Lab Rat

Does Caf­feine Re­ally Im­prove Per­for­mance?

Canadian Running - - CONTENTS - By Alex Cyr Alex Cyr is a na­tive of P.E.I. He cur­rently lives in Wind­sor, Ont.

“We want to learn more about these ge­netic vari­a­tions be­tween peo­ple, and how cer­tain food con­stituents might help cer­tain in­di­vid­u­als un­lock a greater ge­netic po­ten­tial.”

Sip­ping on a fresh brew, gulp­ing an en­ergy drink or pop­ping a caf­feine tab in the hour be­fore a race has be­come com­mon prac­tice for run­ners look­ing to gain an ad­van­tage over their com­peti­tors. Am­a­teur and pro­fes­sional run­ners alike swear by the sub­stance, but do we know for sure if it even pro­vides an er­gogenic ef­fect?

Thanks to the re­search of reg­is­tered di­eti­tian and PhD can­di­date Nanci Guest, her col­leagues at the Univer­sity of Toronto and Nutrigenomix, a ge­netic test­ing firm based in Toronto, we now know that run­ners may want to fa­mil­iar­ize them­selves with their ge­netic makeup be­fore mak­ing a pre-run pit­stop at their lo­cal Tim Hor­tons.

Guest’s study in­ves­ti­gated whether vari­a­tion in the cyp1a2 gene, which de­ter­mines the speed at which an in­di­vid­ual me­tab­o­lizes or breaks down caf­feine, af­fected an ath­lete’s re­sponse to caf­feine sup­ple­men­ta­tion dur­ing en­durance ex­er­cise. The study in­cluded 101 com­pet­i­tive male ath­letes who were cat­e­go­rized as AA, AC or CC geno­types. In a ran­dom­ized dou­ble-blinded placebo-con­trolled de­sign, par­tic­i­pants cy­cled 10k un­der three dif­fer­ent con­di­tions: hav­ing con­sumed zero, two, or four mil­ligrams of caf­feine per kilo­gram of body weight. The dif­fer­ences in per­for­mance, rang­ing from much faster to much worse dur­ing caf­feine con­di­tions com­pared to placebo, helped to un­cover the rea­sons for the in­con­sis­tent re­sults seen in caf­feine-ex­er­cise stud­ies.

“My study showed that ba­si­cally not all ath­letes ben­e­fit from caf­feine,” says Guest. “Through a sim­ple saliva test, we can iden­tify ath­letes as slow or fast me­tab­o­liz­ers of caf­feine. These vari­a­tions have been im­pli­cated in dif­fer­ent per­for­mance out­comes to en­durance ex­er­cise un­der con­di­tions of placebo ver­sus caf­feine.”

Ath­letes found to have the AA geno­type (fast me­tab­o­liz­ers of caf­feine) ex­pe­ri­enced a per­for­mance ben­e­fit and were 4.8 per cent faster when in­gest­ing a low dose (2 mg/kg) and 6.8 per cent faster un­der the moder­ate dose (4mg/kg of caf­feine. Con­versely, when ath­letes with the CC geno­type con­sumed 4 mg/kg they were 13.7 per cent slower com­pared to when they con­sumed the placebo. No ef­fects on per­for­mance were ob­served at ei­ther dose in those with the AC geno­type. “Think of it as a traf­fic light,” says Guest. “If you are a CC, stop at caf­feine. If you are an AC, pro­ceed with cau­tion, and if you are an AA, try caf­feine, as you’re likely to see a sub­stan­tial per­for­mance boost.”

Nutrige­nomics, the science of how in­di­vid­u­als re­spond dif­fer­ently to foods, nu­tri­ents and sup­ple­ments based on their ge­net­ics, helps sci­en­tists un­der­stand the im­pli­ca­tions of ge­netic vari­a­tion when re­act­ing to cer­tain foods, such as that which is seen in lac­tose and gluten in­tol­er­ances. With some re­searchers in the field fo­cus­ing on the in­ter­play be­tween food, genes and sport per­for­mance, like Guest, ath­letes are gain­ing knowl­edge, and are now able to tai­lor their food in­take to their in­di­vid­ual needs. “Nu­tri­tional stud­ies that do not take into ac­count ge­netic makeup are of­ten in­com­plete, be­cause we see re­search re­ported as the aver­age of what hap­pened in the study group as op­posed to look­ing at in­di­vid­ual data,” says Guest. “In our lab, we want to learn more about these ge­netic vari­a­tions be­tween peo­ple, and how cer­tain food con­stituents might help cer­tain in­di­vid­u­als un­lock a greater ge­netic po­ten­tial.”

As for caf­feine in par­tic­u­lar, Guest ad­mits that more re­search is needed on how dos­ing and tim­ing af­fect per­for­mance. Lower doses seem to be the way of the fu­ture, as they are ef­fec­tive and can help avoid some of the ad­verse ef­fects of higher doses.

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