What is more hydrating than water? The surprising science of fluid absorption

December 31, 2025 •

3 min read

According to a study from Scotland's St. Andrews University, milk, oral rehydration solutions, and even orange juice can be more hydrating than plain water over a four-hour period. This unexpected finding challenges the common assumption that water is the absolute best hydrator, leading many to question what is more hydrating than water and why.

Quick Summary

Certain beverages with electrolytes, protein, and moderate sugar can promote more sustained hydration than plain water. These added nutrients slow fluid emptying from the stomach and increase water retention, making them more effective in specific situations like illness or intense exercise.

Key Points

Superior Hydrators: Drinks like milk and oral rehydration solutions (ORS) are more hydrating than plain water due to their nutrient composition.
Electrolytes Matter: Sodium and potassium in beverages help the body retain fluid more effectively than water alone, which is vital after sweating heavily.
Slow Absorption is Key: The natural sugars, fats, and proteins in some drinks, like milk, slow down gastric emptying, leading to longer-lasting hydration.
Context is Critical: Plain water is excellent for general, everyday hydration, while alternatives like ORS or milk are more effective for specific situations like illness or post-exercise recovery.
Hydrating Foods: Many fruits and vegetables with high water content, such as cucumbers and watermelon, also contribute significantly to your daily fluid intake.
Homemade Options: You can make your own cost-effective hydrating drink by adding a pinch of salt and a small amount of honey or juice to water.

The Science Behind Superior Hydration

While plain water effectively hydrates the body quickly, it can also pass through the digestive system and kidneys quite rapidly, especially when consumed in large volumes on an empty stomach. The key to achieving superior, longer-lasting hydration lies in a beverage's composition, specifically its content of electrolytes, sugars, and fats. These elements influence the body's fluid retention in a few key ways:

Electrolytes: Minerals like sodium and potassium act as a "sponge," helping the body hold onto water and maintain its fluid balance. This is crucial after heavy sweating or illness, when these minerals are lost.
Sugar and Fat: A small amount of sugar, and fat, can slow down the rate at which fluid empties from the stomach. This slower absorption allows the body to retain more fluid over a longer period.

Top Hydrating Alternatives to Water

Based on the science, here are some of the most effective alternatives for sustained hydration:

Oral Rehydration Solutions (ORS)

Engineered for medical use, ORS is arguably the most effective option for rehydration after significant fluid loss from diarrhea or intense exercise.

Key Ingredients: ORS contains precise amounts of electrolytes (sodium and potassium) and glucose. The glucose and sodium work together to enhance water absorption in the small intestine, accelerating rehydration.

Milk (Skim and Whole)

Researchers have repeatedly found that milk is more hydrating than water.

Why it works: Milk contains lactose (a natural sugar), protein, and fat. This combination slows gastric emptying, allowing for more gradual and prolonged fluid absorption. Milk's sodium content also aids in fluid retention.

Fruit and Vegetable Juices

Benefits: Juices like orange juice contain natural sugars and electrolytes that can enhance fluid absorption.
Considerations: Moderation is key. Juices contain more concentrated sugars and calories than whole fruits. High-sugar beverages can actually pull water from the body in the small intestine to dilute the sugar, making them less effective for hydration than their lower-sugar counterparts.

Homemade Electrolyte Drink

For a natural, low-sugar alternative, you can create your own effective hydrating beverage:

Combine 1 liter of water with a pinch of salt (for sodium) and a small amount of honey or lemon juice (for glucose and flavor).

Hydrating Foods: A Surprising Source of Fluid

Foods with high water content can contribute significantly to your daily fluid intake. This is an excellent, low-calorie way to stay hydrated.

Water-rich produce includes:
- Cucumbers (95% water)
- Lettuce (96% water)
- Celery (95% water)
- Watermelon (92% water)
- Strawberries (91% water)
Other options: Soup broths are also an excellent source of fluid and electrolytes.

Water vs. Alternatives: Which Should You Choose?

The choice between plain water and a more complex hydrating beverage depends entirely on the situation. While alternatives can provide a more sustained boost in specific scenarios, water remains the gold standard for daily, routine hydration.

Hydration Comparison: Water vs. Alternatives


Feature	Plain Water	Milk	Oral Rehydration Solution (ORS)
Hydration Speed	Very fast	Slower (sustained)	Fast
Hydration Duration	Short-term	Prolonged	Prolonged
Key Nutrients	Pure H2O	Lactose, Protein, Fat, Sodium	Glucose, Sodium, Potassium
Use Case	Everyday, general hydration	Post-exercise recovery, everyday use	Illness (vomiting, diarrhea), intense exercise
Calories	Zero	Moderate	Moderate
Best For	Regular daily fluid needs	Intense physical activity and recovery	Rapid rehydration from significant fluid loss

Conclusion: Tailor Your Hydration Strategy

In conclusion, the question of what is more hydrating than water has a nuanced answer. While plain water is essential for life and perfectly adequate for daily needs, beverages containing electrolytes, proteins, and carbohydrates can be more effective for prolonged hydration, especially after significant fluid loss. For most people, most of the time, plain water is the best and healthiest choice. However, athletes, individuals recovering from illness, or those in hot environments may benefit from incorporating drinks like milk or oral rehydration solutions to maintain optimal fluid balance. Ultimately, the best hydration strategy is one that is tailored to your individual needs and circumstances. For more information on the study, you can refer to the research findings discussed by Harvard Health.

Make Hydration a Habit

For everyday purposes, the most effective way to stay hydrated is to make it a consistent habit. Here are a few simple tips:

Carry a reusable water bottle with you and sip throughout the day.
Infuse plain water with fruits or herbs like lemon, cucumber, or mint to enhance the flavor.
Drink water before and after meals and exercise to supplement your intake.
Remember that many foods, especially fruits and vegetables, contribute to your fluid needs.

Frequently Asked Questions

Yes, studies have shown that milk is more hydrating than plain water. Its natural lactose, protein, and fat slow down fluid absorption, allowing the body to retain moisture for a longer period.

An ORS is a solution containing water, glucose, and electrolytes (sodium and potassium) designed to rehydrate the body faster and more effectively than plain water. It is best used for rapid rehydration after significant fluid loss from illness, like diarrhea or vomiting, or from intense, prolonged exercise.

For most people engaged in general activity, plain water is sufficient. Sports drinks are primarily useful for athletes undertaking intense exercise lasting more than an hour, as they replace electrolytes and provide carbohydrates for energy.

Moderate consumption of caffeinated drinks like coffee and tea is generally hydrating, as the fluid intake outweighs any mild diuretic effect. However, water is still the best calorie-free option for consistent daily hydration.

Drinks with very high sugar content, like soda and concentrated juices, are less hydrating because they cause a physiological process called osmosis, which pulls water from the body into the small intestine to dilute the sugar. This can actually work against proper hydration.

Many fruits and vegetables are excellent sources of hydration due to their high water content. Examples include watermelon, cucumbers, strawberries, celery, and lettuce.

For daily hydration during regular activities and light exercise, plain water is the best choice. It is calorie-free, easily accessible, and perfectly effective for replenishing lost fluids.