Does Drinking Milk Help with Hydration? The Surprising Scientific Evidence

October 19, 2025 •

4 min read

According to studies utilizing the Beverage Hydration Index, milk—both skim and whole—has been shown to hydrate the body more effectively and for a longer duration than plain water. This surprising fact reveals a nuanced answer to the question: Does drinking milk help with hydration?

Quick Summary

Milk's hydrating properties are attributed to its electrolytes, protein, and carbohydrates, which slow stomach emptying and improve fluid retention. While water is ideal for general hydration, milk offers superior rehydration benefits after intense exercise due to its comprehensive nutritional content.

Key Points

Superior Fluid Retention: Milk contains electrolytes, protein, and carbohydrates that slow gastric emptying, leading to better and more sustained fluid retention compared to plain water.
Ideal for Post-Exercise Recovery: Milk is an excellent post-workout beverage, providing not only fluid and electrolytes but also protein and carbs for muscle repair and energy replenishment.
Water is Best for Everyday: Despite milk's advantages in certain scenarios, plain water remains the optimal choice for general, day-to-day hydration needs due to its lack of calories.
Fat Content's Minor Role: Both skim and whole milk are effective hydrating agents, though skim milk has a slightly higher water percentage. The primary hydrating effect comes from other components.
Effective for Mild Dehydration: In cases of mild dehydration, such as after an illness, milk's ability to retain fluids for longer makes it a beneficial option.
Rich in Electrolytes: Milk is a natural source of key electrolytes like sodium, potassium, and calcium, which are crucial for maintaining the body's fluid balance.

The Scientific Edge: Why Milk Outperforms Water in Some Cases

For years, water has been the undisputed champion of hydration. However, recent scientific studies have introduced a compelling challenger: milk. The reason milk can be more hydrating than plain water for sustained periods lies in its unique nutritional makeup. Plain water is absorbed quickly by the body, which is excellent for rapid rehydration, but it can also lead to faster urine production. Milk, on the other hand, contains a blend of components that work together to promote better fluid retention.

The Trifecta of Hydration: Electrolytes, Protein, and Carbohydrates

Milk's effectiveness comes down to three key components:

Electrolytes: Milk is a natural source of essential electrolytes, including sodium, potassium, and calcium. These minerals are vital for regulating fluid balance in the body. When you sweat, you lose these electrolytes, and milk helps replenish them effectively, which in turn helps your body retain fluids more efficiently.
Protein and Carbohydrates: The protein and carbohydrates found in milk, including natural lactose, play a crucial role in the hydration process. This combination slows the emptying of fluids from the stomach, which allows the body to absorb and utilize the liquid over a longer period. For athletes, this is especially beneficial as the carbohydrates also help replenish energy stores.
Isotonic Balance: The balance of water, carbohydrates, and electrolytes in milk gives it an osmolarity similar to the body's own fluids. This balanced concentration promotes more efficient absorption and distribution of water, further enhancing its hydrating effect.

Milk vs. Other Beverages for Hydration

To understand milk's place in your hydration strategy, it's helpful to compare it directly to other common drinks. The Beverage Hydration Index (BHI) provides a useful framework, measuring a drink's hydration effectiveness relative to still water.


Feature	Milk (Skim/Whole)	Plain Water	Sports Drink	Orange Juice
BHI Score	High (higher than water)	Baseline (1.0)	Varies (similar to water)	High (higher than water)
Retention Period	Longer (slower gastric emptying)	Shorter (rapid absorption)	Moderate (varies by formulation)	Longer (slower digestion)
Key Components	Water, Protein, Carbs, Electrolytes	Water	Water, Carbs, Added Electrolytes	Water, Natural Sugars, Vitamins, Some Electrolytes
Best Use Case	Post-exercise recovery, sustained hydration	General daily hydration	During prolonged intense exercise	As part of a balanced diet, not primary rehydration
Calorie Count	Higher	None	Varies (often high sugar)	Higher

The Role of Fat Content and Context

While milk's hydration power comes from a combination of nutrients, its fat content does have a slight influence. Skim milk contains a higher percentage of water than whole milk, making it technically the most hydrating option among dairy milks, according to the USDA. However, studies show that both skim and whole milk are more effective than water at promoting sustained fluid retention. The higher fat and protein content in whole milk can slow digestion even further, but the key hydrating mechanisms are present in all dairy milk variations.

When is Milk the Optimal Choice for Hydration?

For general, day-to-day fluid intake, water remains the best choice due to its lack of calories and added sugars. However, milk shines in specific scenarios:

After Intense Exercise: Replenishes fluids, electrolytes, and offers a balanced ratio of carbohydrates and protein for muscle recovery.
When Recovering from Mild Dehydration: The sustained fluid retention can be particularly useful during periods of mild dehydration, such as following an illness.
For Children and the Elderly: The complete nutritional profile can promote more complete hydration, especially for populations that may struggle with consistent fluid intake.
As a Recovery Drink Alternative: Milk provides a more natural, budget-friendly alternative to commercial sports drinks for post-workout needs.

Conclusion

In conclusion, the answer to "Does drinking milk help with hydration?" is a definitive yes, with some important nuances. For daily, routine fluid intake, water is the ideal choice. However, in situations requiring more robust rehydration, such as after intense exercise or in cases of mild dehydration, milk proves to be a powerful and effective alternative. Its natural combination of electrolytes, protein, and carbohydrates helps the body retain fluids for longer, outperforming plain water in key scenarios. By understanding the science, you can make smarter hydration choices to support your body's specific needs.

FluidLogic has more information on hydration for intense conditions.

When is milk a good hydration choice? A quick list:

After a strenuous gym session to replenish electrolytes and kickstart muscle recovery.
For children who need both hydration and essential nutrients for growth.
As a bedtime beverage to aid in prolonged hydration overnight.
When sick with mild dehydration from illness, to aid fluid retention.
As a nutritious alternative to sugary sports drinks.

Frequently Asked Questions

For sustained hydration, particularly after exercise, studies show milk can be more effective than water due to its nutritional content. However, water is the best option for everyday, general hydration without extra calories.

Milk contains electrolytes (sodium, potassium), proteins, and natural sugars (lactose). These components slow the digestive process, causing fluids to be released and absorbed by the body over a longer period, resulting in greater fluid retention.

Yes, chocolate milk is often considered an excellent post-workout recovery drink. It provides a great balance of carbohydrates, protein, and electrolytes to help replenish energy stores and aid muscle repair.

Skim milk is technically the most hydrating due to its higher water content compared to higher-fat milks. However, both skim and whole milk offer superior prolonged hydration benefits over water.

No, drinking milk does not cause dehydration. While beverages high in concentrated sugars can lead to fluid being pulled into the intestines (osmosis), the sugar in milk is balanced by other nutrients, making it a hydrating choice.

The electrolytes in milk, such as sodium and potassium, help regulate the body's fluid balance. Sodium, in particular, helps the body retain water, preventing excessive urine production and promoting overall fluid retention.

The best time to choose milk is after an intensive workout or any strenuous physical activity. This is when your body needs not only fluid replacement but also electrolytes and macronutrients for recovery.