Milk may be known for building bones, but new research suggests it's important in boosting muscle mass as well.

Researchers found that young men who followed their weight training regimens with a couple glasses of skim milk gained extra muscle mass. Compared with their counterparts who consumed soy or carbohydrate drinks, the milk drinkers gained up to 60 percent more muscle mass, on average.

They also lost substantially more body fat over the 12-week exercise period.

The study, which is published in the American Journal of Clinical Nutrition, received funding from the National Dairy Council.

Weightlifters have long turned to protein supplements such as whey to help them build muscle. Milk provides not only whey, but other proteins as well.

According to Dr. Stuart M. Phillips, the senior author on the new study, milk proteins contain amino acids -- the building blocks of proteins -- in quantities and ratios that may be more effective than soy protein in building muscle.

Milk proteins are also digested differently from soy proteins, explained Phillips, an associate professor at McMaster University in Ontario, Canada.

In theory, he told Reuters Health, this difference may help muscle retain more of the amino acids from milk.

For their study, Phillips and his colleagues recruited 56 men between the ages of 18 and 30 and put them on a strength training regimen. All of the men worked out five days a week for 12 weeks.

One-third followed their workouts with two glasses of skim milk, one immediately afterward and the second an hour later. Another third drank a fat-free soy beverage, and the rest consumed a high-carbohydrate sports drink. All of the beverages had the same number of calories.

In the end, all of the men increased their muscle mass, but the gains were greatest in the milk group, the researchers found.

When it came to body fat, the losses were greatest in the milk group. On average, milk drinkers lost 5.5 percent of their original fat mass, versus only 1.5 percent in the soy group and 3.4 percent in the carbohydrate group.

There were no clear differences in muscle strength among the three groups.

However, Phillips said, gains in muscle mass -- and dips in body fat -- are beneficial regardless of the effects on strength.

He likened larger muscle mass to having a "bigger furnace" in the body; muscle increases metabolism and acts as a "disposal site" for blood sugar and fats. This means that building muscle could potentially protect against health problems like obesity, type 2 diabetes and high cholesterol, Phillips said.