The recommendation to drink 2 liters of water a day (about 8 glasses) can be heard both from ordinary people and from nutritionists. Most are sure that drinking this amount of clean water is the basis of proper nutrition and a healthy lifestyle.
Although, in general, this statement is more likely to be true than false – there are many reservations. First, you need to consider the liquid contained in the food. Secondly, water consumption standards depend on several factors and vary from person to person.
2 liters of water per day – where does the figure come from?
Let us immediately note that the opinion that each person needs to drink exactly 2 liters of clean water per day is currently considered outdated. The figure was proposed in 1945 – and over the past years, the understanding of the mechanisms of metabolism has fundamentally changed.
Initially, it was said that each kilocalorie of food eaten requires approximately 1 g of water during digestion. Considering that the average calorie intake is 2000 kcal, this is precisely the 2 liters of water per day that you need to drink.
In 1989, fundamental amendments were made to the recommendations. According to research, about 70% of the daily fluid requirement is covered by vegetables, fruits, soups, and other foods – that is, the diet directly affects the norms of water consumption.
Modern understanding
First of all, over the past years, the amount of liquid required to digest calories has been clarified – although the figure varies, it is more correct to talk about 1.5 g of water required to absorb 1 kcal. This increases the recommended amount by about 50%.
What affects the rate of water consumption:
- body mass
- physical activity level
- ambient temperature and humidity
- clothing density
- diet (including alcohol consumption)
How much water should you drink – WHO standards
According to the manual of the World Health Organization, the key problem in determining the norm of fluid intake in proper nutrition is the need to take into account secondary factors. That is, it is impossible to name one universal figure that suits absolutely everyone.
For example, a man weighing 70 kg and leading a sedentary lifestyle needs about 2.5 liters of water per day; a woman weighing 58 kg – 2.2 liters of water per day. With active physical work (or sports), needs can increase to 4.5 liters and above.
Table of liquid consumption rates:
| Body Weight | Water norm (liters) | Water norm (glasses) |
| 45 kg | 1.5 l | 6-7 glasses |
| 50 kg | 1.6 l | 6-7 glasses |
| 55 kg | 2.0 l | 6-8 glasses |
| 60 kg | 2.2 l | 7-8 glasses |
| 65 kg | 2.4 l | 7-8 glasses |
| 70 kg | 2.5 l | 7-9 glasses |
| 75 kg | 2.7 l | 8-9 glasses |
| 80 kg | 2.9 l | 8-9 glasses |
| 85 kg | 3.0 l | 8-10 glasses |
How to calculate actual water consumption?
The presented figures must imply the total consumption of liquids during the day – that is, not only pure drinking water in glasses but also water in various drinks and food products.
It is estimated that the average person drinks about 1.04-1.63 liters of pure water per day – the body gets the rest (up to 70%) from other sources of fluid.
That is, in practice, the exact amount of fluid required by the body cannot be measured with glasses of clean water. In addition, the volume of glasses varies.
How much water should you drink while playing sports?
Strictly speaking, scientific work on daily fluid intake standards is devoted primarily to the needs of people in active physical work (including military service) and during prolonged sports activities – while people with a sedentary lifestyle are considered less often.
In these cases, we are talking about the fact that insufficient water consumption can hurt both overall performance and the health of the body. Especially at elevated temperatures and high humidity.
Fluid standards for athletes
Usually, we are talking about the fact that athletes need about 2 times more water than people with a sedentary lifestyle – and the figure is about 4.5-5 liters per day for men and women.
Directly during training, liquid can be consumed in the amount of 0.8 liters per hour – and it is preferable not just water, but a drink with electrolytes.
Electrolytes (magnesium and calcium in particular) are needed by the body to transmit nerve impulses, contract muscles, and regulate blood pH levels—importantly, the body loses them more quickly through sweating.
The volume of liquid a person needs cannot be measured in glasses—most water is consumed in food and other drinks. In addition, the norms depend on body weight, activity level, and temperature – in some cases increasing by 2 or more times.