You often hear a general recommendation to drink 2 L of water a day. It sounds simple. But does it apply to everyone? What if you exercise, it is hot or you barely sweat? Is hydration in sport different from hydration for someone who is inactive?
And does that amount include water from solid foods? Or liquids such as milk?
There are plenty of questions. Let’s work through them.
What is hydration, and why does it matter?
Hydration means supplying the body’s tissues with the water they need.
To put this in context, the body’s chemical reactions rely on an aqueous environment. Disturbances in fluid balance can affect muscles, concentration and organs such as the liver and kidneys. Maintaining appropriate hydration matters, especially during exercise.
Why is adequate hydration essential for sport?
- Dehydration and a related rise in body temperature can both affect sports performance.
- Even excellent sleep, coaching, nutrition and blood-test results cannot compensate for severe dehydration. Too little fluid can force you to stop, and the warning signs can be unpleasant.
- After substantial sweat loss, rehydration may require more than plain water: electrolytes from food or drinks can help replace losses.
- By extra electrolytes, we do not mean beer. It is not a good recovery drink.
- Drinking excessive amounts can also be harmful. Plan fluid intake around thirst, conditions and individual losses rather than forcing litres at once; overdrinking can cause dangerous dilution of blood sodium.
Hydration should be personalised to the exercise and athlete, helping maintain fluid and electrolyte balance. A loss of around 2% or more of body mass during exercise can affect performance in some settings, although this is not a universal diagnostic threshold.
Effects of dehydration
Symptoms can become more pronounced as dehydration worsens. They may include:
- Greater exercise-related stress.
- Increased body temperature
- Increased heart rate and perceived effort
- Reduced physical performance
- Cramps or severe headaches, though these can also have other causes.
Inadequate hydration can reduce plasma volume and blood flow to the digestive tract. This is one possible contributor to digestive discomfort during intense exercise.
How much water should I drink?
Sweat rate, body size, exercise, humidity and temperature all influence fluid needs.
Your sweat rate is the amount of sweat lost during 1 hour of training. Heat generally increases sweating as your body dissipates exercise-generated heat, increasing fluid and electrolyte losses. Adapt your hydration plan accordingly.
As you can imagine, 2 L of water per day may not be right for you. The amount and composition need to reflect the athlete, including sweat rate, and the particular training session. Both the sports diet and hydration plan change with these demands.
Hydration guidelines for sport
Where appropriate, sports drinks can supply 6–9% carbohydrate, mainly readily available sugars, and sodium at around 0.5–0.7 g per litre. The original article also describes total sodium intakes of 0.5–1.2 g per hour using drinks, salty foods or salt tablets. These are context-dependent ranges, not automatic requirements; sodium does not make excessive drinking safe.
A commonly cited pre-exercise guide is 5–7 ml per kilogram over the 3–4 hours before training, adjusted to individual needs.
For effective post-workout recovery, one guide is approximately 1.5 L of fluid per kilogram lost, spread over recovery. The original article suggests drinks containing 0.3–0.7 g of sodium per litre, plus carbohydrate, with protein considered where useful. Individualise the plan rather than forcing intake.
As always, adapt these guidelines to each athlete. Like nutrition, hydration should be personalised with support from sports nutritionists.
Which foods contain the most water?
Remember: we eat water as well as drink it. The original article estimates that around 30% of intake comes from food, though this varies. Foods contribute to overall hydration.
For example, hake is about 76% water and yoghurt about 86%. Lettuce, oranges, tomatoes and cucumbers are also water-rich. A boiled egg provides protein as well as water.
If you find drinking water difficult, dishes such as gazpacho, salmorejo, vegetable soups and salads can contribute to your nutritional plan.
Fancy something sweet? Homemade ice creams can also contribute fluid as part of your diet.
Remember that a hydration plan that suits you may differ from the one that suits your coach, trail-running partner or CrossFit partner.
Your eating and hydration plan is as unique as you are. A nutritionist can help you understand why, and teach you to manage the many variables involved in truly personalised nutrition.
