What liquid hydrates you more than water?

October 10, 2025 •

5 min read

According to a 2016 study from Scotland's St. Andrews University, not all beverages hydrate the body equally. The study found that certain liquids, like milk and oral rehydration solutions, can provide more lasting hydration than plain water due to their nutrient composition, which helps the body retain fluid more effectively. So, if you've ever wondered what liquid hydrates you more than water, the answer lies in understanding the complex interplay between a beverage's contents and your body's physiological processes.

Quick Summary

Several beverages, including milk and oral rehydration solutions, can offer more effective hydration than plain water, especially for lasting fluid retention. This is due to their composition, which includes electrolytes, protein, and fat. These components slow stomach emptying and improve fluid absorption, as measured by the Beverage Hydration Index.

Key Points

Milk is highly hydrating: Studies show that milk, both full-fat and skim, is more hydrating than water due to its protein, fat, carbohydrates (lactose), and electrolyte content.
Oral Rehydration Solutions are most effective for illness: Scientifically formulated ORS are highly efficient at replacing lost fluids and electrolytes, especially during illness with significant fluid loss from vomiting or diarrhea.
Nutrient content is key for lasting hydration: Drinks with a balanced mix of electrolytes, sugars, and protein slow gastric emptying, allowing for more gradual absorption and better fluid retention compared to plain water.
The Beverage Hydration Index (BHI) quantifies effectiveness: The BHI measures a drink's ability to keep you hydrated over time. Liquids with a higher BHI score, like milk and ORS, perform better than water.
Water is still the best for general daily needs: While some liquids offer superior hydration in specific scenarios, plain water is the most practical, healthy, and cost-effective choice for most people's everyday fluid requirements.
High-sugar drinks can be less effective: Beverages with very high sugar concentrations, such as sugary sodas and some juices, can actually be less hydrating because the body pulls water into the intestine to dilute them.
Foods contribute to hydration: Many fruits and vegetables, such as watermelon, cucumber, and lettuce, have high water content and contribute significantly to your overall daily hydration.

Understanding the Beverage Hydration Index (BHI)

To understand why some drinks are more hydrating than water, we must first look at the concept of the Beverage Hydration Index (BHI). Developed by researchers, the BHI measures how well a drink helps the body retain fluid over a period of time, using still water as a baseline with a score of 1.0. Beverages with a BHI higher than 1.0 are more hydrating than water, while those with a lower score are less effective.

The key factors influencing a drink's BHI score are its electrolyte content, carbohydrates, and protein. A balanced combination of these nutrients slows down the process of gastric emptying, meaning the liquid stays in the stomach longer and is absorbed more slowly into the bloodstream. This prevents a sudden, large increase in fluid volume that the kidneys must quickly filter, leading to less urine production and better overall fluid retention.

Milk: The Hydration Powerhouse

Among the liquids studied, both full-fat and skim milk consistently ranked higher than water on the BHI. The reason for milk's superior hydrating ability is a synergistic combination of its natural components:

Electrolytes: Milk is rich in electrolytes like sodium and potassium. Sodium, in particular, acts as a sponge, helping the body hold onto water. Potassium is another vital electrolyte for maintaining fluid balance.
Carbohydrates: The natural sugar, lactose, helps in the transport and absorption of water in the intestines.
Protein and Fat: The presence of protein and fat further slows down gastric emptying. This allows for a more gradual, sustained absorption of fluids, preventing the kidneys from flushing it out too quickly.

This makes milk an excellent post-exercise recovery drink, helping to replenish not just lost fluids but also electrolytes and providing a small amount of fuel.

Oral Rehydration Solutions (ORS)

Specifically formulated to treat and prevent dehydration, oral rehydration solutions are a top-tier option for fluid replacement, especially during illness causing vomiting or diarrhea. Their effectiveness comes from a precise balance of ingredients:

Glucose: Small amounts of sugar aid in the transport of sodium and water across the intestinal wall, ensuring rapid and efficient fluid uptake.
Electrolytes: ORS contains sodium and potassium at scientifically determined levels to replace what the body has lost.
Osmolarity: The specific concentration of sugars and salts is designed to facilitate faster absorption than plain water, quickly restoring fluid balance.

While ORS is not a daily drink for the average healthy person, it is the most effective liquid for rehydrating during significant fluid loss.

Other Hydrating Beverages

While milk and ORS lead the pack, other beverages also offer solid hydrating properties:

Fruit and Vegetable Juices (in moderation): 100% fruit juice, with its high water and vitamin content, can be hydrating. However, the high sugar content can slow absorption and may not be the best choice for everyday hydration. Diluting juice with water is a good strategy to reduce sugar intake.
Coconut Water: This natural beverage is a good source of potassium and carbohydrates, making it a decent option for rehydrating after light to moderate activity.
Smoothies: Blending water-rich fruits and vegetables creates a hydrating drink that also provides fiber and nutrients. Adding a protein source can further enhance its rehydration potential.

