|Written by Tracy Trumper|
Fact or fiction: Drink 8 glasses of water daily
90 degrees, 95 degrees, 100 degrees—the temperatures are reaching the typical summer highs. What do studies show about proper hydration for health?
According to the Tufts University Health and Nutrition Letter’s Special Report, there is little scientific evidence confirming that eight glasses of water should be the daily requirement. Body size, energy expenditures through exercise or work and other factors can cause actual fluid needs to vary among individuals.
The 1945 finding that people needed 64 ounces, or eight 8-ounce glasses, of fluid a day is probably where the “eight glasses a day” myth originated. The key that still is supported today is that the recommendation states “fluid,” not just water per day.
So this “fluid” includes fluids in foods as well as coffee, tea, juice and soda. Fluid content in food accounts for up to 22 percent of the average American’s water intake.
Studies have shown that even caffeinated beverages that can have a diuretic effect should not be canceled out as having hydration benefits. However, these types of beverages are also high in calories, contributing to obesity.
A 2002 study at Dartmouth Medical School and a 2008 review in the Journal of the American Society of Nephrology both concluded that there is no scientific proof for the “eight glasses a day” rule of water intake.
So how much is enough? Water is very important for the body as it carries nutrients and oxygen throughout the body and carries waste away. Every cell in the body needs water for proper function.
Seventy-five percent of the body weight of infants is water, and about 55 percent in elderly. So there is knowledge about the importance of water for proper body function and how much of the body is water, but there is little known from controlled scientific study about how additional water in hydrated individuals offers any more benefit.
Consequently, “fluid intake, driven by thirst … allows maintenance of hydration status and total body water at normal levels,” according to the Institute of Medicine.
The elderly might need to pay more attention to the body’s hydration needs, as older people often have a reduced sensation of thirst, putting them at risk for dehydration.
Older individuals tend to drink less fluid and have lower reserves to replenish the system from a water deficit. Also, the body’s internal thermostat is challenged in older adults because they sweat less.
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