Is it good to drink milk when dehydrated? A scientific look

December 23, 2025 •

3 min read

According to research from Scotland's St. Andrews University, milk can be more effective for hydration than plain water, especially for sustained fluid retention. While water is often considered the gold standard, the nutritional composition of milk offers unique advantages, leading many to ask, "is it good to drink milk when dehydrated?"

Quick Summary

Milk can be an effective rehydration fluid due to its water, electrolytes, protein, and natural sugars, which help the body retain fluids longer than water alone. However, its high caloric content means it should not completely replace water for everyday hydration. It is particularly useful for mild dehydration, such as after exercise, but water remains the best option for severe cases.

Key Points

Superior Fluid Retention: Milk is more hydrating than plain water due to its nutritional content, which helps the body retain fluids longer and reduces urine output.
Nutrient-Rich Profile: The combination of water, electrolytes (sodium, potassium), carbohydrates (lactose), and protein makes milk a powerful rehydration fluid, especially after exercise.
Excellent for Post-Exercise Recovery: Milk, particularly chocolate milk, is an ideal recovery drink that helps replenish energy stores and repair muscles due to its balanced macronutrient and electrolyte content.
Mild Dehydration Only: While effective for mild dehydration, milk should not be the sole source of hydration for general fluid intake due to its calorie density. For severe dehydration, water is the quickest solution.
Lactose Intolerance Considerations: Those who are lactose intolerant should be cautious, as consuming milk could cause digestive distress and worsen dehydration.
Skim vs. Whole Milk: Both skim and whole milk are effective for rehydration, but skim milk is slightly more hydrating and lower in calories, making it a potentially better choice for less intense scenarios.

The Science Behind Milk and Hydration

Unlike plain water, milk is a complex fluid containing a blend of water, electrolytes (like sodium and potassium), carbohydrates (lactose), and proteins. This unique composition is the key to its superior fluid retention capabilities. The sodium in milk acts like a sponge, helping the body hold onto water and reducing the amount of fluid lost through urination. The proteins and fats in milk slow down gastric emptying, leading to a more gradual absorption of fluids over a longer period.

How Milk Compares to Other Drinks

Several studies have directly compared the hydrating effects of milk to other common beverages. A 2016 study, for instance, measured fluid retention in participants who drank various fluids. It found that milk (both whole and skim) and an oral rehydration solution were the most effective at maintaining hydration, outperforming water and sports drinks. This is because sports drinks, while containing electrolytes, often have a more concentrated sugar content that can cause the body to pull water from its own tissues to dilute the fluid, counteracting the rehydration process. Milk's balance of nutrients avoids this effect.

Milk for Exercise Recovery

Milk, especially chocolate milk, has long been recommended as a recovery drink for athletes. Its balanced ratio of carbohydrates, protein, and electrolytes helps replenish glycogen stores, repair muscles, and restore fluid balance more effectively than many commercial sports drinks. The protein in milk, which includes casein and whey, provides a sustained release of amino acids for muscle repair and building. For individuals engaged in intense or prolonged exercise, drinking milk is a cost-effective and nutritious way to recover.

Potential Downsides and Considerations

Despite its hydrating benefits, milk is not without its drawbacks. Its higher caloric content compared to water can be a concern for those managing their weight. For daily, casual hydration, relying solely on milk could lead to an excessive calorie intake. Furthermore, individuals with lactose intolerance may experience digestive issues like bloating, gas, and diarrhea, which would exacerbate dehydration symptoms rather than resolve them. In these cases, lactose-free milk or a different rehydration strategy is necessary.

Different Types of Milk and Their Hydration Effect

Not all milk is created equal when it comes to hydration. Research indicates that skim milk can be slightly more hydrating than whole milk, potentially due to its lower fat content. However, both types are still highly effective. For everyday, light activity, skim milk might be the better choice to limit calories, while post-workout scenarios could benefit from the more energy-dense whole milk, or a carbohydrate-rich option like chocolate milk.

The Role of Milk Alternatives

With the rise of vegan diets, plant-based milk alternatives are popular. However, the hydration properties of these drinks vary widely. Many plant-based options have less sodium and potassium than dairy milk, and may contain added sugars. For those avoiding dairy, it's crucial to check the nutritional label for electrolyte content or choose fortified varieties. Soy milk is often cited as the alternative with a nutritional profile closest to dairy milk.

Comparison Table: Milk vs. Other Fluids


Feature	Dairy Milk (Skim)	Water	Sports Drink	Orange Juice
Hydration Index	High (Often higher than water)	Baseline (1.0)	Moderate to High	High
Electrolyte Content	High (Na, K, Ca)	Low to None	High (Na, K)	High (K)
Natural Sugars	Yes (Lactose)	No	Added Sugars	High (Fructose)
Protein Content	High	None	None	Low
Caloric Density	Moderate	Zero	Moderate	Moderate to High
Best For	Exercise recovery, mild dehydration	Everyday hydration	Intense, prolonged exercise	Quick energy boost

Conclusion

Drinking milk when mildly dehydrated can be a highly effective strategy for restoring fluid balance. Its unique combination of water, electrolytes, protein, and natural sugars helps the body retain fluids longer than water alone, making it a powerful rehydration tool, especially after exercise. However, it should be seen as a complement to water, not a replacement, particularly for general daily hydration due to its caloric density. Individuals with lactose intolerance should seek alternatives. For severe dehydration, medical attention is paramount, as water is the fastest route for fluid absorption. For most people in mild states of dehydration, a glass of milk can be a beneficial and nutritious choice.

Reference: A comprehensive review of beverages and their hydration properties can be found in the American Journal of Clinical Nutrition.

Frequently Asked Questions

Yes, several studies have shown that milk can be more hydrating than plain water because its natural electrolytes, proteins, and fats help the body retain fluids more effectively over a longer period.

Milk is particularly beneficial for rehydration after a period of mild fluid loss, such as following a sweaty workout. It is not recommended as the sole beverage for everyday hydration due to its calories.

If you have lactose intolerance, consuming milk can cause bloating, gas, and diarrhea, which would be counterproductive when trying to rehydrate. In this case, lactose-free milk or an alternative beverage is a better option.

Research suggests that skim milk is slightly more hydrating than whole milk and is lower in calories, making it a good choice for general rehydration. Whole milk offers more calories, which can be beneficial for athletes needing extra energy.

Yes, chocolate milk is often recommended for athletes as a recovery drink because it provides an ideal mix of carbohydrates, protein, and electrolytes to help replenish energy stores and repair muscles after exercise.

The Beverage Hydration Index (BHI) is a measure of how well a drink hydrates the body compared to plain water. Studies have found that milk has a higher BHI than water, indicating it is more effective at promoting fluid retention.

No, while milk can be a very effective rehydration fluid, especially in specific scenarios like post-exercise, water should remain your primary beverage for overall daily hydration. Water is calorie-free and quickly absorbed, making it suitable for all situations.