Is Anything More Hydrating Than Water? The Surprising Science of Superior Fluid Retention

December 6, 2025 •

5 min read

According to a 2016 study published in the American Journal of Clinical Nutrition, certain beverages were found to be more hydrating than plain water over a short period. The idea that water is the ultimate hydrator is a common belief, but is anything more hydrating than water? The answer involves a fascinating look at how our bodies absorb and retain fluids.

Quick Summary

Certain drinks, such as milk and oral rehydration solutions, can promote superior fluid retention due to their electrolyte and macronutrient content, which helps the body absorb water more effectively and excrete less. These options are particularly beneficial after intense exercise or during illness.

Key Points

Milk's Superiority: Due to its electrolytes, protein, and carbohydrates, milk slows stomach emptying and promotes greater fluid retention than plain water.
ORS for Illness: Oral Rehydration Solutions (ORS) are specifically formulated with a precise balance of sodium, potassium, and glucose to maximize fluid absorption during illness-induced dehydration.
The BHI: The Beverage Hydration Index (BHI), developed in a St. Andrews study, measures a drink's hydration effectiveness compared to still water (1.0). Milk and ORS consistently score higher.
Hydration from Food: A significant portion of daily hydration comes from food. Water-rich fruits and vegetables like cucumber (96% water) and watermelon (92% water) are excellent sources.
Context is Key: While some drinks are more hydrating in specific situations (illness, post-exercise), plain water remains the best and healthiest choice for general, daily fluid intake.
Sports Drinks vs. Water: For most activities, water is fine. During prolonged, intense exercise, sports drinks help replenish electrolytes and carbs more effectively than water alone.
High-Sugar Drinks: Beverages high in concentrated sugars, like sodas and some juices, can actually be less hydrating because they pull water into the intestine to dilute the sugar, reducing overall hydration.

The Science of Hydration: Beyond Water Content

While water is the benchmark for hydration, the effectiveness of a beverage is determined by more than just its water percentage. The presence of electrolytes, carbohydrates, and protein plays a significant role in how well the body retains fluid. This is precisely what a research team at St. Andrews University sought to quantify with their development of the Beverage Hydration Index (BHI).

Understanding the Beverage Hydration Index (BHI)

The BHI measures a drink's ability to maintain fluid balance over a fixed period compared to still water, which is given a score of 1.0. A higher BHI means the body retains more fluid. The study found that several beverages ranked higher than water, including skim milk (1.58), full-fat milk (1.50), and oral rehydration solutions (1.54). The reason? These beverages contain key components that influence absorption and retention.

Why Electrolytes and Macronutrients Matter

When we drink, the water is absorbed through the small intestine. The speed and efficiency of this process are affected by what's dissolved in the fluid. Electrolytes like sodium and potassium, along with carbohydrates and protein, can create an osmotic effect that enhances water absorption and slows the rate at which fluid leaves the stomach. In contrast, plain water on an empty stomach can pass through the system quickly, leading to higher urine output and less overall fluid retention in the short term. Electrolytes, especially sodium, essentially help the body hold onto the water it needs.

More Hydrating Options: A Closer Look

Several drinks offer a hydration boost beyond plain water, making them ideal for specific scenarios like post-workout recovery or combating mild dehydration from illness.

Milk (Skim and Full-Fat): Milk's combination of electrolytes, natural sugars (lactose), protein, and fat slows the digestive process and promotes greater fluid retention. A 2020 study further supported this, noting that milk-based drinks reduced urine loss compared to water or sports drinks.
Oral Rehydration Solutions (ORS): These medical-grade solutions are specifically formulated to replace fluids and electrolytes lost due to diarrhea or vomiting. The balance of glucose, sodium, and potassium facilitates rapid and efficient rehydration, making them more effective than plain water in these acute cases.
Coconut Water: Often dubbed 'nature's sports drink,' coconut water is rich in electrolytes, particularly potassium. This makes it a good option for replenishing minerals lost through sweat, although it contains less sodium than a typical sports drink.
Certain Juices: While many fruit juices are high in sugar and calories, options like orange juice can rank higher on the BHI than water due to their nutrient content. However, high sugar content can also slow absorption, so moderation is key.
Sports Drinks: These are engineered for specific athletic needs, containing electrolytes and carbohydrates to replenish fluids and energy stores. For most everyday activity, water is sufficient, but for prolonged or intense exercise, sports drinks can be more effective for maintaining hydration and performance.

High-Water-Content Foods for Hydration

Around 20% of your daily fluid intake comes from food, with fruits and vegetables being excellent sources. Including these in your diet is a simple and effective way to boost hydration.

