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It’s a belief almost as old as the product
it’s about.
Back in Egypt in the 12th century, a royal physician
warned that dairy can make you stuffy
in the head.
No one seems to know where he got that idea from,
but it’s become a common belief worldwide
that gulping down a glass of milk or a grilled cheese
will leave you with more mucus than
a tissue can hold.
But... there seems to be no scientific evidence to back up that claim.
The idea that milk worsens congestion is one
of the most prevalent and persistent medical beliefs.
And while it might seem like a silly thing
to worry about, if dairy does increase mucus
secretion in the respiratory tract,
it would not only make colds more annoying—
it could be harmful to people with respiratory conditions
like asthma.
So far, only a few rigorous experimental scientific
studies have tried to determine if the milk-mucus
effect is real, and none have found support for the idea.
Several studies of asthmatics found that lung functioning—
like how much air you can blow
out in one second—
weren’t affected by eating dairy.
And, in a study from the early ’90s,
people who were infected with a common cold virus
didn’t cough, sneeze or make any more nose gunk
if they drank milk.
That doesn’t stop people from feeling like
they’re more phlegmy after a tall glass
of 2%, though.
In a double-blind study published in the journal
Appetite in 1993, 169 participants said drinking
a flavored milk drink left a coating in their mouths,
and that after drinking it, they needed
to swallow more and their saliva was thicker.
The thing is, they said the same thing about
a soy placebo drink which did not contain
dairy.
And neither beverage significantly increased
the severity of mucus-related symptoms like
coughing or sneezing.
That could suggest the nocebo effect is at
play—the phenomenon where expecting something
bad to happen literally makes it happen.
Basically, the awful flipside of the placebo effect.
Or, it could be the fat in milk-like drinks
makes people’s mouths feel a particular
way without actually changing mucus production.
You see milk is an emulsion—
droplets of fat hanging in water—
and saliva makes these
fatty drops clump together.
Globbier fat drops might feel a bit like mucus
or hang around in your mouth for longer,
making you think there’s more mucus when there really isn’t.
Though more research could really nail the coffin
shut on this idea, there’s just no
evidence that dairy products actually cause
you to produce more mucus.
So go ahead!
Drink that milky boba tea, snack on that cheese stick,
whatever you wanna do, unless you’ve got
lactose intolerance or you're vegan or you
just hate cheese...I'm not in charge of your life.
Thanks for watching this episode of SciShow!
If you like learning about milk
and how it affects your body,
we've got more stuff for
you like our episode which explains
how people can drink milk as adults—
something most animals do not do.
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