Milk beats soy for muscle gain
The study, conducted by a team of researchers at McMaster's Department of Kinesiology, was recently published in the American Journal of Clinical Nutrition. It compared how much muscle protein young men gained after completing a heavy weight workout followed by consumption of equivalent amounts of protein as either fluid skim milk or a soy drink.
"Our thinking going into the study was that milk would be better than soy," says Sarah Wilkinson, lead researcher and a graduate student in the Department of Kinesiology. "We suspected this would be the case because of work done by French researchers. However, we were really impressed by how much greater the gains in muscle protein with milk were."
The findings would suggest that if men consume only skim milk (two cups) after each of their workouts, they would gain almost twice as much muscle in 10 weeks than if they drank the same amount of protein as a soy drink.
"This is an interesting finding, since soy and milk proteins are considered to be complete proteins that are basically equivalent from a nutritional standpoint," explains Stuart Phillips, associate professor of kinesiology, who was also involved in the study. "Our findings clearly show that milk proteins are a superior source of protein in producing muscle mass gains in response to weightlifting."
Scientists also analyzed the composition of milk and soy proteins and did not find remarkable differences. At this stage, researchers are uncertain why milk proteins were so much more effective than soy. However, the two main types of proteins in milk, whey and casein, may have intrinsic properties that are advantageous for supporting muscle growth.
"The plan at this point is to follow this up with a long-term study to see if the findings from this short-term study can be replicated," says Phillips.
Funding for the study was made possible by the Canadian Institutes of Health Research (CIHR) and the US National Dairy Council.