You've probably heard the age-old advice to avoid dairy milk when you're congested. This advice might have come from your mother, a well-meaning friend or the family physician. The widely held notion that milk stimulates mucus production may pass for conventional wisdom, but evidence suggests that it isn’t entirely accurate.
Milk has not been shown to increase the amount of mucus the respiratory system produces. A 2005 article published in the “Journal of the American College of Nutrition” reported no measurable difference in the nasal secretions of milk drinkers, even though individuals who said they believed that milk stimulates mucus production did claim to feel more congested after drinking the beverage.
Milk is a relatively dense liquid that coats your throat as it goes down. It also makes mucus somewhat thicker and more difficult to swallow, according to the Australasian Society of Clinical Immunology and Allergy. This may account for the reason why some people associate milk with increased amounts of phlegm.
Milk does stimulate the production of mucus in your intestinal tract as it becomes digested. Because mucus originates in your gut, however, this mucus doesn’t generally cause congestion or other respiratory symptoms. If you experience thicker mucus after consuming milk, drinking water can help thin it out.