Is It True That Milk Hydrates You More Than Water? The Surprising Science

October 27, 2025 •

4 min read

According to a 2016 study published in The American Journal of Clinical Nutrition, milk was found to be more hydrating than water in certain situations, a finding that might seem counterintuitive. But is it true that milk hydrates you more than water in all circumstances, or does the nuance lie in the 'how' and 'when'?

Quick Summary

Milk's unique blend of electrolytes, protein, and carbs helps the body retain fluid longer by slowing gastric emptying. This makes it more effective than plain water for rehydration after intense exercise, though water remains the best choice for everyday needs.

Key Points

Milk Offers Superior Fluid Retention: Thanks to its electrolytes, protein, and carbs, milk helps the body retain fluid longer than water.
Ideal for Post-Workout Recovery: Milk is an excellent recovery drink, helping to replenish lost fluids, electrolytes, and muscle glycogen after intense exercise.
Water is Best for Everyday Hydration: For general, low-calorie, daily hydration, plain water is still the most appropriate choice.
Consider Calories and Intolerances: The higher calorie content and potential for lactose intolerance mean milk isn't suitable for everyone or all situations.
Hydration Index Reveals Nuance: Studies show that different beverages have different hydration potentials, with milk and oral rehydration solutions often scoring higher than water.

The Viral Claim: Unpacking the Milk vs. Water Debate

For years, water has been crowned the king of hydration. It's calorie-free, universally available, and essential for life. However, recent studies, particularly from the University of St. Andrews in Scotland, have challenged this notion in certain contexts. These findings revealed that when comparing the hydration effects of various beverages, milk—both skim and whole—actually came out on top of the hydration index. This has led to a flurry of headlines and social media posts, but the full story is more complex than a simple 'milk is better.'

Why Milk Edges Out Water in Fluid Retention

The key to this surprising result lies in milk's nutritional makeup, which plain water lacks. Water is absorbed quickly, which is great for immediate rehydration, but it can also lead to more rapid urination. Milk's combination of nutrients fundamentally changes how the body processes the fluid.

Electrolytes: Milk is a natural source of electrolytes like sodium and potassium. These minerals play a crucial role in regulating fluid balance by helping the body retain water instead of losing it through urination. Sodium, in particular, acts like a sponge, holding fluid in the body for longer.
Protein and Carbohydrates: Milk contains both protein and a natural sugar called lactose. This nutrient profile slows down the rate at which fluid empties from the stomach. A slower gastric emptying time means the body absorbs the fluid over a more extended period, leading to better and more prolonged hydration.
Optimized Osmolality: The balanced concentration of nutrients in milk, known as its osmolarity, also promotes water absorption in the intestines. High sugar drinks like soda can have the opposite effect, potentially pulling water out of the body through osmosis.

When is Milk the Better Choice for Hydration?

For most people in most situations, plain water is perfectly sufficient and the best option. However, for specific scenarios, milk can provide an advantage that water simply cannot match.

Post-Intense Exercise Recovery: After a vigorous workout where significant fluid and electrolyte loss has occurred through sweat, milk is an excellent rehydration drink. The combination of fluid, electrolytes, carbs, and high-quality protein helps replenish lost fluids, restock muscle glycogen stores, and aid in muscle repair. This is why many athletes, especially in endurance sports, turn to chocolate milk as a recovery drink.

Recovery from Mild Dehydration: During periods of mild dehydration caused by factors other than exercise (e.g., illness), milk can provide a gentle, nutritious way to restore fluid and nutrient balance. Its caloric and nutrient density can be particularly beneficial if appetite is low.

Milk vs. Water: A Comparison Table


Feature	Milk	Water	Key Consideration
Best For	Post-exercise recovery, mild dehydration.	Everyday, general hydration.	Match your drink to the situation.
Fluid Retention	High (slower absorption due to nutrients).	Low (very fast absorption).	Milk keeps you hydrated longer.
Nutrient Content	High (electrolytes, protein, carbs, fat).	Low (contains some minerals depending on source).	Milk offers more than just fluid.
Caloric Content	Higher (adds to daily intake).	Zero.	A key factor for weight management.
Cost	Generally more expensive.	Free from the tap.	A budget-friendly option for daily intake.
Gastric Emptying	Slower (slows fluid absorption).	Faster (quick fluid delivery).	Influences how long hydration lasts.

