The genetics of caffeine

Caffeine is the most widely used performance-enhancing supplement around – and one of the few that actually works and is backed by solid evidence. But that doesn’t mean it works the same for everyone. Researchers have found variations in a single gene, known as cyp1a2, affect how long caffeine lingers in the body after providing its initial jolt. About half the population are fast metabolizers, clearing caffeine out of the body rapidly. The other half are slower metabolizers, with a small fraction being especially slow.

Recent work by University of Toronto researcher Nanci Guest, presented at the American College of Sports Medicine annual meeting, suggests that these differences inf luence how much caffeine boosts – or in some cases hinders – your endurance. She tested 100 athletes, putting them through a series of blinded 10k cycling trials with various doses of caffeine or a placebo. The 49 fast metabolizers improved their performance by an average of 1.2 minutes on the highest dose of caffeine; the 43 slower metabolizers improved by only 0.5 minutes (a statistically non-significant change); and the eight slowest metabolizers rode 2.5 minutes slower with caffeine.

Guest’s doctoral supervisor at the University of Toronto, Ahmed El-Sohemy, has launched a company called Nutrigenomix that offers testing for this and other gene variants. It’s worth noting that the cycling results are still preliminary, and the exact mechanisms aren’t clear. Still, with or without genetic testing, the study is an important reminder to consider your individual response to any training or nutrition intervention. Just because something works for “most people,” doesn’t mean it will work for you. The best solution: try it and see.