Forget what you may have heard -- despite caffeine's effects in making you want to urinate, a small new study shows that moderate coffee consumption does not cause people to become dehydrated.
The research was funded by the Institute for Scientific Information on Coffee, which is a nonprofit organization. It should be noted that European coffee companies -- including illycaffe and Nestle -- are members of the ISIC. However, ISIC did not have a role in the study design or analysis.
The study, published in the journal PLOS ONE, involved having 50 men drink four mugs of black coffee or four mugs of water a day for three days. Then, after a 10-day "wash-out" period, the men who initially drank black coffee instead drank water for three days, while those who drank water then drank the black coffee for three days.
University of Birmingham School of Sport and Exercise Sciences researchers analyzed the participants' hydration status after both the water-drinking and coffee-drinking periods by looking at their total body water and body mass. They did not find that there were any significant differences between the water-drinkers and the coffee-drinkers. There were also no differences in urine volume or concentration.
Researchers said they conducted the study to evaluate the persistent myth that coffee causes dehydration because caffeine can act as a diuretic, and that past research had been thin and inconclusive.
The Mayo Clinic has pointed out in the past that normal consumption of caffeinated drinks can actually contribute to daily fluid requirements, and that any effects caffeine may have on making you need to urinate likely won't lead to dehydration.