May 08, 2013

Does Milk Cause Increased Phlegm or Mucus Production?

For many individuals, milk and associated dairy products definitely seem to cause an increased production or thickening of mucus in the mouth and throat... the phlegmy throat. It certainly happens to me...

Of course, perception is not always supported by research...
"Milk and dairy product intake was not associated with an increase in upper or lower respiratory tract symptoms of congestion or nasal secretion weight. [...] We conclude that no statistically significant overall association can be detected between milk and dairy product intake and symptoms of mucus production in healthy adults, either asymptomatic or symptomatic, with rhinovirus infection." [link]
However, other research support the possibility that dairy products might increase mucus production only if the milk contains beta-CM-7 protein (not all milk contains this protein). [link]

I have a different hypothesis for why milk may cause the perception of increased mucus production. I should preface that I have no research study to quote to prove this hypothesis. Might be a good research project for a medical student???

In any case, milk contains a protein called casein. When the milk is not refrigerated, it causes bacteria to  metabolize lactose within the milk leading to lactic acid production as a byproduct. When acidity is present, the casein congregate in a process called curdling. That's the "chunks of milk" seen in milk gone bad.

Now, bacteria certainly will not be playing a role in lactic acid production after fresh milk is consumed, BUT, there IS acid present in the stomach which can initiate curdling.

Now what if a patient suffers from acid reflux... and what if some of the reflux episodes reach the throat level?

So, hypothetically speaking, if somebody who suffers from acid reflux drinks a lot of milk, two things might hypothetically happen (or drinks orange juice followed by milk):

1) Milk temperature goes up from body heat (which assists in curdling)
2) Acid present from the reflux will initiate curdling

If acid is present in the mouth and throat from reflux or secondary source (like recently drunk orange juice), curdling to some degree may occur from milk residue mixing with acid residue present leading to perception of mucus production.

Now does this actually happen???

I don't know and I hope some researcher looks into this hypothesis further!

However, in the end, if dairy avoidance helps with a phlegmy throat, than it can't hurt to avoid it! I should also point out that egg and wheat does cause a similar phlegmy problem in some patients.

Relationship between milk intake and mucus production in adult volunteers challenged with rhinovirus-2. Am Rev Respir Dis. 1990 Feb;141(2):352-6.

Does milk increase mucus production? Med Hypotheses. 2010 Apr;74(4):732-4. doi: 10.1016/j.mehy.2009.10.044. Epub 2009 Nov 25.

Fauquier blog
Fauquier ENT

Dr. Christopher Chang is a private practice otolaryngology, head & neck surgeon specializing in the treatment of problems related to the ear, nose, and throat. Located in Warrenton, VA about 45 minutes west of Washington DC, he also provides inhalant allergy testing/treatment, hearing tests, and dispenses hearing aids.


Anonymous said...

When I was pregnant I had a lot of reflux, and milk actually helped calm and reduce the reflux. I drank a lot of milk while I was pregnant due to this! (and TUMS pills) I figured milk has a lot of calcium, like TUMS, so it would help to neutralize the acid. Regardless it did seem to help. Also my mom would always give me ice cream when I was a child, when my throat was hurting.

Anonymous said...

ps, I also find that milk is very soothing to drink just after I throw up. It may be that milk causes increased mucus, but from my experience, I doubt it has to do with curdling. I frequently get excess mucus in my throat but in my case I don't think it has anything to do with milk since I frequently get mucus when I haven't had any milk.

Anonymous said...

I suffer from scud reflux, have done for as long as I can remember and what you describe above is spot on! Feeling sick, curdling, coming back up, and god forbid if you drunk orange juice at the same time!

However i found in pregnancy a little milk did help with heartburn! or a shot of pep, but the best help were lover hearts or refresher sweets!!

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