Is Milk More Hydrating Than Water?

Sunrise Senior Living  |  July 20, 2016
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Water isn't your only source for proper hydration.

Staying properly hydrated is important, but it's especially crucial during the summertime. By keeping your body hydrated, you're helping your heart pump blood through the blood vessels to reach the muscles effectively, according to the American Heart Association. Essentially, proper hydration keeps your heart from working too hard.

While the U.S. Centers for Disease Control and Prevention said most needs are met through water, that's not the only source you can use for hydration. In fact, there's a "beverage hydration index" that shows evidence that plenty of other options can hydrate your body just as well as water - if not more.

The study
The researchers from Loughborough University, created the index investigating 13 popular beverages. These liquids consisted of water, an oral rehydration solution, full-fat milk, skimmed milk, cola, diet cola, hot tea, iced tea, coffee, lager, orange juice, sparkling water and a sports drink. 

The subjects consisted of 72 euhydrated - defined as someone with the normal state of body water content - and fasted males, who began by drinking one liter of water. The researchers noted the amount of water remaining in each subject's body after two hours and assigned it a score. The same analysis was performed on every other beverage and then compared to the water. The scores determined their beverage hydration index.

The results
The researchers found that the oral rehydration solution, orange juice, full-fat milk and skimmed milk were higher on the hydration index than water. But what makes both milks such excellent sources of hydration? Ronald J. Maughan, lead author of the study told the New York Times that it's all about the nutrients contained in the liquid.

"Normally when you drink, it signals the kidneys to get rid of the extra water by producing more urine," he said. "However, when beverages contain nutrients and electrolytes like sodium and potassium, as milk does, the stomach empties more slowly with a less dramatic effect on the kidneys."

As for the other beverages tested, each one had the same response to water ingestion. So despite popular belief, coffee and beer are not dehydrating liquids. The cola and sports drink can also hydrate you, but they're not recommended as your go-to source due to high sugar content. 

The take away
This beverage hydration index provides vital information about which liquid you should consider for proper hydration. The Times reported that this data can be especially useful for those who need to make decisions on beverages for certain situations, such as a long drive or another moment when you don't have immediate access to an abundance of fluids. In this case, choosing milk over water is the better decision.