We’re all familiar with the recommendation to drink eight, 8-ounce glasses of water each day (commonly expressed as “8 x 8”). Other drinks — coffee, tea, soft drinks, beer — don’t count.
This exhortation is everywhere: from writers, nutritionists and dietitians, and doctors. And we slavishly follow it, carrying bottles of water everywhere, constantly sipping from them.
Nobody is arguing against the fact that water is good for you, but the ubiquitous recommendation to drink at least 64-ounces of water per day is unsubstantiated.
The 8 x 8 Rule
The source of the 8 x 8 is anyone’s guess, however, one theory suggests this rule originated in 1945 when the Food and Nutrition Board recommended that people need 2.5 liters of water a day.
But people failed to read the following sentence which read, “Most of this quantity is contained in prepared foods,” and the recommendation was therefore erroneously interpreted as eight glasses of water should be consumed each day.
All foods, including crackers, contain water which accounts for about 20 percent of people’s total water intake. In addition to soups or broths, fruits, vegetables, and animal products contain the highest amounts of water.
For example, watermelon and zucchini are more than 90 percent water, and four ounces of broiled salmon provides about one-half cup of water.
And while water is the preferred beverage, other drinks like juice, soda, milk, tea and coffee contribute to hydration needs. Contrary to belief, research shows that coffee and tea, despite their caffeine content, do not lead to dehydration and provides similar hydrating qualities as water.
Health Benefits of Water
Just like there is no substantial evidence that you need to consume eight, 8-ounce glasses of water each day, there is no compelling evidence that, for otherwise healthy people, drinking more water has extra health benefits.
For example, research reviews have failed to find evidence suggesting that drinking six to eight glasses of water keeps skin hydrated, makes skin look healthier or prevents wrinkles.
In fairness, some epidemiological research have found increased water to be associated with improved health outcomes. These studies, however, are subject to inherent weaknesses such as the inability to prove causation. Additionally, a “high” water consumption was defined as much less than eight glasses.
Research also fails to find benefits in kidney function when healthy people increase their fluid intake. In specific cases, randomized controlled trials find increased fluid intake beneficial for preventing the recurrence of some kinds of kidney stones.
Water Needs Differ
Comprising 60% of the body, water serves many vital roles. It regulates our body temperature, transports nutrients through our cells, and flushes waste from our bodies.
But there is no formal recommendation for the amount of water people need. The amount is influenced by a person’s diet, where they live, how much they weigh and what they are doing.
Let thirst be your guide. While many believe that thirst is an indicator that a person is already dehydrated, this claim is not proven by any research. The human body is designed to signal you need to drink well before you are dehydrated.