At the end of nearly every training session, Matt Whitmore downs a pint of milk straight from the bottle.
"I do it pretty religiously," said Whitmore, 25, a gym trainer in London. He first started drinking milk after exercise about 10 years ago when he couldn't afford expensive supplements or protein shakes. "Milk helps me recover faster and I feel great afterwards," he said. "And now, I hate to train without it."
Researchers are giving scientific support to a view that Whitmore vouches for from experience: that milk may be just as good or even better than sports drinks for serious athletes recovering from exercise. The health benefits of milk - which has carbohydrates, electrolytes, calcium and vitamin D - have long been established. But for athletes, milk also contains the two proteins best for rebuilding muscles: casein and whey.
Muscles get damaged after an intense bout of aerobic exercise like running, playing football, or cycling. The casein and whey proteins in milk are precisely what the body needs to regenerate muscles fast.
Glenys Jones, a nutritionist at Britain's Medical Research Council, said milk's protein content makes it an ideal post-exercise drink. "Milk provides the building blocks for what you need to build new muscles," said Jones, who has no ties to the dairy industry.
She said sports drinks mainly replace lost carbohydrates and electrolytes, and don't usually have the necessary nutrients for muscles to regenerate themselves.
Experts have generally been divided over whether milk outperforms sports drinks. Dairy producers have been eager to break into the multibillion-dollar market, often sponsoring research into milk's athletic benefits that some call biased. So the debate continues, but milk has been getting a lot of attention.
In a study published in the journal Applied Physiology, Nutrition and Metabolism in June, researchers found people who drank milk after training were able to exercise longer in their next session than people who had sports drinks or water.
"It's the form of the carbohydrate and the nutrients in milk that is most important," said Emma Cockburn, a lecturer in sports coaching at Northumbria University in northeast England who led the study, which was partially paid for by the dairy industry.
Cockburn advised athletes to drink milk immediately after working out. "The damage caused by exercise leads to a breakdown of the protein structures in your muscles, but that doesn't happen until 24 to 48 hours later," she said. If athletes drink milk right after training, then by the time it is digested, the milk's nutrients are ready to be absorbed by the muscles that have been hurt.
Drinking milk also may help athletes recover quicker if they are performing multiple times in a day. For people who can't stomach the idea of plain milk, experts recommend adding some chocolate or other artificial flavor. At the Beijing Olympics, six-time gold medallist Michael Phelps regularly downed a flavored milk drink in between races.
Scientists at Loughborough University have found low-fat milk is better than sports drinks for replacing fluids lost during exercise. Scientists suspect there may be two reasons for that. Not only does milk have a lot of electrolytes, but it is emptied from the stomach more slowly than sports drinks, keeping the body hydrated for longer.
Though the vitamins and proteins found in milk are present in soy milk or dietary supplements, experts say milk has better proportions of those nutrients.
Milk also may help athletes shed fat and build muscle. In a small Canadian study, experts found women who drank milk after lifting weights gained about 4.4 pounds (2 kilos) of muscle and lost about the same amount of body fat. Women who drank sports drinks put on about 3.3 pounds (1.5 kilos) of muscle but didn't lose any body fat.
"It may be that some of the components of milk - the protein, the vitamin D and the calcium - act in a synergistic fashion to promote fat loss," said Stuart Phillips, a professor of kinesiology at McMaster University who led the research. Phillips has advised the Canadian Olympic Association about milk and the dairy industry paid for part of his research.
But some experts warned that drinking milk after exercise isn't for everyone. Catherine Collins, a spokeswoman for the British Dietetic Association and a dietician at London's St. George's Trust, said while milk may be beneficial for elite athletes who burn thousands of calories a day during their intensive training, occasional gym-goers may be better off drinking sports drinks or plain water.
"If you're just a gym bunny trying to lose a bit of weight, water is probably sufficient after exercise," she said, warning that chocolate milk in particular could add unwanted calories.
At the Vancouver Olympics, dairy farmers trucked in about 85,000 extra quarts (80,000 liters) of chocolate milk. Canadian athletes won a record-setting 14 gold medals. "I don't know if the milk helped, but it can't have hurt," Phillips said.
Still, even those who promote milk as a recovery drink say it cannot entirely replace sports drinks. Because it is harder to digest, people should only drink milk after they are finished exercising, not during.
In comparison, sports drinks like Gatorade have easily digestible sugars so athletes can chug it during events to get an instant boost.
Whitmore says it may be a tough sell to persuade people to swap their sports drinks or even water, for milk. "Most gym goers have very particular routines," he said, acknowledging he takes a bit of ribbing for his milk habit from his rugby teammates. "They call me the Milky Bar kid."