Does Milk Hydrate You? The Surprising Truth

December 19, 2025 •

3 min read

According to a study from Scotland's St. Andrews University, milk was found to be more hydrating than plain water due to its unique nutritional profile. So, does milk hydrate you effectively? The answer is a surprising 'yes,' especially in certain situations like after exercise or during mild dehydration.

Quick Summary

Milk's combination of electrolytes, natural sugars, protein, and fat slows its emptying from the stomach, allowing the body to retain fluids longer. This makes milk a powerful hydration beverage, particularly beneficial for post-exercise recovery or replenishing lost fluids.

Key Points

Sustained Hydration: Milk is proven to hydrate the body more effectively over a longer duration than plain water because its nutrients slow down gastric emptying.
Electrolyte Content: The natural sodium and potassium in milk are crucial for fluid balance, helping the body to retain water more efficiently than water alone.
Post-Exercise Recovery: Milk, especially chocolate milk, is an excellent recovery beverage after strenuous workouts, replenishing fluids, electrolytes, and providing protein for muscle repair.
High in Nutrients: Beyond hydration, milk offers protein, carbohydrates, and essential vitamins, making it a comprehensive and cost-effective recovery drink.
Not for Everyday Replacement: For routine, everyday hydration, plain water is still the best and lowest-calorie option. Milk's higher calorie and fat content should be considered.
Fat Content Affects Water %: Skim milk has a slightly higher water content than whole milk, making it technically more hydrating on a pure volume basis, though both are superior to water for sustained hydration.

The Science Behind Milk's Hydration Power

For decades, water has been seen as the gold standard for hydration. While it remains a critical component of daily fluid intake, emerging research suggests milk might be a superior option for retaining fluids over a longer period. This is not a matter of pure water content, but rather the synergistic effect of milk's complex nutrient composition.

How Milk's Nutrients Affect Hydration

Milk contains a natural blend of components that work together to optimize fluid balance in the body:

Electrolytes: Minerals like sodium and potassium, naturally present in milk, play a crucial role in fluid regulation. Sodium, in particular, helps the body hold onto water, reducing urine output and promoting rehydration. Potassium is also essential for maintaining fluid balance, particularly inside cells.
Proteins: Milk contains high-quality proteins, such as whey and casein, which slow down the digestion process. This delayed gastric emptying means fluids are absorbed more gradually over a longer period, leading to sustained hydration.
Carbohydrates: The natural sugar in milk, lactose, also contributes to slower digestion. In appropriate amounts, carbohydrates facilitate the absorption of water and electrolytes from the small intestine into the bloodstream.
Fats: Similar to protein, the fat content, especially in whole milk, helps slow digestion and fluid release from the stomach, further prolonging the body's hydration.

This rich nutritional matrix is why studies using the Beverage Hydration Index (BHI) have shown milk to be more effective than water at maintaining hydration status over a few hours. Water provides quick hydration, but a significant portion is lost relatively quickly through urination.

Milk vs. Water vs. Sports Drinks

When considering rehydration, particularly after exercise, milk offers a comprehensive package that often outperforms plain water and traditional sports drinks. Water replenishes fluids but lacks the electrolytes and macronutrients needed for more complete recovery. Sports drinks provide carbohydrates and electrolytes but lack the high-quality protein found in milk, which is vital for muscle repair. The natural combination of electrolytes, carbohydrates, and proteins in milk makes it a multi-purpose recovery beverage.

Should You Drink Milk for Hydration?

For general, daily hydration needs, water remains the most practical and healthiest choice. It's calorie-free and widely accessible. However, milk offers significant benefits in specific contexts:

After intense exercise: Post-workout, milk can be an excellent choice to replenish fluids, electrolytes, and glycogen stores while also providing protein for muscle repair. Chocolate milk is especially popular with athletes for its optimal carbohydrate-to-protein ratio.
During mild illness: When experiencing mild dehydration from illness, the electrolytes and nutrients in milk can aid in rehydration.
In specific populations: For children and the elderly, who may be more susceptible to dehydration, milk can promote more effective hydration due to the enhanced fluid retention.

However, it is important to consider individual dietary needs and health conditions. Those with lactose intolerance, milk allergies, or a vegan lifestyle should opt for water or other non-dairy hydrating options. Furthermore, the calorie content of milk means it may not be suitable as a primary hydration source for those managing their weight.

Comparison of Hydrating Beverages


Beverage	Water Content	Electrolytes	Protein	Carbohydrates	Calorie Content	Rehydration Speed	Sustained Hydration	Best Use Case
Water	High (~100%)	None	None	None	0	Fast	Low	Everyday, general hydration
Skim Milk	High (~91%)	High	High	Moderate	Moderate	Moderate	High	Post-exercise recovery, sustained hydration
Whole Milk	Moderate (~88%)	High	High	Moderate	High	Slow	High	Post-exercise recovery, increased nutrient needs
Sports Drink	High	High	None	High	Moderate	Fast	Moderate	Intense, long-duration exercise
Oral Rehydration Solution	High	Very High	None	Moderate	Low	Fast	High	Treating illness-related dehydration

Conclusion: The Final Verdict on Milk's Hydration

While water is and should remain the go-to for daily fluid intake, the question, 'Does milk hydrate you?' has a scientifically nuanced and positive answer. Due to its balanced composition of electrolytes, protein, and carbohydrates, milk is highly effective at promoting fluid retention, especially when compared to plain water over several hours. For specific scenarios like post-workout recovery or combating mild dehydration, milk provides a potent, nutrient-dense solution. However, individuals should weigh the caloric intake and consider any dietary restrictions. In the larger context of a healthy diet, incorporating milk can offer both hydration and nutritional benefits, but it is not a replacement for regular, mindful water consumption. Ultimately, the choice depends on your specific hydration goals and overall health profile.

Disclaimer: This article is for informational purposes only. Consult a healthcare professional or registered dietitian for personalized dietary advice.

Frequently Asked Questions

For sustained hydration over several hours, studies indicate that milk is better than plain water. The combination of milk's natural sugars, electrolytes, protein, and fat slows down fluid release from the stomach, helping the body retain fluid for longer.

Milk is hydrating due to its nutrient composition. It contains electrolytes like sodium and potassium, along with protein and carbohydrates. These components aid in better water absorption and retention, prolonging the body's hydration compared to water alone.

Yes, chocolate milk is often considered an ideal post-workout recovery drink. Its balance of carbohydrates, protein, and electrolytes is excellent for replenishing energy stores, repairing muscles, and restoring fluid balance.

Technically, skim milk has a slightly higher percentage of water than whole milk due to its lower fat content. While both are effective for hydration, some studies suggest skim milk might be marginally more hydrating for this reason, though both are better than water for prolonged fluid retention.

Water is the best choice for those with lactose intolerance or a milk allergy, vegans, and people who are managing their weight or calorie intake. For general daily fluid needs, plain water remains the healthiest option.

For mild dehydration, especially after exercise, milk can be a suitable option due to its electrolytes. However, for severe dehydration caused by significant fluid loss (e.g., from diarrhea), a medical-grade oral rehydration solution is specifically formulated for optimal electrolyte and fluid replacement.

Plant-based milks can be hydrating, but their electrolyte and nutrient profiles vary widely. They typically contain fewer electrolytes than cow's milk and may have added sugars. Cow's milk is generally superior for nutrient-rich rehydration unless you have a specific dietary restriction.