Originally Posted by rich007
Don't quote me on this one but I've read in many fitness mags that latest research on diuretic effects of coffee shows that it is
very mild diuretic... (IIRC, even Bicycling mentioned it also)...
I think where people make a wrong assumption is that "caffeine is diuretic" (which is true), so coffee has to have diuretic effects too, since it contains caffeine... What many disregard is that coffee also has plenty of water...
Coffee and Dehydration--Urban Myth
The logic goes like this: Diuretics cause dehydration. Caffeine is a diuretic. Coffee contains caffeine. Hence drinking coffee causes dehydration. The flaw in this logic is that coffee is NOT mostly caffeine, it is mostly water. The water provides hydration, while the small amount of caffeine has negligible or no effect. Many studies have shattered the myth about coffee and dehydration, but a recent thread in the newsgroup aus.bicycles showed that the scientific evidence apparently has not have reached everyone. Again, note the importance of distinguishing between the beverage of coffee, and the substance of caffeine; the small amount of caffeine in coffee is a diuretic, but it does not somehow eliminate the hydration effect of the large amount of water, or, according to several of the studies, diminish it at all. It is a shame that some people are giving up all the health benefits of coffee based on an urban myth. There are too many studies to list them all, but I've included some of them below.
The above quote is from here...
Coffee Lovers: Don't Worry About Dehydration
At lower amounts, such as 300mg/day the caffeine doesn't affect hydration status much, but at higher levels, and much more regular consumption of these levels I would still worry about the effects of caffiene. Plus, there's a dependency that can develop from this because it is, technically, a drug, and some racers can start to want the effects of caffiene all the time. One of the studies says that moderate caffeine consumption causes diruesis similar to that of water, but they talk about water consumption in large amounts, so that's a given, but to say that coffee is as good to rehydrate with as coffee just doesn't make sense. But it's like anything...moderate consumption is fine. Overdoing it is bad.