How much water you should drink?

This is a real burning question, especially when we are going through a heatwave! I have seen all sorts of advice on social media – drink four litres of water per day, start your day with a pint of lukewarm water, drink only distilled water, etc...

As a general guideline, you should drink 30 to 35ml of water per kilogram of your body weight. To give you an example, this translates to 2.1 litres (approximately eight glasses) for someone weighing around 60kg. It is true that hot climates, exercising or sweating excessively require an increased water intake.

What are the signs of dehydration?

Signs of dehydration can range from subtle to severe, depending on the degree of fluid loss. The most common signs are a dry mouth, feeling thirsty, dark yellow urine, fatigue, headache, dry skin, brain fog and muscle cramps. It is essential to rehydrate quickly by drinking small sips of room-temperature water. Cool water can lead to a temperature shock and make things even worse; the same applies to drinking large amounts of water in one go.

Is it possible to drink too much water?

It is very possible. Many people, prompted by social media or unqualified healthcare professionals, think that the more you drink, the better it is. However, not everyone needs to drink four litres of water, plus herbal teas, every day. I see this advice being given often by personal trainers, saying that because you are exercising you need to increase fluids, but there is a big difference in loss of fluids if you are training at moderate intensity for 45 minutes in a gym with air con or if you are playing professional sports in the open air on a warm day.

Drinking excessive amounts of water, especially without replacing electrolytes, can lead to electrolyte imbalances and dilution of sodium in your blood (hyponatremia), which can manifest with symptoms similar to dehydration, such as headaches, nausea, and brain fog. A tell-tale sign that you are over-hydrating is that your urine is transparent, while it should be light yellow.

Why do electrolytes matter?

Electrolytes are minerals such as sodium, magnesium, potassium and calcium, which are essential for cellular communication and maintaining body fluid homeostasis. When sweating, we lose these minerals, so it is vital to replace them to rehydrate fully. It can be as simple as preferring mineral water over tap water or adding electrolytes to water when it's particularly hot or if we sweat a lot.

It is essential to select sugar- and colourant-free electrolyte replacement formulas, which are typically available in powder or liquid form. Another idea is to add a pinch of salt and some lemon juice to your water or drink coconut water, which naturally contains electrolytes. A dangerous trend I have observed is the consumption of distilled water, which is often considered “pure.” Distilled water is stripped of all electrolytes, which can create a severe electrolyte imbalance in the blood and all body fluids.

Is all water the same?

Tap water, despite being drinkable in most countries, can contain heavy metal residues as well as chlorine, which makes it unpleasant to drink. An option is to invest in a home filter to eliminate excessive residue, and if choosing a reverse osmosis filter, add back electrolytes. Mineral water is usually naturally sourced and contains different ratios of electrolytes and minerals, so it is a better choice than non-filtered tap water. 

Those are some facts from a nutrition professional on hydration and water intake, with the aim of bringing clarity amidst all the noise on social media. Balance is always the best bet, and while dehydration can be dangerous, overhydration can also be a risk. There is no need to force yourself to drink enormous amounts of water for no reason – follow your thirst signal, and if your urine is transparent, consider it a sign of overhydration.