First, I would like to say the information I am about to present is largely anecdotal. I have no scientific evidence to suggest that the claim I am making is true, but it does explain an issue I have encountered. I postulate that excess coffee consumption negatively affects athletic endurance.
Over the last few months, I have been having difficulty finishing bike races I would otherwise do well in. This includes races at the Forest City Velodrome in London, ON, the Midweek Crit in Mississauga, ON, and the Larkenville Challenge in Buffalo, NY. Nevermind, a poor performance down in Georgia at Speedweek. I was getting spit out the back in races I should have finished with the pack. Part of the issue has been mental: I've not really wanted to race this season, so there have been times I just dropped out of a race. However, when I wanted to finish, I found that I could not. Two weeks ago, in Buffalo, I lasted 30 mins in the 65min race because I had nothing left: literally. The following Tuesday at the Midweek Crit, the same thing happened. Around the 30 min mark, I was blasted. Both races averaged 43km/h but I've done Midweek last year when it averaged 45km/h. This should not have been hard, but for some reason it was. With Midweek, I used to be able ride to work, ride to the race, do the A and B races, and ride home without issue. 100km in a day with a race in the middle. For some reason, this year, something changed. It is the "what" that changed I could not figure out. All this sudden inability also played havoc on my will to race. I was losing interest. Then, I a friend ask me: what changed? And, I got to thinking.
Ok, so in December I moved to Milton, ON from Toronto, ON and I was no longer commuting 30km/day to work and back. That could not be it - if anything the daily grind did more to tire me out that anything else. In December, I bought an espresso machine because in Milton, there are more Starbucks outlets than Tim Hortons, and I was spending $10/day on coffee. Could that be it? Another friend did tell me that she had found that coffee lead to tiredness because it can cause low blood iron levels.
You see, I use to be a stanch tea drinker and only had an espresso based drink once and a while until I bought the espresso machine. I found years ago, caffeine causes all kinds of problems, and I tried to keep my caffeine consumption low. I never thought drinking decaf coffee could cause any issues because black tea and decaf coffee have about the same amount of caffeine. However, with the new espresso machine, I was consuming upwards of 5-10 shots of espresso per day. It's decaf, so it can't be that bad, right?
Using the highly scientific research tool, Google, I went looking for answers. I looked up the side effects of coffee. There are two that stuck in my mind. Coffee interferes with the absorption of iron. Iron is used by blood hemoglobin (red blood cells) to help carry oxygen. The acid in coffee causes a laxative effect in the intestines such that food may be fully processed before being ejected. The darker the roast of the coffee the higher the concentration of acid (and I like dark coffee). This means that I would eat, drink coffee, and soon find myself in the washroom. I didn't think much of it at the time.
The result: cut the coffee consumption. I cut to max 2 shots of espresso per day or less...generally, one at at time. I started to eat more red meat and added spinach to my diet with the idea of getting the iron count up if indeed it was down. It seemed to work. I had legs the entire race this weekend at the Midweek Crit for the full 60mins. I had legs for more of the 75mins of the Larkenville Challenge. Whereas with the coffee overload, my endurance seems to be shot, off coffee, it seemed to return.
Again, this wasn't a scientific study. If you know of research studying excessive coffee consumption on athletic endurance, please send it to me.