Aug. 8, 2007 -- Drink milk after your weight training workouts, and you may gain more muscle and lose more body fat than if you drink a soy or carbohydrate drink, according to the results of a new study.
Researchers compared the effects of drinking nonfat milk, a soy protein drink, or a carbohydrate drink on building muscle and burning fat after completing weight lifting workouts.
All three groups gained muscle, but the milk drinkers got the best results, says researcher Stuart M. Phillips, PhD, associate professor of kinesiology and an exercise physiologist at McMaster University in Hamilton, Ontario, Canada. The study was funded by the National Dairy Council and published in the Aug. 1 issue of the American Journal of Clinical Nutrition.
Phillips and his colleagues recruited 56 healthy young men, average age 22, and assigned them to drink milk, a soy drink, or a carbohydrate drink immediately after their weight training exercises and then an hour later. "They drank 2 cups each time," Phillips tells WebMD.
The drinks were all vanilla-flavored, served in opaque containers, and had an identical number of calories --178 per serving. The milk and soy drinks were matched for protein, fat, and carb content. Each had 18 grams of protein, 1.5 grams of fat, and 23 grams of carbohydrate.
Participants weight-trained five days a week for 12 weeks, and all the participants were novices. They had not done any weight training for the past eight months. The exercises were done on standard weight training machines, which worked out all the major muscle groups, with participants increasing repetitions as they gained strength. Each session lasted about one hour.
At the study start, the researchers measured each participant's body composition, noting the amount of lean mass and fat mass. They repeated the measurements at the end of the study.
The milk drinkers gained the most muscle. "The gains of muscle in the milk group were 8.8 pounds, vs. 6 pounds for the soy group, vs. 5.3 pounds for the control group [drinking the carbohydrate drink]," says Phillips. "The group that drank the milk gained 60% more muscle than the carbohydrate group and 40% more than the soy group," Phillips says.
Those who drank milk also had more strength gains than the other two groups in two kinds of individual exercises: knee extensions and hamstring curls.
The milk drinkers also lost more body fat. "They lost almost 2 pounds of body fat," he says. "The soy group barely changed in terms of body fat. It was about a third of a pound. In the control group (the carbohydrate drinkers) it was about a pound of body fat lost."
Milk Protein for Muscle Building?
Exactly why the milk group did better is unknown, Phillips says. He speculates that the proteins in the milk -- whey and caseins -- may account for the better results.
"The calcium may allow your body to burn more fat," he speculates.
While the study included only men, Phillips also speculates the results would apply to women.
The weight-trainers in the study were novices, so he says the results for veteran weight-trainers who drink milk after working out may be less.
And yogurt or cottage cheese could possibly work as well as milk, he says.
The carbohydrate drink used in the study wasn't the same composition as Gatorade, says Jeff Zachwieja, PhD, principal scientist at the Gatorade Sports Science Institute in Barrington, Ill.
The study's carbohydrate drink was 9% maltodextrin. Gatorade is 6% carbohydrate with a blend of glucose, sucrose, and fructose as well as the electrolytes sodium, potassium, and chloride to restore minerals lost through sweating, he says.
"They were trying to compare the protein in soy to the protein in milk," he says. The carbohydrate drink served only as the control, to give the researchers something to compare results to.
Gatorade Thirst Quencher's purpose is not to build muscle, Zachwieja tells WebMD. "When you weight train, Gatorade is for replacing the fluid you are losing through sweating and providing some carbohydrate energy during the exercise."
He notes that other Gatorade products -- such as the nutrition shake with protein -- are meant to supply protein after weight training. "We definitely recognize the importance of protein in recovery scenarios," he says. "Protein helps the muscle to rebuild itself."
GeniSoy Food Company in Tulsa, Okla., which makes the soy drink used in the research, had no immediate comment on the study results.
But spokesman Jordan Gilsleider notes that the company web site has a protein calculator to help exercisers calculate how much protein to eat, based on their exercise goals and weight.
An Exercise Physiologist's View
For building more muscle, "milk may be worth a try," says Richard Cotton, a spokesman for the American Council on Exercise in San Diego, and chief exercise physiologist for myexerciseplan.com. He is familiar with the study but not involved in it.
"There may be something about the type of protein in milk vs. soy," Cotton says. He advises people to pay attention to overall protein intake.
But he doesn't think it's crucial to eat protein immediately after a workout. He advises drinking plenty of water to replace fluids immediately after exercise. "But if you are craving protein after a workout, go for it," he says.