Are Isotonic Drinks More Hydrating Than Water?

December 19, 2025 •

4 min read

According to a 2023 study published in the journal Nutrients, while both water and isotonic drinks help maintain fluid balance during exercise, isotonic drinks had a greater impact on hydrating extracellular spaces than plain water. The question of whether are isotonic drinks more hydrating than water, however, depends entirely on the context and duration of your activity.

Quick Summary

The effectiveness of isotonic drinks versus water for hydration depends on exercise intensity and duration. For prolonged, high-intensity activity, isotonic drinks replenish lost electrolytes and carbohydrates more effectively, aiding in fluid retention and performance. For most daily needs and shorter workouts, water is sufficient and avoids excess sugars and calories.

Key Points

Isotonic vs. Water: For the average person and most activities, water is the best and healthiest choice for hydration.
Performance Boost: During intense or prolonged exercise (over 60 minutes), isotonic drinks are more effective due to their ability to replace lost electrolytes and provide energy from carbohydrates.
Electrolyte Balance: Heavy sweating depletes electrolytes like sodium and potassium, which isotonic drinks replenish more effectively than water alone.
Optimal Absorption: Isotonic drinks have an osmolarity similar to body fluids, promoting faster fluid absorption and better fluid retention during strenuous activity.
Hidden Sugars: Many commercial isotonic drinks are high in added sugars and calories, making them a poor choice for casual drinking or short workouts where they are not necessary.
Risk of Imbalance: Over-consuming isotonic drinks when not needed can lead to an electrolyte imbalance and other health issues associated with high sugar intake.
Listen to Your Body: The best hydration strategy involves considering the intensity and duration of your activity and choosing the appropriate fluid to match your body's needs.

The Science of Hydration: Understanding Osmolarity

To understand whether are isotonic drinks more hydrating than water, you must first grasp the concept of osmolarity. Osmolarity refers to the concentration of dissolved particles, such as carbohydrates and electrolytes, in a fluid. This concentration is key to how quickly the body can absorb the liquid.

There are three main categories of drinks based on their osmolarity relative to blood plasma:

Hypotonic drinks: Have a lower concentration of solutes than body fluids. This allows for very rapid absorption, making them ideal for quick fluid replacement without extra energy, such as for short, intense bursts of activity.
Isotonic drinks: Have a similar concentration of salts and sugars to body fluids, typically 6–8% carbohydrates. This similar osmolarity allows for rapid absorption that is more efficient than plain water during high-intensity, prolonged exercise, as it matches the body's natural fluid balance.
Hypertonic drinks: Have a higher concentration of solutes than body fluids. These are designed to provide a large amount of energy and are absorbed slowly. They are best used to replenish glycogen stores after endurance activities and can hinder rehydration if consumed during intense exercise.

When Isotonic Drinks Have the Edge

During prolonged and intense physical activity, especially in hot and humid conditions, the body loses significant amounts of fluid and key electrolytes like sodium and potassium through sweat. In these scenarios, isotonic drinks offer a clear advantage:

Replenishing Electrolytes: An isotonic drink provides a combination of water and electrolytes, which helps restore the balance of salts lost through sweating. This is crucial for proper nerve signaling, muscle function, and preventing cramps. Plain water does not contain sufficient electrolytes to replace what is lost during heavy sweating.
Providing Energy: Isotonic drinks contain carbohydrates (sugars) that serve as a readily available energy source for working muscles. For endurance sports lasting more than an hour, this can help delay the onset of fatigue and improve performance. Water, being calorie-free, does not offer this energy boost.
Enhanced Fluid Absorption: The specific balance of carbohydrates and electrolytes in isotonic drinks stimulates the intestinal absorption of water and sodium. This allows the body to retain fluid more effectively than with plain water, minimizing the risk of dehydration.

When Water Is All You Need

For the average person performing regular, moderate activity, water is not only sufficient but also the healthier choice for hydration.

