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It is less than 10 days until Christmas now and most of us in the Northern Hemisphere are still striving through these dark days. Fret not, Jonnie Jenkins is back and he is bringing Caffeine! Although, you might want to read on before you down too many cups of coffee.

Caffeine social

Caffeine is the worlds most commonly consumed psychotropic drug!

It is found in reasonable quantities in coffee, tea, cola and dark chocolate. The data from the graphs below are taken from an FDA study (U.S. Food and Drug Administration) into caffeine content of foods and drinks. The serving size in this case is 227.3 ml as the FDA still use fluid ounces not the SI units (International System of Units). The rest of the world use liters or milliliters as the standard unit of volume.


Brewed coffee generally contains about twice as much caffeine as brewed tea. As you can see the time of brewing has a large effect on the caffeine content.

The most prominent way the caffeine works in the body is to reversibly blocks the action of adenosine on its receptor and consequently prevents the onset of drowsiness. Caffeine at doses around  1 mg/kg has been seen to improve performance in endurance sports and there is evidence that higher doses (5 mg/kg) can improve sprint performance, cycling power output and cycling and running time trial performance.


However, to much caffeine can lead to caffeinism and caffeine dependency. These come with a wide range of unpleasant symptoms including nervousness, irritability, restlessness, insomnia, headaches, and palpitations after caffeine use. So think carefully before you incorporate caffeine in to you post Christmas training program!


Laszlo P. Somogyi, CAFFEINE INTAKE BY THE U.S. POPULATION. 2009, The Food and Drug Administration Oakridge National Laboratory, Available from: http://www.fda.gov/downloads/aboutfda/centersoffices/officeoffoods/cfsan/cfsanfoiaelectronicreadingroom/ucm333191.pdf

Ludwig, I. A. et al. Coffee: biochemistry and potential impact on health. Food Funct. 5, 1695 (2014).