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The question

How much water should I drink in a day?

The answer

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What seems like a simple question doesn't have a straightforward answer. While many experts recommend eight or more glasses a day, others contend you need to drink water only when thirsty.



Water is essential to your health. Water makes up roughly 60 percent of our body weight. It's needed to regulate body temperature, transport oxygen and nutrients to cells, flush toxins from organs, keep your skin moist and cushion your joints. Drinking enough water also helps keep kidneys healthy by flushing away chemicals that form stones.



The most recent dietary recommendations, published by the U.S. based Institute of Medicine in 2004, state that men should drink three litres (13 cups) of water each day and women need 2.2 litres (nine cups). Children, aged one to three years, need one litre (four cups) daily . Children, four to eight, require 1.3 litres (5.5 cups). Teenagers need to drink more - about 1.8 litres (seven cups) for girls and 2.6 litres (10.5 cups) for boys.



These guidelines don't apply if you engage in moderate or vigorous exercise and they don't account for hot weather, two factors that drive up the body's need for water. Women who are pregnant need an additional one cup (250 ml) of water each day; breastfeeding women require an extra four cups (one litre).



This might sound like a lot of water, until you consider that everything you drink - excluding alcoholic beverages - counts toward your daily water requirements. Once you factor in coffee or tea, fruit juice at breakfast, milk on cereal, sports drinks, even soft drinks, you're probably doing better than you think.



(Alcohol is a diuretic, meaning it causes your body to lose water. Caffeine has a relatively mild diuretic effect that appears to diminish with daily consumption.)

Send dietitian Leslie Beck your questions at dietitian@globeandmail.com. She will answer select questions, which could appear in The Globe and Mail and/or on The Globe and Mail web site. Your name will not be published if your question is chosen.

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Read more Q&As from Leslie Beck.

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The content provided in The Globe and Mail's Ask a Health Expert centre is for information purposes only and is neither intended to be relied upon nor to be a substitute for professional medical advice, diagnosis or treatment.

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