Filtered water or bottled water. From reading in too little light you get bad eyes and from late at night you become fat. We've heard it all before, but is it right? Kennislink dived into the world of medical myths and searched it out. This time: you have to drink two liters of water a day. A typical advice that you often hear: to stay healthy you need to drink at least two liters of water per day. Ask someone if they drink enough water and the answer is no. But is it really necessary to drink those eight large glasses a day? And where does that idea come from?
This myth is stubborn, but there is no scientific evidence that we should drink eight glasses of water a day. It is not entirely clear where the myth comes from. One of the first articles in which the numbers are mentioned is an article from 1933. It states that adults per kilocalorie they receive must drink 1 milliliter of water. Since men are advised to consume 2500 kilocalories and women 2000, that would mean that men should drink 2.5 liters of water and women 2 liters of water a day. The American research council (US National Research Council) adopted these figures in 1945 in a report. Is water healthy?
According to a 2002 article, the discussion must be about moisture and not about water specifically. Tea, lemonade, coffee and milk also contain water, so if you drink enough of it, you do not have to drink extra glasses of water. How much moisture you need exactly depends on many things. For example, from the heat. On a hot summer day or in the tropics you sweat more and you lose more fluid that needs to be replenished. Even if you do a lot of sport and exercise, you need more. What many people do not realize is that food also contains a lot of water. The Health Council gives the following advice: 70% of all the fluid that you ingest in a day must come from drinks, the rest is in your diet. In total they recommend to drink about 1.5 liters of fluid per day. The English recommend 1.2 liters of fluid per day.
Even slightly alcoholic drinks (up to 2% alcohol) help a dehydrated body to become hydrated again. Lemon water healthy and delicious.
That you have to drink an extra glass of water for every cup of coffee because you would dry it out, is also a familiar part of the myth. In a comparative study from 2000 researchers looked at whether people were less hydrated when they received their water from drinks with caffeine than when they drank water. That turned out not to be the case. Side note to that research: it was financed by a large shareholder in caffeine drinks: Coca Cola. A 2003 review came to the same conclusion (with financial support from a tea manufacturer). Even slightly alcoholic drinks (up to 2% alcohol) help a dehydrated body to become hydrated again. And what about the saying that you have to force yourself to drink because you are already dehydrated when you are thirsty? Nonsense. In 1982, scientists showed that we are already thirsty when our blood becomes 2% more concentrated. You are only dehydrated at a concentration increase of 5%.
Not drinking at all is of course not good. Especially if you do this during illness, exercise or severe heat, you can be dead within a few days. Drinking too little is also not convenient. You remember things less well, suffer and perform worse. But too much water is certainly not innocent. The kidneys can process about 0.7 to 1 liter of water per hour. Then water poisoning occurs. In 2005 a boy got into a coma because he had to drink six liters of water during a hazing. Children and drinking water.
Conclusion: two liters of water per day is not necessary. If you just drink when you are thirsty, you do not have to worry.
Balranald, Euston, Kyalite, Hatfield, Penarie, Clare, Oxley.