Water, Water Everywhere – How Much Do We Need?

Let’s clear this up right now. There is no need to guzzle 8 big glasses of water a day. You’re already getting most of that in the food you eat.
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The very idea of a "minimal water requirement” is a notion from 1945 published by the British Food and Nutrition Board of the National Academy of Sciences. They came up with – without a single bit of evidence – the spurious quantity "2,500 mL [2.5 liter, 10 cups] of fluid” that everyone should ingest daily. [1]

The myth was debunked in a 2011 article in the British Medical Journal, by Margaret McCartney who pointed out that one water advocacy group in Europe, was actually created by food giant Danone, who owns Evian among other bottled waters. [2]
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But health guru types  - who rarely read actual science papers - had already swallowed the lie and proceeded to parrot it to the world. So, everyone, I included, ran out and bought oodles of plastic bottles of water, which ended up in landfills, the ocean and everywhere else they don’t need to be.
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Most everything we eat contains water. For example, iceberg lettuce is 96% water, a broiled pork chop is 71% water, and a baked potato is 58%. So, if you calculate the meals you eat, you’ll see that you consume plenty of water without drinking 8 glasses.
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Let’s try it out and calculate the water in a typical day’s meals. The weight and percentage of water in each of the following foods is from the very comprehensive USDA’s Nutritive Value PDF: https://tinyurl.com/USDAARSNutripdf. [3]
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To make the conversion from grams to milliliters I had to take each food’s physical density into account. The information on food densities can be found in the UN’s report FAO / Infoods Databases.” [4]

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If you eat this menu in a day, you’ve already consumed 4.68 cups of water; you only need to drink 3.32 more cups to reach the “required” amount of water recommended by all the idiot diet gurus. Of course, no real scientists suggest that anymore. They are more likely to suggest that you listen to your own body.

Our bodies give us plenty of information about hydration. It’s called thirst. When I feel thirsty, I drink.

Admittedly, keeping a bottle of water handy to sip from can prevent the mindless noshing that puts weight on; thirst can sometimes masquerade as hunger. And if you’re physically working or playing hard or if you’re out in the sun, you’re going to need a little more.

​But nobody needs 8-10 glasses of water a day.

REFERENCES
​[1] Chris Gayomali, “Where Did the 8-Glasses-of-Water-a-Day Myth Come from?,” The Week (The Week, September 16, 2015), https://tinyurl.com/theWeekWaterMyth
[2] Margaret McCartney, “Waterlogged?,” The BMJ (British Medical Journal Publishing Group, July 12, 2011), https://www.bmj.com/content/343/bmj.d4280.
[3] Joyce Cox, “Nutritive Value - USDA ARS,” Agriculture Research Service (US department of Agriculture, September 30, 2002),  https://www.ars.usda.gov/is/np/NutritiveValueofFoods/NutritiveValueofFoods.pdf.
​[4] U. Ruth Charrondiere, David Haytowitz, and Barbara Stadlmayr, “FAO / Infoods Databases,” Food and Agriculture Organization of the United Nations (United Nations, 2012), https://www.fao.org/3/ap815e/ap815e.pdf.

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