I found out today in class (Radiation Biology, Grad School at McMaster in Hamilton, ON - we have our own reactor!) that caffeine sensitizes cells to radiation damage, especially that done by UV light. It’s thought that the caffiene inhibits DNA repair mechanisms. My prof figures the amount of caffeine used is equivalent to about 20 cups of coffee. So anyone with a stack including lots of caffeine, stay out of the sun! Or tanning beds… : )
I had actually read that damage was seen in cells upon introduction of caffeine equivalent to 100 cups of coffee. Either way, I believe that damage was not seen in normal doses (even as something of a caffeine junkie, 20 cups of coffee seems excessive).