After each cup of coffee should also drink a glass of water, because coffee “drives”, so often well-intentioned advice. But is it true that coffee draws water from the body and thus does not count toward fluid intake? No, according to the DGE’s answer. While there is no harm in drinking a glass of water with a cup of coffee, it is not necessary. For many people, coffee makes a significant contribution to their total daily water intake. It is included in the fluid balance – just like any other drink, such as a glass of juice, a cup of tea or a glass of beer in the evening.
Caffeine effects
It is true that caffeine contained in coffee has a diuretic effect. Both the amount of caffeine and the frequency of coffee consumption have an effect on this. However, the effect is only temporary and less pronounced with regular coffee consumption, so that fluid balance is restored within a day.
At higher caffeine concentrations, the high caffeine intake leads not only to increased water excretion but also to increased salt and especially sodium excretion. This effect is also regularly compensated by compensatory mechanisms.
Because of its stimulating effect on the heart and circulation, coffee should not be used to quench thirst, according to the DGE recommendation. Mineral and drinking water and other low-calorie beverages, such as spritzers made from fruit juice and water, as well as fruit and herbal teas, are better alternatives here. However, there is nothing against the moderate consumption of up to 4 cups of coffee per day with 350 mg of caffeine.
Does coffee dehydrate the body?
When consuming a few cups of coffee once, 24 hours are sufficient to compensate for the low diuretic effect of caffeine within 3 to 7 hours by counter-regulatory mechanisms. Coffee therefore influences fluid balance in the medium term solely through the amount of water supplied with the beverage.
The recommendation to drink a glass of water with each cup of coffee was based, among other things, on the misinterpretation of the results of a study in which the total amount of water was used as the sole measure for assessing hydration:
In 12 volunteers who had not drunk coffee for five days, consumption of six cups of coffee on the day of the experiment resulted in an average decrease in body weight of 0.7 kg and a concomitant increase in urine volume and sodium excretion.
The conclusion of coffee as a fluid predator is based on a misconception that equated the transient decrease in body weight, and thus total body water volume, with a deterioration in hydration. However, this decrease does not necessarily represent a deterioration in hydration. A water or fluid deficiency is characterized by factors such as an increase in urine concentration (number of dissolved particles, osmolality) and increased electrolyte excretion.
Conclusion
If coffee is consumed regularly in a constant amount, there is no increased excretion of water as well as sodium as a result of increased activity of various compensatory mechanisms.
