Does your cup of 'joe' do you more harm than good?
One of the often-touted reasons for advising athletes not to consume coffee has been that it causes dehydration, which in turn can affect performance. This appears not to be true.
A June 2002 article written by a University of Connecticut researcher and professor, Lawrence E Armstrong, and published in the International Journal of Sport Nutrition and Exercise Metabolism concluded that caffeine is no more diuretic than water itself, and more recent research supports that finding.
Caffeine in coffee, and other beverages, has also been shown to produce performance benefits. Research shows that caffeine mobilises fat stores, helping to spare muscle glycogen during endurance training and competition, resulting in improved performance.
In longer races, it delays fatigue by preserving stored muscle sugar. Muscles get their energy from sugar and fat in the bloodstream, and from sugar, fat and protein stored in the muscles. When muscles run out of their stored sugar, they hurt and become more difficult to coordinate. Caffeine causes muscles to burn more fat, thus sparing stored muscle sugar to delay fatigue.
A study from the University of Birmingham in England has also shown that caffeine helps the body use more carbohydrates from drinks that you take during exercise (Journal of Applied Physiology, June 2006).
However, your regular cup of coffee may have a downside, particularly if you are a woman in peri or postmenopausal years and your daily calcium intake is lower than the recommended. Then your morning cup of coffee could be affecting the strength of your skeletal system.
In a report published in August 2002 by Creighton University in Nebraska, human physiological studies and controlled balance studies show a clear but small depressant effect of caffeine itself on intestinal calcium absorption. Low calcium intake is clearly linked to skeletal fragility, and it is likely that a high caffeine intake is often a marker for a low calcium intake.
There is no evidence that caffeine has any harmful effect on bone status or on the calcium economy in individuals who ingest the currently recommended daily allowances of calcium.
Your cup or three of coffee may be doing you more good than harm, but just remember to up your calcium intake by way of your diet (low fat yoghurt, cheeses etc) to counter any negative effects.
References:
http://ezinearticles.com/?expert=Gabe_Mirkin,_M.D.
Triathlon Magazine - July 2007 Jacobson
Science Direct - Food and Chemical Toxicology. Volume 40, Number 9. September 2002. pp1263-1278. Elsveir.