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So, I try to drink a decent amount of water. But I can't drink anywhere near 2 litres a day (which apparently is the recommended daily intake).

I do drink quite a few cups of coffee. And I'm aware that, contrary to belief, cups of coffee do actually count as water intake.

But drinking 2 litres is just too much. Which leads me to wonder if the vast majority of people are not getting enough water.

I really think most people don't drink even half a litre of water a day, never mind 2 litres.

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  • I take 4 L of mostly water. May 13 '18 at 14:57
  • @Blacksmith37 Wow. You literally drink 4 litres of water a day? Do you wee a lot, may I ask? And do you not feel bloated? May 13 '18 at 14:59
  • 1
    @blacksmith37 & White Pine - Anecdotal experiences and medical advice are off topic here. The only valid answers to this question will be if someone can find research showing how much water "most" people drink.
    – Carey Gregory
    May 13 '18 at 15:05
  • @Carey Gregory Apologies, mate. May 13 '18 at 15:06
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In short: It may not be possible to recommend any fixed amount of water to anyone, because the water needs differ from person to person, and for a given person, from day to day, which mainly depends on the extent of sweating.

According to Dietary References for Water, National Academic Press (p. 80, Table 4-2), an estimated minimal loss of water (when not sweating) in a healthy adult is ~1 liter per day, so this is the minimal amount of water one should consume (from foods and beverages combined).

Dehydration and Rehydration, Defense Technical Information Center:

The daily water needs of sedentary men are ~1.2 L or ~2.5 L and increase to ~3.2 L if performing modest physical activity. Compared with sedentary adults, active adults who live in a warm environment are reported to have daily water needs of ~6 L.

According to Mayo Clinic, you can know you are well hydrated when:

  • You are not thirsty.
  • Your urine is clear or straw yellow.
  • You maintain your usual body weight from day to day (for example, 2 liters water loss results in 2 kilograms or 4.4 pounds of body weight loss).
  • The skin at the back of your hand recoils instantly when you pinch and release it (skin turgor test, MedlinePlus).
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  • Excellent answer to a different question. The question was: Do people actually drink 2 L per day? This doesn't answer that.
    – Carey Gregory
    May 15 '18 at 0:49
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I think most people do not drink a such quantity of water. Think: 2 litres are more or less equal to 8 glasses, but on average we have: 2 for breakfast, 2 for lunch, 2 for dinner [ 1 ], that's just above 1 litre of water.

I think your thought is true: it's hard to drink 2L of water.

Anyway I think (but I don't have any refs...) people intake (drink+eating) more than 2L of water. If we take in account eating vegetables and fruits (90% w/w of water if raw, less if cooked) as well meat and fish (70% w/w cooked), we reach the goal of 2L of water per day.

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  • When you actually fill a 2 litre bottle with water, though, Mattia, there's a very large amount of water there. May 13 '18 at 13:39
  • 2
    Welcome to Health.SE. Since health is an important topic, the site has a strict policy that all answers should be backed up with reliable references so that the answer can be independently verified, regardless of the reader's background. See this list of reliable sources. If you still have trouble with this, feel free to visit the help center or Medical Sciences Meta.
    – Carey Gregory
    May 13 '18 at 15:02
  • 1
    edited the answer to reflect the policy
    – mattia.b89
    May 14 '18 at 17:58
  • Downvote retracted and upvoted also. :-)
    – Carey Gregory
    May 15 '18 at 0:47
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We can find the answer here:

Among U.S. adults, men consumed an average of 3.46 liters (117 ounces) of water per day, and women consumed 2.75 liters (93 ounces) per day. Men aged 60 and over consumed less water (2.92 liters) than men aged 20–39 (3.61 liters) and 40–59 (3.63 liters). Similarly, women aged 60 and over consumed less water (2.51 liters) than women aged 20–39 (2.78 liters) and 40–59 (2.9 liters). Non-Hispanic white men and women consumed more water daily than non-Hispanic black and Hispanic men and women. Water intake increased with physical activity level for both men and women. Among men, 30% of total water consumed was plain water (with the remainder from other foods and liquids) compared with 34% for women.

So, the intake of plain water is about 1 liter, but people also drink other liquids like e.g. soft drinks that are not counted as plain water (e.g. the average soda intake is about 0.5 liters per day). As the article points out, the adequate total water intake from all foods and liquids has been set at 3.7 liters by the Institute of medicine (IoM), so the average intake falls short of the adequate intake. So, most people would benefit from a higher plain water intake, they would get closer to the IoM recommended intake and it would likely come at the expense of unhealthy soda intake.

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  • Adequate intake (AI) 3.7 liters per day CANNOT be interpreted as a recommendation for personal use. AI is an estimation according to which, 3.7 liters of water meets the needs of most sedentary adult men living in temperate climates. So, 3.7 L is only for those with the highest needs within this group and not for everyone. This is like saying if some athletes need 5K Calories per day then everyone needs 5K Calories. According to Mayo Clinic: "For some people, fewer than eight glasses [2 L] a day might be enough. But other people might need more."
    – Jan
    May 15 '18 at 7:12

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