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Do you really need eight glasses of water every day? Do you really need to carry bottled water around like it was an extension of your arm? Here are the facts about ten common myths about hydration.

What do you think about your drink? Is what you have heard about hydration more hype than fact? Here are ten common myths about the human body's water needs and the facts that correct them.

Myth 1. Everybody needs the eight glasses (4 liters) of water every day.

There is no scientific basis of any kind for the often-quoted recommendation that everyone needs eight glasses of water every day. A study of stomach cancer in Asia found that the benefits of additional hydration are statistically significant at 5 cups (1200 ml) of water per day, that is, if you get at least that much water (and, in the Asian study, if you are male), then you are less likely to get stomach cancer. No claims for the health benefits of drinking more than that are to be found in the scientific literature. The Dietary Reference Intakes from the National Academies of Sciences, Engineering and Medicine’s Health and Medicine Division recommend 13 cups (a little over 3 liters) of total beverages for men and nine cups (a little over 2 liters) of total beverages for women as the average adequate daily intake for proper hydration in temperate climate. But heat, physical activity, infection, and salt intake can necessitate greater intake, just not as much as 4 liters of just water every day.

Myth 2. You need to drink before you get thirsty.

If you have ready access to water and other beverages, there is no need to play camel to make sure you don't get dehydrated. Your sense of thirst will let you know when you need to drink something. There are a couple of exceptions to this rule. If you working outdoors, or doing heavy exercise outdoors, in hot weather, then, yes, you do need to stay a little ahead of your thirst. Some older people may have a compromised sense of thirst and may need to make double sure they get enough to drink every day to avoid dehydration. Most of us, however, can wait until we feel thirsty.

Myth 3. The best way to rehydrate is with a sports drink.

It's absolutely true that muscles that have been worked out to the max need a combination of amino acids, glucose, electrolytes, and water to rebuild themselves and grow stronger. It's also true that a sports drink provides those nutritional needs very efficiently for people who have been physically active for at least an hour at a time. However, it's not true that you need a sugary sports drink every time you get sweaty from activity in the heat. Water and just a little fruit or fruit juice (10 grams/ one-half ounce of fruit or 30 ml/ one-eighth cup is enough) is all you to prevent dehydration in adults unless you have been working out very hard. Distilled water is never an optimal choice for rehydration.

Myth 4. Dark urine is always the most important of all dehydration symptoms.

This myth is wrong on two counts. Many other issues can cause dark urine, including liver and kidney diseases. Also, in heat stroke, there can be a phase in which large amounts of clear urine are passed, followed by dark urine, followed by no urination at all. Sometimes what is needed is more fluid, sooner, especially when small children become dehyrated. Sometimes drinking a lot of water only obscures a liver or kidney problem.

Continue reading after recommendations

  • Hoffman MD, Bross TL 3rd, Hamilton RT. Are We Being Drowned by Hydration Advice on the Internet? Phys Sportsmed. 2016 Aug 22:1-6. [Epub ahead of print] PMID: 27548748.
  • Stookey JD, Constant F, Popkin BM, Gardner CD. Drinking water is associated with weight loss in overweight dieting women independent of diet and activity. Obesity (Silver Spring). 2008 Nov.16(11):2481-8. doi: 10.1038/oby.2008.409. Epub 2008 Sep 11.
  • PMID: 18787524
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