A new study has found that ingesting as little as five grams of protein after physical activity is enough to achieve a positive protein balance, which is a prerequisite for growth in healthy, active children. The study, published in the Journal of Nutrition in April, is the result of collaborative research between Professor Daniel R. Moore of U of T’s Faculty of Kinesiology and Physical Education and his colleagues at McMaster University and the Nestlé Research Centre in Switzerland.
“The growth of bone and muscle in children is related to how their body breaks down old proteins and rebuilds new ones. In order for children to grow, the balance between synthesis and breakdown has to be positive,” says Moore. “We knew that for adults to be in a positive protein balance, especially after exercise, they have to consume protein, but we didn’t know if that was also the case in children and, more importantly, how much protein children might need.”
The children in the study were given zero to 15 grams of protein following a bout of exercise modelled after a hockey game. After taking their blood and breath samples, the researchers determined that the children who didn’t consume any protein over three hours after exercise stayed in a negative protein balance.
“This doesn’t mean that they were losing muscle mass, but they weren’t gaining any, either,” says Moore.
On the other hand, the children who consumed just five grams of protein over three hours after exercise achieved a positive protein balance, which supports lean body mass growth. The children who consumed greater amounts had a proportionally greater increase in protein balance.
The next step for science, according to Moore, would be to determine whether the effects of ingesting protein would be the same if done right after exercise or three hours later. And, could this greater protein balance be sustained over several days or even weeks? Finding answers to these questions could translate into more accurate recommendations for the optimal growth and development of lean body mass in children with an active lifestyle.
For now, Moore suggests giving your child a snack with a bit of protein after any kind physical activity in which energy is expended, from vigorous play to hockey practice. A protein-free sports drink or juice won’t cut it, but 250 ml of milk translates into eight grams of protein – three grams more than the minimum amount of protein found to strike that positive protein balance after exercise.
“But, before you give your kids the all clear to drink chocolate milk all day, remember that exercise should come beforehand, as this will be the most important factor to stimulate growth of muscle and bone,” says Moore.