What to drink on hot days – is plain water enough?

High ambient temperatures affect many processes in the human body, one of the most important being thermoregulation. On hot days, the body reacts with intense sweating to maintain the right internal temperature. This defence mechanism protects against overheating, but it comes at a price – along with sweat, we lose water and essential minerals. Dehydration progresses faster in summer than in cooler months and can affect anyone, regardless of age or level of physical activity.

1. Is clean water enough?
2. Electrolytes – what do we lose with sweat?
3. For whom are electrolyte drinks a better choice?
4. How to choose drinks with electrolytes in summer?
5. Summary – smart hydration on hot days

Even a slight decrease in hydration can cause headaches, drowsiness, concentration problems and poor well-being, while more serious deficiencies can lead to dangerous heat stroke. Therefore, proper hydration in summer is not only a matter of comfort, but of real health and safety.

Is clean water enough?

Although clean water is the basis of healthy hydration, it is not always the optimal choice in hot weather. Water effectively quenches thirst and does not provide unnecessary calories, but its disadvantage in extreme conditions may be the lack of electrolytes, which are necessary to maintain fluid balance in the body. During intense sweating, the body does not only lose water – it also loses sodium, potassium, magnesium and chlorine.

Drinking large amounts of water alone can paradoxically exacerbate the problem, as it dilutes the concentration of electrolytes in the plasma. This can lead to hyponatraemia, or low sodium levels in the blood. Therefore, especially in conditions of high exertion or high temperatures, it is worth considering more complex hydration than just pure water.

Electrolytes – what do we lose with sweat?

Electrolytes are electrically charged minerals that perform key functions in the body – they regulate water and electrolyte balance, nerve conduction, muscle contractions and pH balance. The most important ones are sodium, potassium, calcium, magnesium and chlorides. Their concentration must be constantly maintained at the right level, and any significant loss – e.g. through sweat – should be compensated for. On hot days, the body loses up to several litres of sweat a day, and with it, significant amounts of electrolytes.

A deficiency can result in muscle cramps, fatigue, a drop in blood pressure and even heart rhythm disturbances. Replenishing electrolytes is therefore not only recommended for athletes, but also for people who are active in the summer, travelling, doing physical work or spending many hours in the sun.

For whom are electrolyte drinks a better choice?

Although water is usually sufficient for the average person relaxing in the shade or working in an air-conditioned office, there are groups that need more. Electrolyte drinks are recommended, among others, for people who engage in intense physical activity, spend long periods of time in the sun, children and seniors, as well as people with a tendency to low blood pressure. In these cases, plain water may not provide full regeneration of the water and mineral balance.

People travelling in tropical climates or training outdoors in full sun should also reach for drinks with added electrolytes. It is also worth remembering that children dehydrate more quickly, and seniors often have a reduced sense of thirst, which can make the effects of fluid deficiency more severe. In such situations, electrolytes can help restore the body's balance and avoid the negative effects of heat.

How to choose drinks with electrolytes in summer?

Not all isotonic or electrolyte drinks work the same way. When choosing the right product for summer, it is worth paying attention to the sodium content – this is the element lost in the largest amounts during sweating. Good electrolyte drinks should also provide potassium, magnesium and possibly calcium. The sugar content is also important – in sports drinks, it can be higher to aid fluid absorption and replenish energy, but for less active people, low-sugar or completely sugar-free products are a better choice.

From a practical point of view, electrolytes in powder form or effervescent tablets, which can be prepared independently in a bottle of water, are also an advantage. It is worth avoiding flavoured drinks containing artificial colours and preservatives, which do not have a beneficial effect on the body in conditions of high thermal stress.

Summary – smart hydration on hot days

On hot days, the body's needs change significantly, and proper hydration is one of the key elements of health. Although clean water is irreplaceable in everyday life, in conditions of high temperature and increased sweating, it may not be enough to maintain full electrolyte balance. In such situations, it is worth reaching for drinks with electrolytes, which replenish not only water but also valuable elements.

This does not mean that everyone has to give up water in favour of isotonic drinks, but in many cases – especially among physically active people, children and seniors – mineral-enriched drinks are a better choice. Smart hydration is not about the amount of fluids you drink, but their quality and adaptation to the real needs of your body.

Sources:

• Fluid and electrolyte supplementation for exercise heat stress https://www.sciencedirect.com/science/article/pii/S0002916523067370
• Water, hydration, and health https://pubmed.ncbi.nlm.nih.gov/20646222/
• Water and electrolyte needs for football training and match-play https://pubmed.ncbi.nlm.nih.gov/16766499/