LONDON: The two-litres-a-day mantra has recently been challenged by a number of respectable sources. Professor Heinz Valtin (who drinks just one glass of plain water a day, plus about five glasses of juice, coffee, milk and other fluids) is a kidney specialist and professor emeritus of physiology at Dartmouth Medical School in New Hampshire, America. He is the latest scientist to contest what is known in the US as the 8 x 8 recommendation (eight eight-ounce glasses of water daily).
Valtin spent ten months searching medical journals and databases for evidence supporting the claim, and wrote a report in the American Journal of Physiology in which he stated, “Despite the seemingly ubiquitous admonition to drink at least eight 8oz glasses of water a day, rigorous proof for this counsel appears to be lacking.”
Valtin says he isn’t questioning the crucial role water plays in the human body, but the issue of where it comes from. “I accept that the human body has certain daily fluid requirements, amounting to two-2.5 litres per day. I’m merely contesting the belief that this amount must all be consumed as fluid; much of it can, and does, come from the solid food we eat.”
Professor Ron Maughan, a physiologist and prolific researc-her of fluid intake at Aberdeen University, in Scotland, agrees: “Water comes in many forms, not just bottles and glasses. If you ate a large slice of watermelon, the amount of fluid you’d need to consume would be dramatically reduced.” Many foods, such as fruit and veg, are high in water, but even those that appear dry, such as bread, contain substantial amounts of water. In fact, at least a third of our daily fluid requirements are met through solid food.
It’s tempting to assume that the “two-litres-a-day” recommendation has been promoted by bottled water manufacturers to increase sales, but it’s more likely to be a case of misinterpretation. Data published by the US Food and Nutrition Board in the 1980s recommended one millilitre of water for each calorie of food consumed (equating nicely with the two-litres-a-day guideline). It went on to say that “most of this is contained in prepared foods”. Valtin believes that this last sentence has been erroneously disregarded. In his eyes, this has not only left a lot of people force-feeding water that they don’t want or need, but has also made them feel unnecessarily guilty about not achieving the daily target.
If you already drink two litres a day or more, and insist it makes you feel, and function, better, should you worry? “If it works for you, that’s fine,” says Valtin. “A safe guideline is to follow your customary fluid intake and your thirst; if you are healthy and producing urine of a moderately yellow colour, you should be all right.”—Dawn/The Guardian News Service.