When a runny nose or congestion appears, many people believe they need to cut out milk to reduce mucus. It turns out that this is a myth, and studies show that milk does not cause mucus. Researchers think the false belief may come from how milk feels in the mouth and throat because of its naturally creamy texture.
What does the science show?
A review of the scientific evidence published in the journal of Archives of Disease in Childhood by the Department of Paediatric Respiratory Medicine, Royal Brompton Hospital, London, UK shows no increase in mucus production from milk.1 In fact the review referred to milk as “an important source of energy, and the principal source of calcium for children and adults, as well as a good source of several vitamins.”
The review explains that getting enough calcium is critical for normal bone health and for preventing osteoporosis. The author concludes that “the milk–mucus myth needs to be rebutted firmly by healthcare workers.”
In the 1990s, two studies were carried out to examine the milk and mucus link. A study published in 1990 focused on 60 adults with sinus colds. Researchers collected data on symptoms, milk intake and mucus, and found no correlation between milk or dairy intake and symptoms of congestion or the weight of nasal secretions produced.2
In 1993, a study divided subjects into a milk or placebo (soy beverage) group.3 Both groups reported that drinking milk or soy beverage caused:
• Coating over the mouth
• Coating over the back of the throat
• The need to swallow
• Thick saliva
This study shows that both beverages caused the symptoms, and the belief may be related to the texture of these beverages, but not specifically to milk. The naturally creamy texture of milk will coat the mouth. Milk mixed with saliva may feel thick, but it does NOT mean more mucus is produced. There remains no clinical evidence that milk leads to excessive mucus production or secretion.
Interestingly, in this study, people who believed that milk caused mucus (before the test) were more likely to report effects like a thick mouth coating.4 Bottom line: there was a thick feeling from milk, but it didn’t actually cause more mucus production.
Dispelling a myth
Health professionals can play an important role in dispelling this nutrition myth. The false belief that milk increases mucus is not based on evidence. Armed with the facts, you can assure patients that milk does not cause mucus and avoiding milk is not recommended.
Patient context: Origins of a myth
Beginning in 1946, millions of bookshelves in family homes across North America featured Dr. Spock’s parenting manual Baby and Child Care. Within the pages, Dr. Spock wrote that “dairy products may cause more mucus complications and more discomfort with upper respiratory infections…” and parents believed it to be a fact. Truth is, this fallacy was based on opinion, not science.5
In 1948, doctors tested Spock’s theory. They conducted a study where they carried out nose and throat exams on 157 people. The finding? There was no excess mucus noted in those who drank milk versus those who did not. Yet the myth remained in print, showing that even in the 1940s, influencers with a large following are trusted more than science. In fact, this milk and mucus advice remains in the 9th edition of Dr. Spock’s book, even though it’s simply not true.