Writing in the journal Medicine and Science in Sports and Exercise, researchers at McMasters University in Canada investigated the impact on lean muscle mass gain and fat loss among female resistance athletes of drinking a sports beverage and a skimmed milk drink.
The scientists wanted to find out whether milk offered the same benefits to female athletes as it does to male ones.
To establish this they gave either fat-free skimmed milk or a carbohydrate drink to women immediately after resistance training and then again an hour later. The women exercised five days a week for 12 weeks and changes in their body composition were measured.
The results showed that muscle mass increased in both those drinking milk and the carbohydrate drink but women drinking milk gained more muscle mass. In addition, milk drinkers were the only ones to experience a reduction in fat mass after training.
Milk mechanisms
Explaining the results, lead author Andrea Josse, said: “We believe there are 2 main constituents (among many other minor ones) in milk that are responsible for its beneficial effects on muscle gain and fat loss: the protein and the Calcium/vitamin D.”
Regarding muscle gain, Josse told DairyReporter.com that milk contains amino acid building blocks that help trigger muscle growth, but are typically absent in carbohydrate drinks.
Josse highlighted the importance of Leucine, an essential amino acid found in significant quantities in dairy protein that has been shown to trigger protein synthesis at a molecular level.
With respect to fat loss, Josse said: “There have been many studies done in cells and animals and a few clinical trials done in humans highlighting the relationship between vitamin D, calcium and fat loss. The mechanisms are pretty complex involving many hormones and enzymes but it boils down to the more calcium you have in your blood (and in our case we increased this by consuming milk), the greater fat loss.
A sports drink may contain a little calcium, but the levels typically found are low compared to those in a milk drink. The sports drink used in the McMasters study contained no calcium.
The gender question
The results of the study tally with those found when studying men. A McMasters study published in the American Journal of Clinical Nutrition in 2007 examined the effects of milk consumption on muscle gain and fat loss in male resistance athletes.
Josse said that comparing the two studies no differences were seen between men and women with respect to body composition changes. According to the Dairy Council, this indicates that milk is an effective drink to support favourable body composition changes in women who do resistance training.
“Many studies regarding sports nutrition are conducted in men and this shows how the same benefits of consuming milk can be applied to women,” said Judith Bryans, director of The Dairy Council.
The funding for the study came from the Natural Sciences and Engineering Research Council (NSERC) of Canada, the Canadian Institutes of Health Research (CIHR) and the Dairy Farmers of Canada. The study has been published online ahead of publication.
Source: Medicine and Science in Sports and Exercise
doi: 10.1249/MSS.0b013e3181c854f6
Body Composition and Strength Changes in Women with Milk and Resistance Exercise
Authors: Josse, Andrea R.; Tang, Jason E.; Tarnopolsky, Mark A.; Phillips, Stuart M.