Is Water Just as Good as Milk for Hydration and Health?

November 11, 2025 •

4 min read

According to a 2016 study in the American Journal of Clinical Nutrition, milk may actually be more effective than water at maintaining hydration for a longer period of time, especially after exercise. This surprising finding raises the question: Is water just as good as milk for total hydration and overall health, or does one have an advantage in certain situations? We dive into the nutritional composition and health implications of both beverages.

Quick Summary

This article compares water and milk for hydration and nutritional benefits. It details how milk's electrolytes and macronutrients can enhance fluid retention, particularly after exercise, while highlighting water's role as the optimal zero-calorie choice for general, daily hydration. The discussion also covers nutrient differences, including calcium for bone health, and considers dietary factors like calories and intolerances.

Key Points

Hydration Duration: Milk may hydrate for a longer period than water, primarily due to its fat, protein, and electrolyte content, which slows gastric emptying.
Nutrient Density: Water is calorie-free but lacks macronutrients, whereas milk is nutrient-dense, providing protein, calcium, vitamins, and minerals.
Post-Exercise Recovery: Milk, especially low-fat, can be a highly effective post-exercise recovery drink, helping to replenish lost fluids and electrolytes, and support muscle repair.
Everyday Hydration: For general, day-to-day hydration without extra calories or fat, water is the gold standard and best choice.
Bone Health: While milk is an excellent source of calcium, other foods and fortified beverages also provide this mineral, challenging the idea that milk is the only path to strong bones.
Plant-Based Alternatives: Fortified soy milk is nutritionally comparable to dairy milk in some respects, but consumers should check labels on all plant-based milks for added sugars and fortification levels.
Dietary Considerations: The right choice depends on individual dietary needs; those with lactose intolerance, milk allergies, or specific caloric goals should consider alternatives.

Water vs. Milk: The Fundamental Differences

When comparing water and milk, it’s essential to first understand their fundamental differences. Water is a simple compound, consisting only of hydrogen and oxygen, that provides pure, calorie-free hydration. It is the most essential nutrient for the human body, playing a crucial role in temperature regulation, joint lubrication, organ protection, and waste removal. In contrast, milk is a complex beverage that contains water, but also delivers a host of macronutrients and micronutrients, including proteins, carbohydrates (lactose), fats, and electrolytes such as calcium, sodium, and potassium.

The Science of Hydration: Why Milk Can Retain Fluid Longer

While water is absorbed quickly by the body, research from the University of St. Andrews suggests that milk's nutritional makeup allows for longer-lasting hydration. The fats, proteins, and carbohydrates in milk slow down the rate at which fluid is emptied from the stomach, which can lead to better overall fluid retention. This is particularly beneficial for athletes recovering from intense, sweaty workouts, where replenishing electrolytes and fluid balance is critical. Plain water, while effective for immediate thirst, lacks these additional components that aid in prolonged fluid retention. For regular, low-intensity activity, however, water remains the ideal choice due to its lack of calories and added sugars.

Nutritional Comparison Beyond Hydration

The most significant distinction between water and milk lies in their nutritional content. Water provides zero calories and no macronutrients, while milk is a nutrient-dense food source. This difference is key when considering overall dietary needs.

Nutrients in Milk

Calcium: An excellent source for bone and dental health.
Protein: Contains high-quality protein (casein and whey), essential for muscle repair and growth.
Vitamins: Often fortified with Vitamins A and D, and naturally contains B vitamins like B12.
Minerals: Provides potassium, magnesium, and phosphorus.

Nutrients in Water

Minerals: Can contain trace minerals depending on the source (e.g., mineral water), but levels vary.

This nutritional contrast means that milk contributes significantly to daily nutrient intake, but also adds calories and fat, which may not be suitable for everyone or for all hydration needs.

Milk Alternatives: A Consideration for Those with Intolerances or Dietary Restrictions

For individuals with lactose intolerance, dairy allergies, or those following a vegan diet, cow's milk is not an option. Fortunately, a wide variety of plant-based milk alternatives exist, though their nutritional profiles differ. Fortified soy milk is one of the few plant-based options that closely matches cow's milk in protein and calcium content. Other alternatives, like almond and oat milk, are often lower in calories and protein but are also fortified to offer a source of calcium and Vitamin D. Consumers should carefully check nutrition labels, as some plant-based options are higher in added sugars.

