The Surprising Truth: What's More Hydrating Than Water?

October 5, 2025 •

3 min read

According to a 2016 study published in The American Journal of Clinical Nutrition, some common beverages, including milk and oral rehydration solutions, were found to be more hydrating than water over a short period. This surprising finding challenges the long-held assumption that plain H2O is always the most effective fluid for rehydration.

Quick Summary

Scientific research shows that beverages containing electrolytes, protein, and carbohydrates, such as milk and ORS, can be more effective for retaining fluids than water. These nutrients slow fluid absorption, leading to less urine output and longer-lasting hydration.

Key Points

Beverage Hydration Index: A scientific index, not just water content, determines a drink's hydrating potential.
Milk for Rehydration: Due to its electrolytes, protein, and sugars, milk is more hydrating than water over a short period and beneficial post-workout.
Oral Rehydration Solutions: For severe fluid loss from illness, ORS is the most effective fluid for rehydration.
Hydrating Foods: Fruits and vegetables like cucumber, watermelon, and lettuce contain high water content and contribute to daily fluid intake.
Water for Everyday: Despite alternatives, plain water remains the best, healthiest, and most accessible option for general, daily hydration needs.

The Science Behind Superior Hydration

For years, water has been the undisputed champion of hydration. While it remains the gold standard for daily fluid intake, research indicates that for short-term rehydration, especially after intense exercise or illness, other fluids perform even better. The key lies in the fluid's composition and how the body processes it.

Understanding the Beverage Hydration Index (BHI)

The Beverage Hydration Index (BHI) is a tool created by researchers at Scotland's St. Andrews University to rank how well different drinks hydrate the body compared to plain water, which serves as a baseline (with a BHI of 1.0). The index measures fluid retention in the hours following consumption. Drinks with higher scores promote greater fluid retention and, therefore, superior short-term hydration.

The Role of Electrolytes, Proteins, and Carbohydrates

Beverages that outperform water on the BHI typically contain a combination of electrolytes, carbohydrates, and proteins. These components influence the rate of gastric emptying and subsequent water absorption. Electrolytes like sodium and potassium help the body retain fluids rather than immediately passing them out as urine. Protein and carbohydrates slow down the fluid's journey through the stomach and into the small intestine, prolonging the hydration process.

Top Hydrating Drinks Beyond Water

So, what are the drinks that score higher than plain water?

Skim and Full-Fat Milk

Milk is a top contender for short-term hydration, often ranking highest on the BHI, with skim milk performing slightly better than full-fat. Its combination of natural sugars (lactose), protein, fats, and electrolytes like sodium and potassium makes it highly effective for rehydration. This is why many athletes use chocolate milk as a post-workout recovery drink, as it also helps replenish glycogen stores.

Oral Rehydration Solutions (ORS)

Specifically formulated to treat dehydration from illness, ORS is another powerhouse hydrator. These solutions contain a precise ratio of water, electrolytes, and carbohydrates designed for maximum fluid retention. For those suffering from significant fluid loss due to vomiting or diarrhea, ORS is a far more effective treatment than plain water.

Orange Juice

Containing natural sugars, potassium, and vitamin C, orange juice also ranked higher than water in the BHI study. However, it is important to choose 100% orange juice to avoid excessive added sugars, which can have an opposite effect.

Comparison of Hydration Effectiveness

This table summarizes the relative hydrating potential of various common beverages based on the BHI study.


Beverage	Key Hydration Factors	BHI Score (vs. Still Water @ 1.0)
Still Water	Basic fluid replenishment	1.0
Oral Rehydration Solution (ORS)	High electrolytes, moderate sugars	~1.54
Skim Milk	Protein, lactose, high electrolytes	~1.58
Full-Fat Milk	Protein, fat, lactose, high electrolytes	~1.50
Orange Juice	Sugars, potassium, vitamins	~1.39
Sports Drink	Electrolytes, lower sugars than ORS	Not significantly different from water

Hydrating Foods and Context

Beyond beverages, food contributes roughly 20% of your daily water intake. Focusing on water-rich fruits and vegetables is another excellent strategy for boosting hydration.

Highly Hydrating Foods

Cucumbers: 96% water
Iceberg Lettuce: 96% water
Celery: 95% water
Radishes: 95% water
Tomatoes: 94% water
Watermelon: 92% water
Strawberries: 91% water

When to Choose Your Hydration Source

Understanding the context is crucial. While milk or ORS may be more effective for specific rehydration needs, they are not a replacement for daily water intake. Plain water is calorie-free, readily available, and perfect for consistent, everyday hydration without the extra sugars and calories.

Daily Hydration: Stick to plain water. It's the most straightforward way to maintain fluid balance throughout the day for most people.
Post-Intense Exercise: For workouts lasting over an hour or causing heavy sweating, a sports drink, milk, or an ORS can help replenish lost electrolytes and fluids more effectively.
Illness: When experiencing diarrhea or vomiting, oral rehydration solutions are the best choice to replace significant fluid and electrolyte losses.
General Health Boost: Incorporate water-rich fruits and vegetables into your diet to supplement your fluid intake naturally.

The Final Verdict

So, is plain water the best for hydration? The answer depends on the situation. For consistent, everyday fluid intake, it is. However, in specific scenarios requiring more rapid and prolonged fluid retention—like after a strenuous workout or during illness—beverages like milk and oral rehydration solutions can be more hydrating than water due to their nutrient content. The key is to listen to your body and select the right fluid for your specific needs.

Learn more about optimal hydration from authoritative sources like the NIH News in Health.

Frequently Asked Questions

Milk is more hydrating than water over a short period because it contains natural sugars (lactose), protein, and electrolytes like sodium and potassium. These components slow the rate at which fluid leaves the stomach, helping the body retain it longer and reduce urine output.

Coconut water contains electrolytes, but for general hydration, it is not significantly more hydrating than plain water. It can be a good option for a light workout, but plain water is best for regular fluid intake.

You should use an ORS, like Pedialyte, when you have lost significant fluids and electrolytes due to illness, such as vomiting or diarrhea. They are specially formulated for maximum fluid retention and electrolyte replacement.

Not necessarily. The BHI study showed that many standard sports drinks were not significantly more hydrating than water. Their effectiveness depends on the specific electrolyte and carbohydrate concentration, which can vary.

Yes, approximately 20% of your daily fluid intake comes from foods. Water-rich fruits and vegetables like cucumber, watermelon, and celery are excellent choices.

In moderation, coffee can be hydrating, but high caffeine intake (over 300mg or 2-4 cups) can have a mild diuretic effect for some individuals. Adding milk can help offset this effect.

For consistent, day-to-day hydration, plain water is the best choice. It is calorie-free, readily available, and effectively maintains the body's fluid balance without excess sugars or additives.