Caffeine provides a life-affirming jolt in cubicles the world over.
But could it also give athletes an edge?
That’s the question being answered by Toronto scientists, who are closer to defining the relationship between caffeine and genetics when it comes to improving athletic performance. Their research, which will be published in an unnamed science journal next month, could have ramifications in the sporting world.
Especially for endurance athletes, the area of athletic performance that the University of Toronto researchers show is most improved by caffeine, compared to power and strength where adrenalin may play a bigger role.
“Whether to take caffeine or not is a big deal for millions of athletes,” says lead researcher Nanci Guest, a sports dietitian studying “nutrigenomics,” the interaction of nutrition and genes. “The fact that some may do worse is important information for competitive athletes worldwide.”
The relationship between athletes and caffeine returned to the spotlight last month when the World Anti-Doping Agency confirmed caffeine is on the “waiting list” for prohibited substances. In fact, caffeine has been part of the WADA monitoring program since it was removed as a banned substance in 2003.
Genetically caffeine isn’t for everyone. A gene called CYP1A2 determines how fast we metabolize caffeine — the faster the better for receiving a performance boost.
“Some people can process (caffeine) easily and others not so much,” says Greg Wells, an assistant professor of kinesiology at U of T.
Guest’s research was conducted in Wells’ lab where 100 subjects underwent genetic testing to determine whether they metabolize caffeine quickly or slowly. The test by Nutrigenomix Inc. is the only way to know who is a fast or slow caffeine metabolizer. How soon a coffee drinker is able to fall asleep after a cup isn’t an accurate barometer. It costs upwards of $250 and is available at many clinics across Canada.
Of the 100 subjects participating in the researchers’ endurance test, half of them (50 per cent) metabolized the stimulant quickly and performed better in 10-km cycling time trials on caffeine than when given a placebo. Ten per cent metabolized caffeine more slowly and performed worse on caffeine than on a placebo. The performance of the remaining 40 per cent of test subjects was basically the same whether they were given caffeine or a placebo. Researchers gave the test subjects precise doses of 2 or 4 mg of caffeine per kg of body weight in pill form, rather than brewed coffee.
For those who benefit from the effects of caffeine, the enhancement happens in the central nervous system. Caffeine blocks the calming affect of chemical messengers called adenosine receptors. So the discomfort of effort and pain in the muscles is reduced allowing for a greater intensity of exercise without the greater amount of pain.
The benefit of caffeine in sport could also depend on which sport the athlete plays. A shooter in basketball may not see the need, says Wells.
“If you need to be calm and relaxed, it’s definitely not something you would be using for your performance,” says Wells. These results show a benefit for some endurance athletes. “If you’re doing a bicycle race or a 1,500-metre run, it might be very powerful.”
But that doesn’t mean athletes should guzzle as many “Venti” Starbucks coffees as they can stomach before competition. In fact, this extra-large coffee (20 oz or 591 mL) is probably way too much caffeine.
“That would be the absolute crazy upper limits of what I could consider to be safe,” says Wells, who would recommend up to two cups (16 oz or 473 mL) of coffee instead.
Too much caffeine for those who metabolize the drug slowly can increase their risk of heart attack and high blood pressure since it stays in the body longer, says Toronto researcher Ahmed El-Sohemy, a nutritional scientist who supervised Guest’s research. He has studied caffeine and heart health, and is the founder of Nutrigenomix, which provides the genetic testing services.
Conversely, fast metabolizers of caffeine appear to have a decreased risk of heart problems associated with up to three cups of coffee a day, he says.
“Unless you know your genetics for caffeine metabolism, you should limit your intake to no more than two small cups of coffee per day,” says El-Sohemy. When he says small cups, he means two 8 oz (236 mL) cups or the size of two “Short” cups or one “Grande” at Starbucks.
A Venti coffee habit isn’t just unhealthy but is more caffeine than necessary to get an athletic boost. For a 70 kg (154 lb.) athlete who metabolizes caffeine quickly, about 280 mg of caffeine is enough, says Guest. That’s 4 mg of caffeine per kg of body weight, which is the amount used in her research.
A 20 oz (591 mL) Starbucks Venti coffee, has 340, 410 or 475 mg of caffeine depending on the roast (the lighter the roast, the greater the caffeine content). A 16 oz (473 mL) Grande has at least 260 mg of caffeine, and a 12 oz (354 mL) Tall has at least 193 mg of caffeine, according to company nutrition information. Tim Hortons’ original blend coffee ranges from 140 mg (small) to 330 mg (extra large) of caffeine, according to its data, though Guest found that the amount of caffeine in each cup can vary. She used caffeine powder to standardize the dose for her study.
“It looks like somewhere between two and four (mg of caffeine per kg of body weight) seems like the magic dose that’s going to work for most endurance athletes,” says Guest.