Milk hydrates better than water, study shows.

What Beverages Keep You Hydrated?

When you’re thirsty, what do you reach for? While water is always a good choice, it may not be the most hydrating beverage out there. According to a study from Scotland’s St. Andrews University, drinks with a little bit of sugar, fat, or protein do a better job of keeping us hydrated for longer.

Milk: The Ultimate Hydrator

Believe it or not, milk is even more hydrating than water. It contains lactose, protein, and fat, which all help to slow the emptying of fluid from the stomach and keep hydration happening over a longer period. Milk also has sodium, which acts like a sponge and holds onto water in the body, resulting in less urine produced.

The same can be said for oral rehydration solutions used to treat diarrhea. These contain small amounts of sugar, as well as sodium and potassium, which can help promote water retention in the body.

Sugar in Moderation

While drinks with more concentrated sugars, such as fruit juices or colas, may spend more time in the stomach and empty more slowly compared to plain water, they are not necessarily as hydrating as their lower-sugar counterparts. Once these beverages enter the small intestine, their high concentration of sugars gets diluted during a physiological process called osmosis. This process “pulls” water from the body into the small intestine to dilute the sugars these beverages contain. And technically, anything inside the intestine is outside your body.

Juice and soda are not only less hydrating, but they also offer extra sugars and calories that won’t fill us up as much as solid foods. If the choice is between soda and water for hydration, go with water every time. After all, our kidneys and liver depend on water to get rid of toxins in our bodies, and water also plays a key role in maintaining skin’s elasticity and suppleness. It’s the cheapest moisturizer you’ll find.

Can Beer and Lattes Keep Me Hydrated?

When it comes to alcoholic beverages, hydration will depend on the beverage’s total volume. Alcohol acts as a diuretic, which causes you to pass more urine. “Beer would result in less water loss than whiskey because you are ingesting more fluid with beer,” says Ronald Maughan, a professor at St. Andrews’ School of Medicine and the study’s author. “Strong alcoholic drinks will dehydrate, dilute alcoholic drinks will not.”

As for coffee, how well your java hydrates you will depend on the amount of caffeine you consume. A regular coffee with about 80 milligrams of caffeine would be pretty much as hydrating as water, according to Maughan’s research. Consuming more than 300mg of caffeine, or about 2-4 cups of coffee, could cause you to lose excess fluid as the caffeine causes a mild, short-term diuretic effect. This is more likely to happen with someone who doesn’t typically consume caffeine, and it could be offset by adding a tablespoon or two of milk to your cup of joe.

While staying hydrated is important, in most situations, people don’t need to worry too much about how hydrating their beverages are. “If you’re thirsty, your body will tell you to drink more,” says Maughan. But for athletes training seriously in warm conditions with high sweat losses, or for someone whose cognitive function may be negatively impacted by working long hours without beverage breaks, hydration becomes a critical issue.

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