According to nutritionist Dr Federica Amati, the widely held belief that everyone needs two litres of water a day is a myth. Instead, she advises that for most healthy people, the best guide is simply to drink when thirsty.
Thirst Is the Best Indicator
Dr Amati, a registered nutritionist with a PhD and MSc, shared her insights on Instagram, stating: "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?" She explained that for most young, healthy individuals, hydration is not a concern. However, hydration can become an issue for those who are sick or elderly, as their thirst response is dampened due to normal ageing.
Rethinking Hydration Goals
The NHS recommends six to eight cups or glasses of fluid daily, including water, lower-fat milk, and sugar-free drinks like tea and coffee. But Dr Amati argues that forcing a fixed amount like two litres is unnecessary. She advises against regular use of rehydration salts unless after extreme exercise like a marathon, as they can be high in sodium, a risk factor for hypertension.
Food Contributes to Hydration
Dr Amati emphasised: "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." This means a balanced diet naturally supplements fluid intake.
Individual Needs Vary
An expert from Nuffield Health noted that the right amount of water depends on the person and their environment. Drinking too much can lead to loss of valuable minerals like salt and potassium, while too little can cause mineral crystallisation and kidney stones. A general guideline is about 35ml of water per kilogram of body weight. For example, someone weighing 72kg (159lbs) should aim for approximately 2.5 litres per day; 85kg (188lbs) needs about 3 litres; and 100kg (220lbs) requires around 3.5 litres. These amounts may increase with activity or hot weather.
