What is the number one most hydrating drink?

October 3, 2025 •

4 min read

While most people reach for water to quench their thirst, a study from Scotland's St. Andrews University found that plain water is not the most hydrating beverage available. The surprising reality is that the most hydrating drinks are those containing a little extra help, in the form of electrolytes and nutrients, to aid the body's fluid retention. So, what is the number one most hydrating drink, and when should you choose it?

Quick Summary

Examines a study revealing that certain beverages like milk and oral rehydration solutions are more hydrating than water due to their nutrient content. This overview ranks the most effective hydrating drinks, explaining the science behind each one's benefits for different situations, such as post-exercise or during illness.

Key Points

Milk is surprisingly more hydrating than water: A study showed milk's content of fat, protein, and electrolytes helps the body retain fluid longer, outperforming plain water in the Beverage Hydration Index.
Oral Rehydration Solutions (ORS) are the most effective for illness: Scientifically formulated with a precise balance of water, glucose, and salts, ORS is the gold standard for treating moderate to severe dehydration from diarrhea or vomiting.
Water remains the best choice for daily, calorie-free hydration: For general day-to-day fluid intake, water is the most accessible, zero-calorie, and essential beverage.
Electrolytes are key to fluid retention: Drinks containing minerals like sodium and potassium aid the body's ability to hold onto water, rather than passing it quickly through urination.
Other hydrating options include coconut water and broths: Coconut water is a natural source of electrolytes, while nutrient-rich broths can also effectively replenish lost fluids and minerals.
Sports drinks can be high in sugar and are best for intense exercise: While designed to replenish electrolytes and carbs for athletes, many sports drinks contain high amounts of added sugar and artificial ingredients, making them less ideal for general hydration.
Listen to your body's thirst cues and urine color: Pay attention to thirst and the color of your urine (it should be pale yellow) to gauge your hydration level.

The Science of Optimal Hydration

When it comes to staying properly hydrated, it's not just about how much liquid you consume but also how well your body retains it. Plain water, while essential and calorie-free, passes through the body relatively quickly. Other beverages, however, contain components that slow down the process of gastric emptying, allowing for more sustained fluid retention. A scientific study published in The American Journal of Clinical Nutrition developed a "Beverage Hydration Index" (BHI) to rank how well 13 different drinks maintained hydration. This research revealed some unexpected results that challenge the conventional wisdom that plain water is always the superior choice for hydration.

Why Nutrients are Key for Hydration

The secret to a drink’s hydrating power lies in its composition. Beverages with small amounts of electrolytes (such as sodium and potassium), carbohydrates (sugars), and protein facilitate greater fluid retention in the body.

Electrolytes: Minerals like sodium help the body hold onto water, reducing urine output. After intense exercise or illness, replenishing these lost electrolytes is crucial for effective rehydration.
Carbohydrates and Protein: The presence of these macronutrients slows down the rate at which fluid empties from the stomach. This slower absorption allows the body to utilize the fluid over a longer period, making it more hydrating than plain water over time.

Milk: The Unexpected Champion

According to the St. Andrews study, both fat-free and whole milk scored higher on the BHI than water, placing milk among the most hydrating beverages tested. This is due to its optimal blend of water, natural sugars (lactose), high-quality protein, and electrolytes like sodium and potassium. For athletes, especially after a tough workout, milk helps with both rehydration and muscle recovery, making it a very effective post-exercise drink.

The Gold Standard for Rehydration: Oral Rehydration Solutions (ORS)

While milk is surprisingly effective, the undisputed leader for treating moderate to severe dehydration—especially due to illness—is an Oral Rehydration Solution (ORS). These are scientifically formulated to contain the precise ratio of water, glucose, sodium, and potassium to maximize fluid absorption in the intestines. ORS works by leveraging a specific transport mechanism in the gut that pairs sodium and glucose absorption, which in turn pulls water into the body's circulation far more efficiently than water alone. The World Health Organization (WHO) and UNICEF have championed ORS for decades for its life-saving ability to combat dehydration from diarrheal diseases. While not a typical daily drink, its formulation makes it the gold standard for rapid and therapeutic rehydration.

