Do coffee and tea affect the dehydration of the body?
Every day people around the world drink 1.6 billion cups of coffee and twice as much tea. People like the taste of these drinks and they are confident that caffeine helps them to wake up.
However, when doctors insist that we have to drink from six to eight glasses of water daily, they always emphasize that coffee and tea are not in the list. They generally even cause dehydration of the body.
Do researchers support this widespread recommendation?
Although tea and coffee contain different substances, most studies tend to refer to caffeine. But such a consideration is so dubious that one of the most popular experiments was conducted in early 1928, and there were three people involved in it.
Three men were watched over two winters. Sometimes they were asked to drink four cups of coffee every day, sometimes they drank mostly tea, and on other days they did not drink tea or coffee, sometimes only water with the addition of pure caffeine.
During the experiment, scientists regularly measured the amount of participants’ urine in the experiment. The authors came to the conclusion that when men drank water with caffeine, after a two-month hiatus in the consumption of coffee or tea, the volume of their urine increased twice. And when they were drinking coffee regularly, the amount of urine remained at the usual level.
Large doses of caffeine are known to increase the flow of blood to the kidneys and block the absorption of sodium, which explains why it has a called a diuretic effect. But this issue is still the subject of scientific discussion.
However, when it comes to researching realistic quantities of caffeine, its diuretic effect is far from obvious.
A review of Ten Research by Lawrence Armstrong of the University of Connecticut showed that caffeine has a rather weak effect compared with other diuretics. In 12 out of 15 experiments, the volume of urine was not increased after drinking water with caffeine.
Then, why so many people are convinced that coffee and tea make them use the toilet more often?
As the survey shows, in most studies, participants drank pure caffeine, not tea or coffee, as we do in life.
Perhaps the combination of substances contained in coffee and tea, affect the other result?
One exceptional study found that people who only drank tea during the 12-hour experiment had the same level of fluid in the body as those who drank the same amount of boiled water.
As for coffee, one study indeed showed an increase of 41% in urine, as well as a higher proportion of sodium and potassium. However, these participants refrained from consuming caffeine before the experiment, so these data are unlikely to show an objective picture for those who drink coffee regularly.
The results of another study are even more controversial. Comparison of the level of liquid after consumption of coffee and water did not show any difference at all.
So, although we notice that the need for emptying increases after drinking coffee, the mistake is that we compare our feelings with the period when we did not drink anything at all, and not with the time when we drank water or another drink.
If you drink a glass of water instead of a cup of tea, the effect is likely to be the same.