Beyond Water: What is the most hydrating drink ever?

October 14, 2025 •

4 min read

According to research published in the American Journal of Clinical Nutrition, some beverages can hydrate the body more effectively and for a longer duration than plain water, answering the question of what is the most hydrating drink ever under certain circumstances. This surprising finding challenges the common assumption that water is always the superior choice for rehydration, highlighting the critical role of electrolytes, protein, and carbohydrates in fluid retention.

Quick Summary

Studies show that milk and Oral Rehydration Solutions (ORS) retain fluids better than water due to their specific nutrient profiles. These drinks slow gastric emptying, prolonging the hydration effect. While water is optimal for daily fluid intake, specific conditions like intense exercise or illness benefit from beverages with added electrolytes and macronutrients.

Key Points

Milk is surprisingly effective: Research shows milk, particularly skim milk, is more hydrating than plain water due to its electrolytes, protein, and carbohydrates that slow fluid release from the stomach.
ORS is the medical standard: For moderate to severe dehydration caused by illness, Oral Rehydration Solutions (ORS) are superior because they contain a precise balance of electrolytes and glucose for optimal fluid absorption.
Water is the daily champion: For the average person's day-to-day fluid intake, plain water remains the most practical and healthiest choice, being calorie-free and readily available.
Electrolytes are crucial: Minerals like sodium and potassium regulate fluid balance within the body. Their presence in a beverage significantly impacts how long the fluid is retained.
Context is key: The best drink varies based on your level of activity and health. An athlete needs a different rehydration strategy than someone with a stomach bug or a person at rest.
Macronutrients matter: Fat, protein, and carbohydrates in drinks like milk and smoothies contribute to a slower absorption process, leading to a more sustained hydrating effect.
Avoid excessive sugar: While some sugar aids absorption in balanced solutions like ORS, high-sugar beverages like soda and many fruit juices can be counterproductive to hydration.

The Science of Superior Hydration

For decades, water has been seen as the gold standard for hydration. While it is undoubtedly essential for life and perfectly sufficient for most people's daily needs, scientific research reveals a more complex picture. The concept of the Beverage Hydration Index (BHI) was developed to rank drinks based on how much fluid the body retains several hours after consumption. Instead of focusing on quick absorption, the BHI measures longer-term fluid retention, and in this context, certain beverages outperform plain water.

The key to a higher BHI score lies in the beverage's composition of macronutrients (protein, fat, carbohydrates) and electrolytes. These components slow down the rate at which fluid leaves the stomach and is passed out of the body as urine. The presence of sodium also helps the body retain water more effectively. The result is prolonged hydration, which is particularly beneficial after significant fluid loss from sweating or illness.

The Unconventional Champions of Hydration

Milk: An Unexpected Hydration Powerhouse

Surprisingly, milk consistently ranks higher than water on the BHI, with studies showing both skim and full-fat versions lead to better fluid retention. This isn't due to a single component but a synergistic effect of its natural makeup.

Natural Electrolytes: Milk contains essential minerals like sodium, potassium, and calcium that help regulate fluid balance within the body's cells. Sodium, in particular, acts like a magnet for water, encouraging retention and reducing urine output.
Balanced Macronutrients: The combination of natural sugars (lactose), protein, and fat in milk slows gastric emptying. This means the fluid stays in the body longer, providing a sustained hydrating effect. For those with lactose intolerance, some studies suggest lactose-free milk or soy milk can also be effective alternatives.

Oral Rehydration Solutions (ORS): The Medical Standard

For cases of illness involving fluid loss from diarrhea or vomiting, Oral Rehydration Solutions (ORS) are the most effective option. These medically formulated drinks, like Pedialyte, contain specific concentrations of glucose and electrolytes to maximize intestinal fluid absorption. The World Health Organization (WHO) has established specific guidelines for ORS composition, and its use has saved millions of lives by preventing death from diarrheal diseases. Unlike high-sugar beverages that can worsen dehydration, the precise balance in ORS facilitates efficient rehydration.

