Some quality research here on the highly controversial subject of hydration!
MYTH: Coffee/caffeine is a diuretic, dehydrating rather than rehydrating you Coffee contains caffeine, which has a weak diuretic (water-losing) effect if you normally avoid caffeine. If you regularly consume coffee, tea, chocolate or energy drinks (such as Red Bull), your liver learns to process caffeine quickly, neutralising this effect. Research shows the key factor influencing the diuretic effect of coffee is not related to its caffeine content but to the size of the drink.
MYTH: We should all drink two litres of water a day Research in the Forties found adult men needed two litres of fluid a day to stay hydrated. But this includes water content of food, which is more significant than you may imagine. Even toasted bread is a quarter water. The amount of fluid needed depends on activity and body size. If you are hydrated, you will produce a decent amount of urine, the colour of light straw, two to three times a day. Any excess just passes out. You don't get extra benefit from drinking more than you need.
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