For many years I have thought that drinking eight glasses of water on top of your normal diet of food and beverages is illogical. I was a lone voice in the wilderness, but now I have an ally in La Trobe University lecturer Spero Tsindos (PhD, Dietetics and Public Health). Drinking eight glasses of water a day to stay healthy is a myth says Mr Tsindos, people can get their daily fluid intake from fruit, vegetables, juices and even tea and coffee.“We should be telling people that beverages like tea and coffee contribute to a person's fluid needs and despite their caffeine content, do not lead to dehydration."
Mr Tsindos believes that the 'eight glasses a day' notion may have stemmed from guidelines published in the US in 1945. The current Australian guidelines suggest an adequate daily fluid intake is about 2.8 litres for women and 3.4 litres for men. This does include fluid found in food and beverages and so I wasn’t quite a voice in the wilderness after all.
Looking a bit further I found that Heinz Valtin M.D. an emeritus professor at Dartmouth Medical School, published a report echoing the above statements in 2002 (American Journal of Physiology), and, in February 2004 the Institute of Medicine (IOM) issued new guidelines that removed the 'eight glasses a day' recommendation, stating that healthy adults may use thirst to determine their fluid needs. Obvious exceptions to this rule include anyone with a medical condition requiring fluid control, and people whose living conditions are extreme.
How much fluid is there in normal food? For every half cup of old fashioned porridge oats there is one and a half cups of water added. Fruit juice contains more than 80% of water. Tea and coffee contains over 95% of water depending how you drink it. For a comprehensive list of the water content of fruit and vegetables have a read of the list provided by the University Of Kentucky College Of Agriculture here.
Although beer has been used as a thirst quencher for centuries (most water was not safe to drink many years ago), I suggest that beer and other alcoholic drinks be taken in moderation. In the days of hand blown glass the artisans drank large quantities of beer and died early from liver complaints.