Comparing Hydration Efficiency: The BHI at a Glance


Beverage	BHI Score (relative to still water)	Key Reasons for Score
Still Water	1.0	Standard baseline for hydration effectiveness.
Skim Milk	~1.58	Electrolytes (sodium, potassium), protein, and lactose slow absorption.
Full-Fat Milk	~1.50	Similar to skim milk, with added fat further slowing gastric emptying.
Oral Rehydration Solution	~1.54	Optimized balance of sodium, glucose, and potassium for rapid absorption during dehydration.
Orange Juice	~1.39 (unadjusted)	High water content and electrolytes, but also high sugar, which can pull water from the body in concentrated form.
Sports Drinks	~1.2	Formulated with electrolytes and carbohydrates for rapid absorption during intense exercise.
Coffee (moderate)	~0.9	High water content largely counteracts the mild diuretic effect of caffeine.
Beer	~0.9	Alcohol's diuretic effect slightly outweighs its water content.
Soda (regular)	~1.0	High sugar can inhibit absorption, making it no better than water despite its water content.

BHI scores are approximate and can vary slightly based on different study parameters.

The Role of Foods in Hydration

Staying hydrated isn't just about what you drink; many foods also contribute significantly to your fluid intake. Water-rich fruits and vegetables can be a delicious way to supplement your daily fluid needs.

Some top hydrating foods include:

Watermelon (92% water)
Strawberries (91% water)
Cucumber (95% water)
Lettuce (96% water)
Tomatoes (95% water)

Incorporating these foods into your diet helps you consume fluids alongside essential vitamins, minerals, and fiber, promoting holistic hydration.

Water Remains the King for Daily Hydration

While other liquids may outperform water in specific scenarios (like intense exercise or illness-induced dehydration), plain water remains the gold standard for daily, general hydration. It is calorie-free, inexpensive, and readily available, making it the most sensible choice for most people.

Practical Hydration Tips:

Monitor your urine: Pale, straw-colored urine is a good indicator of adequate hydration.
Listen to your body: While thirst is a signal that you're already slightly dehydrated, it's a good reminder to drink.
Hydrate throughout the day: Don't wait until you're thirsty to start drinking. Sip fluids consistently.
Flavor your water: If you find plain water boring, add slices of lemon, lime, or cucumber to make it more appealing.

Ultimately, understanding the BHI and the science behind hydration helps you make informed choices. For specialized hydration needs, drinks with electrolytes, fat, and protein might be superior, but for everyday wellness, simple water is unbeatable.

Conclusion: Tailoring Your Hydration

The notion that no liquid is more hydrating than water is a myth. For specific situations, such as post-exercise recovery or rehydration from illness, liquids with a richer nutrient profile, like milk or oral rehydration solutions, can actually be more effective due to their ability to be absorbed and retained by the body over a longer period. However, for most people engaging in normal daily activities, water is more than sufficient and remains the healthiest, most practical choice for consistent hydration. The key is to match your fluid intake to your body's specific needs, whether that means reaching for a glass of milk after a tough workout or sipping plain water throughout the day. For more authoritative guidance on hydration and nutrition, you can consult resources like the CDC's page on healthy drinks: https://www.cdc.gov/healthy-weight-growth/water-healthy-drinks/index.html.

Frequently Asked Questions

Milk is more hydrating than water because it contains electrolytes like sodium and potassium, along with protein and carbohydrates. These components slow down the rate at which fluid leaves the stomach, allowing for a more gradual and sustained absorption into the bloodstream and less urine production.

Yes, ORS are designed to be more hydrating than plain water for specific situations like dehydration from illness. Their scientifically formulated blend of sugar and electrolytes ensures rapid and efficient fluid absorption in the intestines.

Yes, when consumed in moderation, coffee and tea can be hydrating. While caffeine is a mild diuretic, the high water content of these beverages largely offsets this effect for regular drinkers. For example, a moderate amount of coffee has a hydration effect similar to water.

Sports drinks are formulated to rehydrate athletes after intense or prolonged exercise by replenishing both fluid and electrolytes lost through sweat. However, for everyday hydration, especially without strenuous activity, plain water is generally sufficient and a healthier choice due to the added sugars in many sports drinks.

The BHI is a scientific ranking of how effectively different beverages hydrate the body over time. Water is used as the baseline with a score of 1.0, and beverages like milk and ORS have higher scores because their nutrient composition helps the body retain fluid more effectively.

The best approach is a combination of both. Drinking water is the most direct way to hydrate, but eating water-rich fruits and vegetables like watermelon and cucumber contributes significantly to your overall fluid intake while also providing essential nutrients and fiber.

Yes, milk can be a good hydrating beverage for anyone. Its balance of electrolytes, fat, and protein provides effective hydration, even for daily needs. Low-fat or skim options are available for those mindful of calorie intake.