The Surprising High-Protein Drink That Might Be as Hydrating as Water

If you've ever felt extra-thirsty, even after chugging a tall glass of H2O, you're probably aware that water isn't the only hydrating beverage. Next time water just doesn't cut it, and you're feeling parched—like after a sweaty workout—try reaching for a cup of milk. Yes, we're talking real dairy milk.

Why Milk Can Help with Hydration

Dairy milk has the perfect hydrating trifecta of electrolytes, water and carbohydrates. This thirst-quenching combination makes milk a beverage that can help with hydration. And some bodies of research back this up.

While a bit older, a 2016 study in the American Journal of Clinical Nutrition found that out of 13 beverages tested, only whole milk, skim milk, an oral rehydration solution and orange juice were more hydrating than water. A small 2016 study in the British Journal of Nutrition found that skim milk hydrated people post-workout better than plain water and a drink with carbs and electrolytes. And another small study published in Applied Physiology Nutrition and Metabolism in 2014 found that skim milk hydrated kids and adolescents better than water or sports drinks after exercise. It’s important to note that these studies have certain limitations, including the sample size and diversity, meaning that more research is needed to support these findings. 

Here, dietitians explain the science behind what makes milk a good option for hydration.

It Has Electrolytes

Electrolytes are minerals, including sodium, potassium, calcium and magnesium. They help maintain our body’s overall balance, from regulating chemical reactions and helping our muscles contract to maintaining blood pressure and the right balance of fluid, says Katie Brown, Ed.D., RDN, president of the National Dairy Council. Regardless of its fat content, milk has you covered for all of these electrolytes. 

According to the USDA, one 8-ounce serving (1 cup) of reduced-fat (2%) milk contains:

• Calories: 122
• Carbohydrates: 12 g
• Dietary Fiber: 0 g
• Total Sugars: 12 g (naturally occurring)
• Protein: 8 g
• Total Fat: 5 g
• Saturated Fat: 3 g
• Sodium: 96 mg (4% Daily Value) 
• Calcium: 309 mg (24% DV)
• Potassium: 390 mg (8% DV)
• Magnesium:  29 mg (12% DV)
• Phosphorus: 252 mg (20% DV)

"While electrolytes don’t hydrate you per se, they help regulate your fluid balance and how well you hold on to or lose fluids," says Matt Pikosky, Ph.D., RD. "Without the proper balance of sodium, potassium and other electrolytes in your body, you can’t retain the water you’re drinking as effectively because sodium promotes fluid retention, which supports hydration and rehydration," he says.

It's 90% Water

Dairy milk, like many other foods, such as fruits and veggies, is naturally high in water content, which can help contribute to your hydration needs.  

"Milk naturally contains about 90% water, which can help hydrate us in a similar way that water hydrates," Pikosky says. 

Like all beverages, milk is primarily made of water, which is absorbed in your intestines and promotes hydration, says Melanie Betz, M.S., RD, CSR, FAND, founder and CEO of The Kidney Dietitian in Chicago.

But what makes milk a good option for hydration is the naturally present electrolytes. "Electrolytes help regulate fluid balance, making it a double dose of hydration," Pikosky says.

It Contains Natural Sugar

Sugar is a type of carbohydrate, and dairy milk contains a natural sugar called lactose.

"Any type of carbohydrate (like lactose) can help hydration because the process of absorbing carbohydrates in your intestines requires electrolytes," Betz says. 

"The presence of carbohydrates helps with fluid absorption from the small intestine into the bloodstream," says Pikosky. So carbs help those electrolytes get absorbed into your body, where they can help fluid go where it should.

What's more, "The carbs in milk also help to slow the digestion process, which can lead to a slower release and absorption of the water naturally present in dairy milk," Brown says.

And that all translates to better hydration levels.

Are Plant-Based Milks as Hydrating as Dairy Milk?

OK, so is stocking your fridge with oat or almond milk doing your body any favors? It's hard to say, for two reasons. First, there isn't much research on plant-based milks' role in supporting hydration; second, there are so many different types of vegan dairy milks available on the market, with widely varying nutritional profiles, that it's difficult to generalize. 

Still, the majority of plant-based milk alternatives don't offer the same nutritional profile as dairy milk, says Pikosky. 

What's unique about dairy milk is that it contains a natural balance of water, electrolytes and macronutrients (carbs, protein and fat). And "plant-based milks generally have less potassium and sugar than cow's milk—so, they may technically be less hydrating," Betz says.

If you're avoiding dairy or looking for a vegan alternative, the plant-based option that would come closest to dairy milk, as pointed out by the Dietary Guidelines for Americans, would be fortified soy beverages, Pikosky says. 

If you're shopping for a nondairy alternative, always check the Nutrition Facts label for those electrolytes to get a better clue into your plant-based milk's hydration benefits.

When Should You Drink Milk Instead of Water for Better Hydration Levels?

It's clear that milk can help hydrate you, but that shouldn't give you the green light to give up on plain water. "Milk is a very healthy addition to a well-balanced diet. But, from a hydration standpoint, shouldn't be your only beverage," Betz says.

The Institute of Medicine suggests that young men (ages 19 to 30) drink around 3.7 liters (125 ounces) and women 2.7 liters (91 ounces) daily. Betz points out that if all of this fluid was 2% milk,  this would add 1,342 to 1,952 calories per day—that could be someone’s entire day’s worth of calories. 

But there are certain scenarios where milk can help hydrate you better than water—like after a seriously sweaty and intensive workout. 

"As a dietitian with a background in exercise physiology, I do recommend people refuel, rehydrate and rebuild after moderate to intense exercise with milk or chocolate milk," Pikosky says. That makes milk a solid sports drink alternative that's more natural, budget-friendly and tastes great, too.  

The Bottom Line

Some studies show that dairy milk may be as hydrating as water—and that's because milk contains a nice natural balance of electrolytes, water and carbs. 

However, "It is important to remember that for most people, water really is the best option for hydration," Betz says.

When you're thirsty, always reach for water first. But if you're feeling extra parched, especially after a sweat-inducing workout, that's a good time to reach for a glass of milk.