounds like enough water to actually be harmful/deadly, especially depending on what "cups" means there.
It makes me wonder how some people don't seem to recognize, that we as a species have been on this planet for quite some time now, and that IS the greater part of out existence on this planet when compared to how long we've studied science and medicine of today!
The timeline of either is heavily weighted on the side absent of anything we would call "modern." :-)