A nutritionist and a Nuffield Health expert have challenged the widely-held belief that two litres of water a day is the right amount for everyone. The latest heatwave has left numerous people feeling dizzy, faint and exhausted, making adequate hydration essential.
NHS guidance and expert doubts
The NHS recommends consuming six to eight cups or glasses of fluid daily to keep your body functioning properly. "Water, lower-fat milk and sugar-free drinks, including tea and coffee, all count as part of your daily intake," according to the national health service.
Yet Dr Federica Amati, a nutritionist, has taken to social media to question whether the two-litre daily water requirement applies to everyone. She shared on Instagram: "You may have heard you need two, three or maybe even four litres of water a day, but how much water do we actually need to drink?"
Thirst cues and food intake
According to her, the best approach for most individuals is simply responding to your body's natural thirst cues to stay hydrated. This involves drinking when you feel thirsty, rather than fixating on hitting a specific two-litre daily target.
The doctor added: "We have to remember that we get a lot of the water we need from our food, which is why eating whole fresh fruits and vegetables really contributes to your hydration levels." She also advises that rehydration salts are only necessary after running a marathon or sweating profusely for extended periods, warning against making them a daily habit due to their elevated sodium content.
Individualised water needs
A Nuffield Health specialist explained: "Just like determining how much water is right for you, this all depends on the person and the environment they live in. If we drink too much water, we risk losing valuable minerals like salt and potassium in our urine. If we drink too little, these minerals can start to crystallise and form kidney stones."
The specialist suggested a simple guideline: "Aim for around 35ml of water per kilogram of body weight." For someone weighing 72kg (159lbs), that's approximately two and a half litres per day; for 85kg (188lbs), around three litres; and for 100kg (220lbs), roughly three and a half litres. Needs may increase for those who are particularly active or in warmer climates.