Hydration for Specific Scenarios

Your ideal hydrating beverage depends on your situation, whether it's everyday life, intense exercise, or recovery from illness.

For daily needs: Plain water is the most practical and healthy choice for the average person. It is calorie-free and widely accessible, making it the perfect staple for daily fluid intake. You don't need the extra calories and electrolytes found in other drinks unless you are engaging in strenuous activity.
For post-exercise recovery: After an intense workout, especially in hot conditions, you lose both water and electrolytes through sweat. This is where milk or a sports drink can be more beneficial than water alone. The carbohydrates and protein aid muscle recovery, while electrolytes replenish lost minerals. Chocolate milk is a popular option for athletes due to its ideal carb-to-protein ratio.
During illness: When dehydration is a concern due to vomiting or diarrhea, an Oral Rehydration Solution is superior. It's specifically designed to restore lost fluids and salts rapidly and safely. Broths and diluted juices are also suitable for mild dehydration.

Comparison of Hydrating Beverages


Beverage	Primary Hydration Mechanism	Key Electrolytes	Added Sugar	Best Use Case
Water	High water content, rapid absorption	Minimal	None	Everyday hydration for most people
Skim Milk	Macronutrients slow gastric emptying	Sodium, Potassium, Calcium	Natural (Lactose)	Post-intense exercise recovery
Oral Rehydration Solution (ORS)	Optimized glucose-sodium co-transport	Sodium, Potassium	Targeted amount	Recovery from moderate illness-related dehydration
Coconut Water	Natural electrolytes	High in Potassium	Varies by brand	Light activity or a less strenuous post-workout option
Sports Drink	Electrolytes and carbs for rapid absorption	Sodium, Potassium	High in many brands	Elite athletes during/after intense exercise
Watermelon Juice	High water content and natural electrolytes	Potassium, Magnesium	Natural (Fructose)	A refreshing, nutrient-dense boost to hydration

Conclusion: The Best Drink Depends on You

Defining what is the most hydrating drink ever depends on the context of your hydration needs. While plain water serves the general public effectively for daily hydration, high-performance athletes or individuals recovering from illness may benefit from drinks that offer more than just H2O. Milk and Oral Rehydration Solutions stand out for their ability to promote longer-lasting fluid retention, thanks to their combination of electrolytes, carbohydrates, protein, and fat. By understanding the science behind different beverages, you can make smarter choices to maintain optimal hydration for any situation. For most, this means a consistent intake of water, supplemented by nutrient-rich options when recovery or specific rehydration is needed. You can read more about the hydration index in the American Journal of Clinical Nutrition.

Frequently Asked Questions

According to studies measuring long-term fluid retention, milk is more hydrating than water because its natural electrolytes, proteins, and fats slow down stomach emptying, allowing the body to absorb and retain fluids for a longer period.

ORS is effective due to its specific formula containing electrolytes like sodium and potassium, and a small amount of glucose. This combination maximizes water and salt absorption in the intestines, making it the most reliable treatment for moderate dehydration from illness.

For most people engaged in regular daily activities, water is sufficient. Sports drinks are primarily useful for elite athletes during or after prolonged, intense exercise, where the electrolytes and carbohydrates help replenish lost minerals and fuel.

Yes, coconut water is a natural source of electrolytes, especially potassium, and is generally lower in sugar than many traditional sports drinks. It is a good option for mild dehydration but lacks the sodium needed to fully replace what's lost during very heavy sweating.

Moderate consumption of caffeinated drinks like coffee and tea is generally as hydrating as water for regular consumers. However, very high doses of caffeine (over 300mg) can have a mild, short-term diuretic effect, especially for those not accustomed to it.

Foods like watermelon, which is 92% water, contribute significantly to your overall fluid intake. They also provide natural electrolytes and nutrients that aid hydration and can be a delicious, nutrient-dense way to rehydrate.

For routine, everyday hydration, plain water is the best choice. It is calorie-free, and the average person does not require the additional electrolytes and macronutrients that make milk or ORS more effective for specific, more intense rehydration scenarios.