Water vs. Milk: A Comparative Table


Feature	Water	Cow's Milk (Low-Fat)	Plant-Based Milk (Fortified Soy)
Primary Function	Calorie-free hydration, waste removal, joint lubrication.	Hydration plus a source of complete nutrition.	Hydration with varying nutrient profiles; alternative for dairy-free diets.
Hydration Efficiency	Excellent for general hydration; absorbs quickly.	Potentially more effective for prolonged hydration due to electrolytes and macronutrients, especially post-exercise.	Contributes to hydration, but fluid retention may not be as prolonged as cow's milk.
Calories	0	Approx. 102 calories per 8 oz.	Varies, e.g., Unsweetened Soy: ~80 calories per 8 oz.
Protein	0g	8g per 8 oz.	Varies, e.g., Soy: ~7-8g per 8 oz.
Calcium	Trace amounts, if any.	Excellent source, approx. 305mg per 8 oz.	Excellent source when fortified, approx. 300mg per 8 oz.
Electrolytes	Trace amounts of minerals.	Excellent source of sodium, potassium, calcium.	Varies greatly; typically added via fortification.
Best For...	Daily, consistent fluid intake; low-calorie hydration.	Post-exercise recovery; nutrient-dense beverage.	Dairy-free diets; those seeking specific plant-based nutrients.

Making the Right Choice for Your Health

Choosing between water and milk ultimately depends on individual health goals, dietary needs, and physical activity levels. While milk can be a highly nutritious beverage that aids in prolonged rehydration and provides essential vitamins, minerals, and protein, it also comes with a caloric load. For the average person seeking simple, calorie-free hydration throughout the day, water is the best and most fundamental option. Those engaging in strenuous exercise or needing extra nutrients may find milk an excellent post-workout recovery tool. The dairy industry is not the only source of important nutrients, and other foods rich in calcium and vitamins exist.

In conclusion, rather than viewing them as competing entities, water and milk can be seen as complementary. Water is the foundation of healthy hydration, while milk can be a valuable, nutrient-rich supplement for specific nutritional goals. Consulting with a healthcare professional or registered dietitian can help you determine the right balance for your unique lifestyle and needs. For further information on managing your fluid intake, see the guidelines from the CDC on healthier drinks (https://www.cdc.gov/healthy-weight-growth/water-healthy-drinks/index.html).

Frequently Asked Questions

For immediate hydration, water is the most efficient choice. However, for prolonged hydration, especially after strenuous exercise, milk can be more effective because its electrolytes, protein, and carbohydrates help the body retain fluids for a longer period.

Yes, milk is significantly more nutrient-dense than water. A single cup of milk provides a rich source of high-quality protein, calcium, phosphorus, potassium, and vitamins A, B12, and D (if fortified), all of which are not present in plain water.

While water can replace the fluid component of milk, it cannot replace its nutrients. If removing milk from a diet, it is important to find alternative sources for key nutrients like calcium, protein, and Vitamin D through other foods or fortified plant-based milk alternatives.

Milk is a practical way to meet calcium requirements for bone health, but it is not necessary. A variety of foods, including dark leafy greens, fortified juices, and certain mineral waters, also provide calcium. Exercise and other nutrients like vitamin D also play crucial roles.

Milk can be a particularly good choice over water for post-exercise recovery, as it helps replenish lost fluids, electrolytes, carbohydrates, and protein, aiding in muscle repair and rehydration.

Nutritional content varies widely among plant-based milk alternatives. Fortified soy milk is often the closest nutritionally to cow's milk, but others like almond or oat milk may be lower in protein and require fortification to match vitamin and mineral levels.

Excessive milk consumption can lead to issues due to high caloric intake and potential digestive problems, especially for those with lactose intolerance. For many, moderation is key, and water should be the primary source of daily fluid.