A review of the scientific evidence by Zaitlin et al,1 concluded that there is no increase in mucus production based on the studies that have been done. People who believe in the “milk-mucus connection” may perceive the sensation of having more mucus but this may be due to the milk and saliva mixture itself, or a placebo effect.1 Drinking milk sometimes leads to sensations of ‘‘coating of the throat’’ or ‘‘thicker saliva,’’ but these are sensations that are due to the viscosity and velvety texture of milk rather than an increased production of mucus.
In practice
The belief that milk increases mucus production is not supported by scientific evidence. Rather, it is hypothesized that this impression is due to the creamy texture of milk, which coats the mouth and causes a “thickened” sensation.
Another review echoed similar conclusions especially as related to children. The author concludes that “Milk is an important source of calories, calcium and vitamins for children. The milk–mucus myth needs to be rebutted firmly by healthcare workers.”2
In one study, 60 healthy adults were challenged with a common cold virus (rhinovirus 2) and their symptoms and milk intake were recorded. Milk was not associated with an increase in symptoms.3 Similarly, other studies have shown that drinking cow’s milk does not cause the production of mucus or increase symptoms of cough or congestion.4
Although research has not shown a link between milk consumption and increased mucus secretion, a few studies have shown an association between the belief in this myth and the incidence of reported symptoms. 3,5,6 In a study by Pinnock et al, subjects who believed that milk causes mucus reported symptoms such as difficulty swallowing, thick saliva and congestion. However, although the believers reported more symptoms, they did not actually have higher levels of mucus than people who did not believe the myth.3
Furthermore, a subsequent study by Pinnock and Arney compared cow’s milk with soy beverage, which has similar mouth-feel characteristics, in a double-blind trial. Subjects who believed that milk causes mucus reported similar effects with both beverages,5 indicating that this belief may be related to the texture of the beverage and not specifically to cow’s milk.
The mucus myth likely stems from milk’s creamy texture, which can leave a coating in the mouth and throat but does not cause mucus. This mouth-feel may be reduced by drinking very cold milk or by even adding ice cubes in the glass. The overall research does not support an increase in the production of mucus or other cold-related symptoms as a result of consuming milk.
References
- Zaitlin P et al. Mistaken beliefs and the facts about milk and dairy foods. Nutr Today 2013;48(3):135-143.
- Balfour-Lynn IM. Milk, mucus and myths. Arch Dis Child 2019;104:91–93.
- Pinnock CB et al. Relationship between milk intake and mucus production in adult volunteers challenged with rhinovirus-2. Am Rev Respir Dis 1990;141(2):352-6.
- Wuthrich B et al. Milk consumption does not lead to mucus production or occurrence of asthma. J Am Coll Nutr 2005.24(6 Suppl):547S-55S.
- Pinnock CB and Arney WK. The milk-mucus belief: sensory analysis comparing cow’s milk and a soy placebo. Appetite 1993;20(1): 61-70.
- Arney WK and Pinnock CB. The milk mucus belief: sensations associated with the belief and characteristics of believers. Appetite 1993; 20(1): 53-60.
