It's one of those coffee factoids that everyone "knows": coffee dehydrates you. Or, more precisely, caffeine functions as a diuretic, and therefore contributes to dehydration. A new coffee study
from the University of Birmingham (UK) suggests that the dehydrating effect of coffee is nothing more than an oft-reported myth based on a single study conducted in 1928
. So what's the new skinny on coffee and dehydration?
In a nutshell, say the researchers, coffee provides as much hydration as drinking an equivalent amount of water. The team had 50 adult men drink four cups of coffee a day for three days, then switch and drink four cups of water a day for three days. They ate the same foods, and were prohibited from drinking alcohol and vigorous exercise for the duration of the study. The scientists found no differences in hydration between the coffee-drinking days and the water-drinking days, nor was there any difference in urine output -- is that TMI?
It's important to note that the study specifically recruited regular coffee drinkers -- those who habitually drink three to six cups of coffee a day, and that the human body develops a tolerance for the effects of caffeine over time. It's possible, of course, that someone who doesn't drink coffee often might be more subject to the diuretic effects of the caffeine in coffee.
Coffee and Memory
Do you have trouble remembering what you had for breakfast yesterday? Another study suggests that coffee may just help you out there, too. Researchers at Johns Hopkins University took a look at how caffeine affects midterm memory. Participants viewed a series of images as part of a task without being told that they would be trying to recall those images later. Immediately after the exercise, they took either 200 mg of caffeine, or a placebo. The next day, the participants were shown another series of images, some of which they had seen in the previous exercise. This time, they were asked to identify which images were new and which they'd seen the previous day. Those who had taken caffeine tablets were more likely to recognize the images they'd already seen. According to the scientists, the results suggest that caffeine may help fix experiences or knowledge into memory.
About Those Antioxidants...
Sometimes when we're hunting down info on one thing, we come across other interesting tidbits, like this three year old Canadian study on coffee and antioxidants
. It was published SpectroscopyNow.com, and compared antioxidant activity between green and roasted coffee beans. Scientists at the University of British Columbia Vancouver discovered that, contrary to previous belief, the antioxidants found in coffee aren't inherent in the bean. Instead, they are actually a product of the Maillard reaction, which happens during the roasting process. To be more precise, while green coffee beans show higher antioxidant activity than roasted coffee beans, the activity comes from chlorogenic acid, which decreases by as much as 90% during roasting. The antioxidant activity in roasted coffee beans comes largely from compounds created by the roasting process itself. Oh, and the most intriguing sentence of the article is saved for the end:
Quite bizarrely, some research has suggested that simply breathing in the aroma of roasted coffee beans can provide a dose of antioxidants...
If that's the case, people who work in coffee shops and roasteries could have some of the best antioxidant protection available.