Comparison of Top Hydrating Drinks


Drink	Everyday Hydration	Post-Workout	Illness/Moderate Dehydration	Key Nutrients	Considerations
Oral Rehydration Solution (ORS)	No (unless indicated)	Optional	Excellent	Glucose, Sodium, Potassium	Therapeutic, specifically formulated; not for casual use.
Milk (Skim/Low-Fat)	Good	Excellent	Good	Protein, Lactose, Calcium, Sodium, Potassium	More calorie-dense than water; best for sustained hydration.
Water	Excellent	Good	Fair	None (except minerals in some tap/bottled)	The most accessible and fundamental option for daily intake.
Coconut Water	Good	Good	Fair	Potassium, Magnesium, Sodium	Lower in sodium than milk/ORS; check for added sugars.
Fruit Juice (100%)	Fair	Fair	Fair	Vitamins, Natural Sugars, Potassium	High sugar content can be less hydrating than milk.
Sports Drink	Fair	Good	Fair	Electrolytes, Carbohydrates	Often high in added sugar and artificial ingredients.

Best Practices for Choosing Your Hydration

Your ideal hydrating drink depends on the situation. For daily consumption, water is still the best and most fundamental choice, as it is calorie-free and readily available. For post-workout recovery or when a more sustained hydration effect is needed, milk offers a great balance of fluid, electrolytes, and nutrients for muscle repair. In cases of illness with significant fluid loss, a properly prepared oral rehydration solution is the most effective and safest option.

Making Informed Choices

Beyond the top contenders, many other beverages and foods contribute to hydration. Natural sources like watermelon, cucumber, and leafy greens have high water content. Similarly, soups and broths provide both fluids and sodium, making them effective for rehydration, particularly when sick. By understanding the role of different nutrients in fluid retention, you can make informed decisions based on your body's specific needs.

Homemade Hydration Alternatives

For those seeking a low-cost, readily available alternative, simple recipes can be just as effective. A DIY oral rehydration solution can be made with a mixture of clean water, sugar, and salt, though commercially available packets are recommended for precise formulation. For everyday flavored hydration, adding fruits or herbs like lemon, cucumber, or mint to water can make drinking more enjoyable.

Conclusion: The Final Verdict on Hydration

While water is the indispensable foundation of a healthy hydration strategy, the title for the single most hydrating drink goes to oral rehydration solutions due to their scientifically-engineered ability to maximize fluid and electrolyte absorption. For more general, everyday purposes, or for post-exercise recovery, milk is an excellent contender thanks to its superior fluid retention capabilities compared to water. By understanding the strengths of these different beverages, you can choose the right option to meet your body's hydration needs, ensuring optimal health and performance. Ultimately, the best hydration strategy involves consuming a variety of healthy fluids and listening to your body's thirst signals throughout the day.

Frequently Asked Questions

For immediate fluid replacement, water is effective, but for long-term fluid retention, studies show it is not the most hydrating. Beverages containing electrolytes, protein, and carbohydrates, like milk or oral rehydration solutions, are better at helping the body hold onto fluid for longer periods.

Milk is more hydrating than water because it contains a mix of protein, natural sugars, and electrolytes. This combination slows down the emptying of fluid from the stomach, which allows the body to retain fluids over a longer duration and reduce urine output.

An ORS is a therapeutic beverage made of water, glucose, and specific electrolytes (sodium and potassium) in a precise ratio. It is used to treat moderate to severe dehydration, especially resulting from diarrhea or vomiting, by maximizing fluid absorption in the intestines.

For most people's daily activities, water is sufficient. Sports drinks are formulated for endurance athletes to replace fluids, electrolytes, and carbohydrates lost during intense or prolonged exercise, but they often contain high levels of added sugar.

Coconut water is a good source of electrolytes, particularly potassium, and is lower in calories than many sports drinks. However, it is not as high in sodium as milk or ORS, so it may not be as effective for replacing sweat loss.

You should use an ORS when experiencing moderate dehydration, especially due to illness with significant fluid loss from vomiting or diarrhea. It is not necessary for general daily hydration, for which water is best.

A simple way to check your hydration level is to observe the color of your urine. Pale yellow urine indicates proper hydration, while dark yellow urine suggests you need to drink more fluids. Thirst is also a key indicator, but waiting until you are thirsty means you are already mildly dehydrated.