Dairy can be as polarising as politics. Some athletes claim cow's milk causes stomach aches, aggravates inflammation and produces phlegm; others tout its benefits.
Milk products contain loads of vitamin D, calcium and high-quality proteins that provide the full spectrum of amino acids necessary for rebuilding muscle cells. In fact, several studies have shown that milk's blend of protein, carbohydrates and electrolytes (such as potassium and magnesium) make it as effective as a sports drink.
"Milk is good for you, but there's a time and place for it," explains Robert Kunz, of endurance-specific sports nutrition company First Endurance. Here, we explain where and when dairy does your body good.
Myth 1: Dairy helps you lose weight
A clinical review published in May 2008 found that among 49 studies examining dairy and body weight, only five produced evidence of weight loss. Most concluded that dairy has no effect, and a few studies resulted in subjects gaining pounds. "Dairy is nutrient-dense," says dietician Cara Marrs. Don't expect to shave pounds with low-fat versions; one cup of two per cent milk contains 138 calories - eight fewer than a cup of whole milk.
Myth 2: Dairy increases mucus production
Several studies, including a 2005 review published in the Journal
of the American College of Nutrition, found no measurable mucus increase among milk drinkers. "Yet I've had cyclists tell me that drinking milk makes them cough stuff up during their ride," says Roberta Anding, a spokesperson for the American Dietetic Association. The culprit could be certain genes that may cause increased mucus production. Anding recommends triathletes perform a self-test: if dairy produces phlegm that clogs your breathing, don't drink any until after your ride.
Myth 3: Dairy triggers inflammation
"There's mixed evidence on whether dairy is pro- or anti-inflammatory," says Anding. One study published in the June 2008 Journal of Nutrition suggests that milk products reduce inflammation, but other trials have documented increases. That's why Kunz recommends that triathletes eliminate dairy for several days before a major endurance event. "It seems to cause inflammation in the gut," he says, which can keep triathletes from efficiently absorbing carbs, electrolytes and other nutrients that are critical for their peak performance.
Myth 4: Dairy is difficult to digest
For some individuals, this is true. "Some people lack lactase, an enzyme that digests lactose, a sugar found in milk," Marrs explains. Genetics, ethnicity and age (over time, some people's lactase levels decline) can influence the ability to produce lactase. But Marrs cautions against eliminating dairy from your diet. "When you cut out entire food groups, you're limiting your nutrition intake," she says. If milk upsets your stomach, try yoghurt or experiment with various cheeses (aged cheeses are lower in lactose). "Try to pinpoint the aggravating foods rather than assuming that all milk products are indigestible," adds Marrs.
Myth 5: Dairy strengthens bones
A 2009 trial published in the Journal of Bone and Mineral Research found that milk-fed rats had stronger, denser bones than those that consumed calcium carbonate (a supplement).