Daily Hydration: For desk-bound jobs or light, daily activities, water is the best and purest form of hydration. Your normal diet provides enough electrolytes for the body to function efficiently without needing additional sources.
Shorter Workouts: If your exercise session is less than 60 minutes long, you will not lose a significant amount of electrolytes or deplete carbohydrate stores to the extent that a sports drink is necessary. Water is perfectly adequate for keeping you hydrated during and after these workouts.
Controlling Calories and Sugar: Commercial isotonic drinks can be high in added sugars and calories. For someone who is not engaging in prolonged, high-intensity exercise, these extra calories can contribute to weight gain. Drinking water allows you to stay hydrated without the unnecessary caloric intake.

Comparison Table: Isotonic Drinks vs. Water


Feature	Isotonic Drinks	Water
Primary Function	Rapid rehydration, electrolyte replenishment, and energy provision.	Pure hydration and maintenance of bodily functions.
Best For	High-intensity or prolonged exercise (over 60 minutes), especially in hot conditions.	Light to moderate exercise (under 60 minutes), and daily hydration.
Key Ingredients	Water, electrolytes (sodium, potassium), and carbohydrates (sugar).	Pure water, sometimes with trace minerals.
Osmolarity	Similar to body fluids (270-330 mOsm/L), enabling quick absorption.	Very low osmolarity.
Calorie Content	Contains calories from carbohydrates, which can be high.	Zero calories.
Cost	Generally more expensive than water.	Inexpensive and readily available.
Potential Risks	Excess sugar and calories if consumed unnecessarily; dental erosion.	Hyponatremia risk with excessive consumption during extreme endurance events.

Potential Risks of Over-Consumption

While beneficial for athletes, misusing isotonic drinks can lead to health problems. The high sugar content can contribute to weight gain, tooth decay, and potentially increase the risk of metabolic diseases like type 2 diabetes if consumed regularly outside of strenuous activity. Furthermore, consuming too many electrolytes when not needed can lead to an electrolyte imbalance, which can cause symptoms like nausea, weakness, and headaches. For this reason, experts recommend saving isotonic drinks for when they are truly necessary.

Conclusion: Matching Your Drink to Your Activity

In conclusion, the claim that isotonic drinks are inherently more hydrating than water is a nuanced one. For the specific needs of athletes engaged in high-intensity or prolonged exercise, especially in hot climates, the strategic combination of water, electrolytes, and carbohydrates in an isotonic drink makes it superior for rapid fluid and electrolyte replacement, as well as maintaining energy levels. This is crucial for sustaining performance and preventing fatigue.

However, for daily hydration, short workouts, or for those not losing significant amounts of sweat, water remains the best and healthiest choice. The excess sugars and calories in sports drinks are unnecessary for the average person and can contribute to health issues over time. The optimal hydration strategy is not about choosing one drink over the other, but about intelligently matching your fluid intake to your body's specific needs and level of activity. For most people, most of the time, water is the champion of hydration.

For more information on hydration for athletic performance, consult guidelines from organizations like the American College of Sports Medicine (ACSM), which provide evidence-based recommendations for fluid intake during exercise.

Frequently Asked Questions

You should choose an isotonic drink over water for high-intensity or prolonged physical activity lasting more than 60 minutes, or for exercise in hot and humid conditions where you lose a lot of electrolytes through sweat.

No, it is not recommended to drink isotonic drinks every day, especially if you are not engaging in intense exercise. The high sugar and calorie content can contribute to weight gain, and excessive electrolyte intake when not needed can cause an imbalance.

The main difference is the composition and osmolarity. Isotonic drinks contain a balanced mixture of water, electrolytes, and carbohydrates with an osmolarity similar to blood, while water contains none of these added components.

For endurance athletes or those performing intense exercise, yes. Isotonic drinks provide an energy source from carbohydrates and replace vital electrolytes, which can delay fatigue and help sustain performance during long or grueling workouts.

Yes, excessive consumption of commercial isotonic drinks can lead to health risks such as weight gain, dental erosion due to high sugar content, and electrolyte imbalance.

If you are sweating heavily for over an hour during activities like long-distance running, cycling, or high-intensity interval training, an isotonic drink could be beneficial. For lighter, shorter workouts like a gentle walk or a 30-minute gym session, water is sufficient.

Generally, plain water is best for children. Some young athletes in highly demanding sports may need isotonic drinks, but due to the high sugar and sodium content, use should be limited to specific situations and always with parental guidance and careful review of ingredients.