Cucumber: With a water content of over 96%, cucumbers are incredibly hydrating.
Watermelon: As its name suggests, watermelon is approximately 92% water and also provides electrolytes.
Celery: This crunchy veggie is about 95% water and contains magnesium and potassium.
Strawberries: Composed of about 91% water, these berries are a delicious way to hydrate.
Lettuce: Iceberg lettuce is 96% water, and other varieties like romaine and spinach also have high water content.
Soups and Broths: These can be over 90% water and are a great source of fluids and electrolytes, especially during illness.

Comparison: Water vs. Other Hydrating Drinks


Feature	Plain Water	Milk (Skim/Full)	Oral Rehydration Solution (ORS)	Sports Drink	High-Water Food (Cucumber)
Best For	Everyday hydration, low-intensity activity, general health.	Post-strenuous exercise, recovery, providing nutrients.	Rehydration during/after illness (diarrhea/vomiting).	Intense or prolonged exercise (over 1 hour).	Daily fluid intake, boosting nutrients.
Key Components	H₂O	H₂O, electrolytes, protein, carbs, fat.	H₂O, electrolytes (Na, K), glucose.	H₂O, electrolytes, carbohydrates.	H₂O, vitamins, minerals, antioxidants.
Fluid Retention	Good, but short-term retention is lower on an empty stomach.	Excellent due to slower digestion and nutrients.	Excellent, scientifically formulated for max absorption.	Good, formulated for rapid absorption.	Gradual absorption over time.
Calorie Count	Zero	Moderate	Low to moderate	Moderate to high (mostly sugar)	Very low
Cost	Low (often free)	Moderate	Moderate	Moderate to high	Moderate
Daily Use	Yes, the gold standard.	As part of a balanced diet; not as sole fluid source.	As-needed for illness or intense dehydration.	Only for specific athletic needs.	Yes, excellent supplement to water intake.

When to Choose What: The Context of Hydration

While the science indicates that other drinks can technically be more hydrating in certain contexts, this does not mean they should replace plain water as your primary source of fluid. For most people, water is the best and cheapest option for daily needs. The key is to match your hydration strategy to your specific needs:

Daily life and moderate activity: Stick with plain water. It has no calories and is perfectly sufficient to keep you hydrated.
After intense, sweaty workouts: Consider a glass of milk or a sports drink to replenish electrolytes and rehydrate more effectively.
During illness with fluid loss (vomiting, diarrhea): Oral rehydration solutions are the most effective and safest choice for quick recovery.
As part of a balanced diet: Incorporate water-rich fruits and vegetables to supplement your fluid intake naturally.

Conclusion: Is Anything More Hydrating Than Water?

The answer is yes, in specific circumstances, something can be more hydrating than plain water. Research has shown that beverages with a combination of electrolytes, carbohydrates, and proteins, like milk and oral rehydration solutions, can lead to superior fluid retention compared to water alone, especially after intense fluid loss. However, these findings do not negate water's status as the fundamental, everyday hydrator. For general health and normal activity, water is king. The real takeaway is that hydration is not one-size-fits-all, and a nuanced understanding of different fluids can help you optimize your hydration strategy when it matters most.

For more information on the Beverage Hydration Index, see this analysis from ACE Fitness: The Hydration Index.

Frequently Asked Questions

Milk contains natural sugars (lactose), proteins, and fats that slow the emptying of fluid from the stomach. This, combined with electrolytes like sodium and potassium, allows the body to absorb and retain the fluid more slowly and effectively than plain water.

Yes. For most people during normal, daily activities, plain water is the best and healthiest way to stay hydrated. It's calorie-free and readily available, and for general purposes, you don't need a more complex solution.

You should use an ORS when you are dehydrated due to illness, such as from vomiting or diarrhea, or after significant fluid loss from heat exhaustion. ORS is formulated to replace lost electrolytes rapidly and efficiently, which plain water cannot do.

Sports drinks can be more hydrating than water, but only during specific circumstances like intense or prolonged exercise (lasting more than an hour) when you need to replace lost carbohydrates and electrolytes. For moderate activity, water is sufficient.

Yes, approximately 20% of your total fluid intake comes from food. Fruits and vegetables like cucumbers, lettuce, watermelon, and spinach have very high water content and contribute significantly to your daily hydration needs.

In very rare cases, yes. Excessive water consumption can lead to hyponatremia, a condition where blood sodium levels become dangerously low. This is most common in endurance athletes who only consume large amounts of plain water over many hours.

Yes, in moderation. While caffeine can have a mild diuretic effect, the total fluid intake from a regular cup of coffee or tea is hydrating. However, relying too heavily on caffeinated drinks is not recommended.