Dr Federica Amati, a world-renowned nutritionist, has challenged the long-standing advice to drink two litres of water daily. In a recent Instagram post, she argued that for most young, healthy people, hydration is not an issue and that listening to your thirst is the most effective way to stay hydrated.
What the Science Says
Dr Amati explained that the thirst response is a reliable indicator for most individuals. She noted that hydration becomes a concern primarily for the sick and elderly, whose thirst response may be dampened due to ageing. She emphasized that people do not need to force themselves to meet a specific daily target, as the body naturally signals when it needs water.
According to the NHS, adults should aim for six to eight cups or glasses of fluid per day, including water, lower-fat milk, and sugar-free drinks like tea and coffee. However, Dr Amati's advice suggests that this guideline may be too rigid for many.
Rehydration Salts: Use with Caution
Dr Amati also warned against the regular use of rehydration salts unless under extreme circumstances, such as after running a marathon or prolonged heavy sweating. She pointed out that these products are often high in sodium, which can contribute to hypertension and other health risks.
Water from Food
The nutritionist highlighted that a significant portion of daily water intake comes from food. Eating whole fresh fruits and vegetables can substantially contribute to hydration levels, reducing the need to rely solely on drinking water.
Individualised Hydration Needs
A Nuffield Health expert noted that the right amount of water depends on the person and their environment. Drinking too much water can lead to loss of valuable minerals like salt and potassium, while drinking too little can cause minerals to crystallise and form kidney stones.
The expert recommended a simple formula: aim for about 35ml of water per kilogram of body weight. For example, a person weighing 72kg (159lbs) should target around 2.5 litres per day, someone weighing 85kg (188lbs) needs about three litres, and a 100kg (220lbs) individual requires approximately 3.5 litres. These amounts may increase with an active lifestyle, frequent exercise, or exposure to hot conditions.
Key Takeaways
- Listen to your thirst rather than forcing a specific volume.
- Hydration needs vary by age, body size, activity level, and diet.
- Food, especially fruits and vegetables, contributes to hydration.
- Avoid routine use of rehydration salts due to high sodium content.
- General guideline: 35ml of water per kilogram of body weight, adjusted as needed.
