Hydration 101: Practical Tips and the Role of Electrolytes

By Dr. Crionna Tobin, Phd, Optimum Nutrition, Head of Nutrition & Education

Key Learnings

1. What is hydration? Staying hydrated is essential for proper body function. Dehydration can negatively impact performance and overall health.

2. What affects hydration? Heat, diet, and physical activity all influence hydration levels. Drinking fluids consistently and eating hydrating foods help maintain fluid balance.

3. How much water should you drink? Fluid needs vary depending on body size, activity level, environment, and sweat rate. There is no one-size-fits-all recommendation.

4. Hydration and sports performance: Losing just 2% of body weight through dehydration can impair physical performance. Replacing fluids and electrolytes during and after exercise is crucial.

5. What are electrolytes? Electrolytes like sodium, potassium, and magnesium are key for hydration, fluid balance, and muscle function.

6. Do you need electrolytes? Most people can rely on food and water, but prolonged or intense exercise may require electrolyte replenishment to support performance.

What Is Hydration?

Hydration refers to the balance of water in the body, which supports nearly all physiological functions. Your body loses water through breathing, sweating, and urination, so it is important to replace these fluids regularly. Dehydration occurs when fluid loss exceeds intake. Early signs include thirst, but symptoms can progress to fatigue, dizziness, and confusion. Proper hydration is essential for regulating body temperature, maintaining blood pressure, and supporting critical processes like nutrient transport and muscle function.

Signs of dehydration may include: dry mouth or lips, dark yellow urine, fatigue or dizziness, and decreased exercise performance.

Factors That Affect Hydration

Several factors influence how much water your body needs:

• Heat and Weather Conditions: In hot environments, your body sweats more to cool down, increasing fluid loss. Consistent hydration throughout the day, especially during outdoor activities like running or cycling, is essential.

• Diet and Hydrating Foods: Foods high in water content support hydration. Hydrating options include: fruits and vegetables, soups and smoothies and milk.

• Exercise and Sweat Loss: Physical activity increases fluid and electrolyte loss through sweat. Drinking water before, during, and after exercise helps maintain hydration. For workouts longer than one hour, sports drinks with electrolytes may be needed.

How Much Water Should You Drink?

Hydration needs vary based on individual factors such as body size, sweat rate, and activity intensity. As a general guideline, aim for a daily fluid intake of 1.5 to 3 litres of water to maintain proper hydration. During exercise, it is recommended to consume between 500ml and 1 litre of fluids per hour, adjusting for your sweat rate and workout intensity. After exercise, it’s important to replace 1.5 times the fluid lost through sweat — for example, if you lose 1kg during a workout, you should drink 1.5 litres of water to rehydrate effectively.

It’s also important to note that low-water-content foods like bread, starchy carbohydrates, cakes, biscuits, and cheese contribute less to your overall fluid intake, making direct water consumption even more critical for maintaining hydration levels.

Hydration and Sports Performance

Proper hydration is critical for athletes. Losing just 2% of body weight through sweat can reduce endurance, strength, and cognitive performance. For example, an athlete weighing 85kg should aim to limit fluid loss to less than 1.7kg during exercise1,2. Sweating is the body’s main cooling mechanism. Sweat contains water and electrolytes, primarily sodium, which need to be replaced to prevent dehydration and maintain performance.

What are electrolytes?

Electrolytes are minerals that regulate fluid balance, muscle contractions, and nerve function. The main electrolytes lost in sweat include sodium, potassium, magnesium, and calcium. Sodium helps retain water and maintain blood pressure. Potassium supports muscle function and fluid balance. Magnesium aids muscle relaxation and energy production. Calcium is important for muscle contraction and nerve signaling.

Sodium is especially important because it helps with water absorption and prevents hyponatremia (low sodium levels), which can occur if water intake is high but sodium is not replenished.

Do You Need to Take Electrolytes?

Electrolyte needs depend on exercise duration, intensity, and individual sweat rate. Sodium loss through sweat can range from 460 to 1840 mg per litre3. Follow these practical guidelines to stay properly hydrated.

• Low-intensity exercise (under 1 hour): Water is typically sufficient.

• Exercise longer than 60 minutes or in hot conditions: Use sports drinks with electrolytes or eat salty snacks like pretzels or crackers alongside fluids.

• Estimate sweat loss: Weigh yourself before and after exercise. For each kilogram lost, drink about 1.5 litres of fluid to rehydrate.

References

1. Sawka, M.N., and T.D. Noakes (2007). Does dehydration impair exercise performance? Med. Sci. Sports Exerc. 39:1209-1217.

2. Cheuvront SN, Kenefick RW. Dehydration: physiology, assessment, and performance effects. Compr Physiol. 2014 Jan;4(1):257-85. doi: 10.1002/cphy.c130017. PMID: 24692140.

3. Baker, L. B., Ungaro, C. T., Barnes, K. A., Nuccio, R. P., & Reimel, A. J. (2016). Validity of regional sweat rate predictions in athletes. Medicine & Science in Sports & Exercise, 48(9), 1934-1946.