Alex Hutchinson draws on the latest research to answer your fitness and workout questions in this biweekly column on the science of sport.
Do I need to quaff protein shakes and powders if I want to gain muscle?
It's a pretty safe bet that the guy at the gym who is built like a tree trunk and bench-presses the entire rack also has an enormous barrel of protein powder tucked into his gym bag. This, you might think, is a pretty good endorsement of the "you've got to eat muscle to build muscle" school of thought.
But correlation is not the same as causation.
"It's hard to argue against years of practice that apparently works," says Stuart Phillips, a McMaster University researcher who studies protein needs in athletes. "The real question is, do they gain [muscle] because of what they do or in spite of what they do?"
On this basic question, athletes and scientists remain deeply divided. But there is increasing consensus on a range of related issues, such as when we need protein and what type is best.
At McMaster and elsewhere, researchers have spent years conducting careful studies of how much protein exercisers can actually use. By tracking nitrogen, which is found in protein but not in carbohydrates or fat, they can determine whether their subjects are building muscle, losing muscle or holding steady.
"We monitor the food going in and collect the poop, pee and sweat going out," explains Mark Tarnopolsky, one of Dr. Phillips's colleagues.
Surprisingly - but consistently - the results show that even serious athletes process only marginally more protein than their sedentary peers, and far less than the megadoses recommended by muscle magazines. Novice weightlifters use the most protein, since they are adding muscle most rapidly, while veteran bodybuilders use less despite their enormous muscles.
So, whose advice will you take: the egghead in the lab or the muscle-head in the gym?
Given the limitations of current research techniques, a middle path is likely most appropriate, Dr. Phillips says. While current dietary guidelines in Canada and the United States suggest consuming0.8 grams of protein per kilogram of body mass daily, there is reasonable evidence that 1.1 grams is appropriate for serious endurance athletes and 1.3 grams for serious strength athletes.
Even those amounts are below the 1.6 grams per kilogram of body mass that average Canadians tend to eat daily when their diet is unrestricted, Dr. Tarnopolsky says. That means an ordinary, balanced diet should easily meet your needs - unless you're restricting calories to lose weight. In that case, higher protein intakes (35 per cent of calories instead of 15 per cent, for example) combined with resistance training appear to help maintain muscle mass while overall mass drops.
Timing also matters: You'll build muscle more effectively if you take in protein within about an hour of finishing your workout. The optimal post-workout dose is about 20 grams, according to a McMaster study in the January issue of the American Journal of Clinical Nutrition. That's equivalent to about 600 millilitres of skim milk, four medium eggs or 80 grams of cooked beef. Powders, shakes and bars offer a convenient way to get this right after a workout - but then again, so does a tuna sandwich.
In the end, if you decide to side with the gym rats and supersize your protein shakes, it's unlikely to do much harm.
"The extra protein will, for the record, not pack your kidneys in and will not destroy your bones," Dr. Phillips says.
The main drawback is that, by taking too much protein, you might end up not getting enough of the carbohydrates that are crucial to performance in both endurance and strength athletes - and that risk should be enough to keep any smart athlete from overdoing the protein.
Alex Hutchinson blogs about research on exercise and athletic performance at http://www.SweatScience.com.