Skim milk best for pumping up muscle mass

NEW YORK (Reuters Health) - Weightlifters who drink skim milk after a workout will build about twice as much muscle as those who rely on soy beverages, a new study suggests.

What’s more, milk is far cheaper than supplements specifically designed to help weightlifters pump up after a workout, Dr. Stuart M. Phillips of McMaster University in Hamilton, Ontario, the study’s lead author, told Reuters Health. The researchers used powdered skim milk in the current study, available in any grocery store.

“I have done these calculations and figure that ounce for ounce milk is 20-30 times less expensive than most supplemental protein sources available,” he said in an e-mail interview.

Consuming protein after “pumping iron” is known to help build muscle mass, Phillips and his team note in the American Journal of Clinical Nutrition, but it is not clear whether some types of protein are more effective than others.

Quickly digested or “fast” proteins, including whey and soy, cause a temporary flood of amino acids into the blood, they explain, making more of these protein “building blocks” available for uptake by muscle. Proteins that take longer to digest, such as casein that is found in milk, produce a more gradual and long-lasting increase in blood levels of amino acids. While these “slow” proteins don’t promote muscle formation, they do prevent muscle breakdown.

The researchers hypothesized that a combination of “slow” and “fast” proteins like casein and whey, both found in cow’s milk, would be most effective for building muscle. To investigate, eight men who regularly lifted weights were given a soy beverage or skim milk after performing a series of exercises with one leg.

For three hours after the workout, the researchers found, muscle uptake of amino acids was significantly greater when the men drank milk than when they consumed soy.

The gains were measured in this study after a single workout, “but if extended out to 10 weeks the data suggest (but did not show) that gains in muscle mass would be twice as great with milk as with soy,” Phillips said.

In other research, Phillips and his colleagues found evidence that milk may also benefit athletes after exhaustive exercise, such as cycling.

The current study was funded by the National Dairy Council, along with the Canadian Institutes for Health Research. However, Phillips noted, the council had no say in the study’s publication and did not vet the manuscript.

SOURCE: American Journal of Clinical Nutrition, April 2007.