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Technically it's 8 glasses of fluid a day, not just water.


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8 glasses of water a day

>The well-known “8 x 8” rule — you should drink eight 8-ounce glasses of water a day — is not only daunting, it’s unfounded. In fact, nobody is sure where the idea came from, and science doesn’t support it. “It has no basis in fact,” says Michael Farrell, a professor at Monash University in Australia, who studies how the brain responds to thirst and other sensations.

> The average adult woman should consume about 11.4 cups of fluid per day (a cup equals 8 ounces) and men should consume 15.6 [...] Subtracting the 20% of water consumed through food, that means the average woman should drink about 9.1 cups of fluid daily, and a man should drink about 12.5.

8 times 8 ounces per day of fluid is 64 ounces of fluid per day, whereas ~9 cups per day of fluid times 8 ounces/cup is ~72 ounces of fluid per day. So isn't the recommendation actually _more_ than the 8x8 adage?


Aldo respect, this article is a waste of time. We're so obsessed with putting a number on everything - that's why the "8 glasses a day" rule exists. It's not literal. It means "drink a lot of water throughout the day and you'll feel better." Which is true. I drink tons of water and it's made a massive difference in every aspect of my life. I have no idea how much I drink daily, though. It doesn't matter. Because we're all different. Just drink more water, and stop trying to figure out that magic number by reading articles from the media that change every week.

No, you don't have to drink 8 glasses of water, nor 2 nor 12, you have to drink what your body needs and asks for

I believe 8 glasses came from a study that said we need approx. 8 glasses of water per day from all source, e.g. including food. But media outlets spread this as we should drink 8 glasses day and it stuck ever since.

The widely accepted notion that we should drink 8 glasses of water per day is apparently an urban legent

http://www.snopes.com/medical/myths/8glasses.asp


The point is that the 8 glasses of water a day thing is bullshit. I see people carrying giant jugs of water around all the time and people commenting on basically forcing this on themselves. Drink when you're thirsty. That's all you need to do.

FYI, that "recommended dose" of eight glasses a day is mythical. No scientific basis whatsoever. If you aren't thirsty, you're drinking the right amount of water.

http://www.snopes.com/medical/myths/8glasses.asp


Or maybe “four to eight” cups. The idea of drinking almost 12 liters of water each day is pretty amusing.

Reasonable person: 8 glasses of water keep you healthy.

You: WHY DON'T YOU DRINK 100 LITERS A DAY IF YOU LIKE IT SO MUCH!!


The distinction is between “8x8 glasses of water, independent of all other fluids you ingest” pseudoscientific rule, and “9.1 - 12.5 glasses of non-alcoholic fluids, which includes juice, milk, coffee, tea, etc, not just water”

Drink 6 cups of coffee, a glass of OJ, and 2 glasses of water would be just fine for an adult Woman, but the “rule” convinces people they’re still falling 6 glasses short of water.


I drink at least 4L of fluid on a normal day. For what you describe I'd probably double it.

What is the conclusive evidence against drinking 8 glasses of water a day?

> Even the 8 glasses a day of water suggestion is considered on the high side and that’s only 1.9L.

The recommended amount depends on who does the recommendation but 1.9L doesn't seem high.

https://www.efsa.europa.eu/fr/efsajournal/pub/1459

"Adequate Intakes (AI) have been defined derived from a combination of observed intakes in population groups with desirable osmolarity values of urine and desirable water volumes per energy unit consumed. The reference values for total water intake include water from drinking water, beverages of all kind, and from food moisture and only apply to conditions of moderate environmental temperature and moderate physical activity levels (PAL 1.6). [...] Available data for adults permit the definition of AIs as 2.0 L/day (P 95 3.1 L) for females and 2.5 L/day (P95 4.0 L) for males."

https://apps.who.int/iris/handle/10665/43403

"The minimum water requirement for fluid replacement for a 70kg human in a temperate zone equates to 3L per day, or 42.9mL/kg [according to the Tropical Agriculture Association]. Minimum requirements for an individual the same size but in a tropical zone equates to 4.1 to 6L/day"

"Age and gender specific Adequate Intakes (AI) for water were established in 2004 by the [United States] Food and Nutrition Board (5). The Dietary Reference Intakes (DRI) for water are [for ages 19 and older] Men 3.7 L/day Women 2.7 L/day"


> quite a few people don't actually hydrate enough during the course of a day

Do you have some cites for this? I've heard some of the dumbest damn things about water (like the 'eight glasses a day' myth) and it's hard to keep them all straight.


What people often take away from that is that they should drink eight glasses of water _in addition to_ everything else they might consume--soda, juice, coffee, and anything else that has water in it. And they think there's a rule they need to adhere to, and not trust the fact that our bodies are actually pretty good at letting us know when we need water.

Are you drinking 4-8 litres a day?

Don't hold me to this, but if I recall, the recommendation is to consume 8 cups (1 cup = 8 oz ˜ 0.23L) of water a day, and the water contained in our food counts. This is to say, people conflated 8 cups of water to mean 8 glasses of water.

Just remember, 8 cups of water a day is a myth. It has no scientific basis[0].

It was the result of misunderstanding a 1945 study that spread around like wildfire (since people realised they weren't drinking 8 cups, and tried to). The figure includes water contained within food, which is a significant amount. If you're drinking 8 cups AND consuming a normal diet you may be drinking too much (assuming moderate weather conditions and no underlying medical problems leaving you dehydrated).

[0] http://www.bmj.com/content/335/7633/1288

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