FOR IMMEDIATE RELEASE
Drinking caffeinated beverages prior to exercising
unlikely to cause dehydration, expert says
Drinking caffeinated beverages prior to exercising unlikely to cause dehydration, expert says
New York, N.Y. – November 1, 2005 – There’s encouraging news for coffee lovers who value their exercise: caffeinated beverages do not lead to dehydration. In fact, caffeine may actually improve endurance and reduce fatigue in certain types of intense exercise.
This good news for runners, cyclists and other people who enjoy similar activity came from Lawrence Armstrong, Ph.D., Professor of Environmental Physiology in the Human Performance Laboratory at the University of Connecticut, Storrs. He spoke today at a workshop for health and science writers, Coffee: Breaking News about Health, Fitness and Performance, held at the Reebok Sports Club New York.
The physiologist first became intrigued with the caffeine-fluid retention conundrum by studying how he reacted to caffeinated beverages when he exercised. He told the editors, “Initially I observed my own body. When I drank beverages containing caffeine, I noticed that I always retained some of the fluid I drank. I thought, how could this be? That question led to my first article.”
In that article on caffeine and dehydration, he had compared the fluid retention properties of caffeinated beverages and water. He found that after beverage consumption, the percentage of fluid that the study volunteers retained was similar whether they drank caffeinated beverages or water. The researcher undertook the current study to determine how healthy male subjects reacted to different levels of controlled caffeine consumption, all considered moderate amounts. The young men were divided into three groups: one consumed capsules containing no caffeine, the second group had an amount of caffeine approximating two cups of coffee, and the third consumed caffeine in capsules equivalent to four cups of coffee. Subjects had no other sources of caffeine. Their fluid-electrolyte balance and kidney function, as well as other variables, were evaluated over 11 days.
According to Dr. Armstrong, “Several early studies showed that caffeine is a mild diuretic, but they were limited in their scope and duration. Although an hour or two after caffeine ingestion, diuresis (the increased secretion of urine) does occur, that does not mean that caffeine causes dehydration. There’s a difference between dehydration and diuresis.”
Both serious athletes and weekend athletes consume a number of beverages that, when taken in large volume, have a diuretic effect. It is interesting to note that scientists have shown that fluid-electrolyte replacement beverages have diuretic activity, and that even water is a diuretic.
Dr. Armstrong explained, “The idea that caffeine is a diuretic originated around 1930 with experiments on just a few humans and with animal research. The results indicated that caffeine causes an increase in urine production, which is true. But then, water does the same thing. Does that mean that we shouldn’t drink water?” At less than 300 mg a day, the diuretic activity of caffeine is similar to that of water.
Dr. Armstrong told the group, “For decades, health and exercise experts have cautioned that caffeine causes dehydration, despite a lack of scientific evidence to support that idea. It’s fair to ask why hospitals aren’t filled with dehydrated people. Our findings question the widely accepted notion that caffeine acts chronically to dehydrate the body.“
Armstrong, LE. Caffeine, body fluid-electrolyte balance, and exercise performance. International Journal of Sport Nutrition and Exercise Metabolism. 2002. 12:189-206 2002.
Armstrong LE, Pumerantz AC, Roti MW, Judelson DA, Watson G, Dias JC, Sökmen B, Casa DJ, Maresh CM. Fluid, electrolyte, and renal indices of hydration during 11 days of controlled caffeine consumption. International Journal of Sport Nutrition & Exercise Metabolism 15:252-265, 2005.