Drinking the recommended eight glasses of water a day may be too much for our actual needs, according to scientists.
Given that about half of our daily water intake comes from food, researchers estimate we only need about 1.3 to 1.8 liters a day, instead of two.
Previous studies in this area relied on surveys conducted on small samples of people, but more than 90 scientists around the world have now collaborated to measure water turnover using a different technique.
Given that about half of our daily water intake comes from food, researchers estimate we only need about 1.3 to 1.8 liters a day, instead of two
They surveyed 5,604 people aged between eight days and 96 years from 23 different countries.
The participants drank a measured amount of water enriched with the element deuterium, which occurs naturally in the human body and is completely harmless.
They measured the rate at which the deuterium disappeared from the body, showing how quickly the water was circulating in the body.
An analysis published in the journal Science found that people living in hot and humid environments and at high altitudes, as well as athletes, pregnant and lactating women needed more water because their turnover was higher.
Professor John Speakman, one of the authors from the University of Aberdeen, said water turnover does not match drinking water needs.
“Even if a man in his 20s has an average water turnover of 4.2 liters per day, he doesn’t need to drink 4.2 liters of water every day,” he said.
“About 15 percent of this value reflects surface water exchange and water gained from metabolism.
“The actual water intake required is about 3.6 liters per day. Since most foods also contain water, a significant amount of water is provided by eating alone.
“This study shows that the general recommendation that we should drink every eight glasses of water is probably too high for most people in most situations.”
Drinking the recommended eight glasses probably isn’t harmful, he explained, but it’s also not necessary in most cases.
“Calculations suggest that a typical middle-aged man needs to drink around 1.6 to 1.8 liters per day and a typical woman of the same age around 1.3 to 1.4 liters,” he said.
“For people in their 80s, that could drop to about 1.1 liters a day.
“But it depends a lot on what types of food they eat. For example, if they drink a lot of soup, they should drink less.”
Tea, coffee, fizzy drinks and fruit juices also count towards the daily total, he said, but they also include other things that may not be healthy.
Co-author Dale Schoeller of the University of Wisconsin-Madison said: “Science has never supported the old eight-glass thing as a reasonable guideline, if only because it takes total water turnover from water from beverages and a majority of your water.” confused comes from the food you eat.
“But this work is the best we’ve done to measure how much water people actually consume each day — the water turnover in and out of the body — and the key factors that drive water turnover.”
It comes after doctors this week claimed kung fu legend Bruce Lee may have died from drinking too much water.
The martial arts star and Hollywood icon died in 1973 at the age of 32.
Doctors ruled that his death was due to brain swelling, which was attributed to taking a painkiller.
His death sparked rumors that he might have been murdered by Chinese gangsters, poisoned by a lover, or the victim of a curse.
Researchers reviewing the evidence decided that Bruce probably died from hyponatremia.
“In other words, we suspect the kidney’s inability to eliminate excess water killed Bruce Lee,” experts wrote in the Clinical Kidney Journal.
WHAT SHOULD A BALANCED DIET LOOK LIKE?
Meals should be based on potatoes, bread, rice, pasta or other starchy carbohydrates, ideally whole grain, according to the NHS
• Eat at least 5 servings of varied fruit and vegetables daily. All fresh, frozen, dried and canned fruits and vegetables count
• Base meals based on potatoes, bread, rice, pasta or other starchy carbohydrates, ideally whole grains
• 30 grams of fiber per day: This equates to eating all of the following: 5 servings of fruit and vegetables, 2 whole wheat biscuits, 2 thick slices of whole wheat bread, and 1 large baked potato with its skin on
• Have some dairy products or dairy alternatives (like soy drinks) and choose lower-fat, lower-sugar options
• Eat some beans, legumes, fish, eggs, meat and other proteins (including 2 servings of fish per week, one of which should be oily)
• Choose unsaturated oils and spreads and consume them in small amounts
• Drink 6-8 cups/glasses of water daily
• Adults should consume less than 6g of salt and 20g of saturated fat for women or 30g for men per day
Source: NHS Eatwell Guide