Important Considerations and Limitations

While the science behind milk's hydration potential is sound, it's not a universal recommendation to swap your water bottle for milk. There are several factors to consider.

Calorie Content: The added calories and fat in milk are a significant factor, especially for those on a low-calorie diet. Drinking a large volume of milk daily could lead to unwanted weight gain.
Lactose Intolerance or Allergies: Individuals with lactose intolerance or a dairy allergy cannot reap the benefits of dairy milk and should look for other options, such as oral rehydration solutions. Lactose-free dairy milk is an alternative that retains the electrolytes and protein.
Plant-Based Alternatives: While some plant-based milks, like soy milk, are fortified with electrolytes, they generally do not match the complete nutrient profile of dairy milk that makes it so effective for fluid retention.
Everyday Habits: For the average person, maintaining hydration throughout the day with plain water is the most practical and healthiest approach. The differences in hydration potential from milk are most meaningful after significant fluid loss.

Expert Consensus: When to Choose What

Dietitians and sports nutrition experts agree that both milk and water have their place in a healthy hydration strategy. The choice depends on the specific context and your body's needs. Water should remain your primary beverage for daily hydration, as it delivers fluid without calories and is critical for numerous bodily functions. When you need a more robust rehydration solution that provides electrolytes, carbohydrates, and protein, especially after a tough workout, milk can offer a superior benefit.

Ultimately, the goal is to listen to your body and stay hydrated with a variety of healthy fluids. The hydration debate is less about a single winner and more about understanding the different tools in your hydration toolkit. For general information about fluid balance and the hydration index, authoritative sources like Verywell Health provide excellent context.

Conclusion: The Best Choice Depends on the Context

In conclusion, the claim that milk hydrates you more than water is true under specific conditions, backed by scientific research on the beverage hydration index. The presence of electrolytes, protein, and carbs in milk slows gastric emptying, leading to better fluid retention than plain water. This makes it an especially effective post-exercise recovery drink. However, for everyday hydration needs, water remains the best, lowest-calorie option. Your hydration strategy should be versatile, prioritizing water for general intake while leveraging milk's unique benefits for focused rehydration and recovery. Don't ditch your water bottle, but feel confident grabbing a glass of milk after your next intense workout.

Frequently Asked Questions

No, for general, all-day hydration, water is the best choice. Milk contains calories and nutrients that are not necessary for continuous, low-intensity hydration and could add excessive calories to your diet.

Milk contains electrolytes (like sodium) and macronutrients (protein and carbs). This combination slows the emptying of fluid from the stomach, which allows the body to absorb and retain the liquid over a longer period, resulting in less urine produced.

Milk is often cited as a more effective post-exercise rehydration drink than some commercial sports drinks. It provides a natural blend of protein for muscle repair, carbs for energy replenishment, and electrolytes for fluid balance, making it a budget-friendly and effective option.

Some studies suggest skim milk is slightly more hydrating than whole milk. Both perform better than water in terms of fluid retention, but skim milk's lower fat content may be a minor factor in its absorption and overall effectiveness.

If you are lactose intolerant, you should avoid dairy milk. Alternatives include lactose-free dairy milk or fortified plant-based milks. However, for post-exercise rehydration, a specialized oral rehydration solution (ORS) may be a better alternative.

Generally, no. The majority of plant-based milk alternatives do not have the same natural balance of electrolytes and macronutrients that make dairy milk so effective for fluid retention. Fortified soy milk may come closest, but reading nutrition labels is key.

Contrary to a common myth, moderate consumption of caffeinated beverages like coffee or tea is generally as hydrating as water. High doses of caffeine can have a mild diuretic effect, but this is usually offset by the drink's total fluid volume.