Old Wives Tale or Real Problem? Milk and Mucus Secretion

The 12th-century Jewish physician Maimonides is perhaps best remembered for his advice to enjoy a bowl of chicken soup to fight off a cold. Modern science supports his idea. Chicken soup has anti-inflammatory and other symptom-easing properties.

But he also made another statement that's been passed down through the generations. He said milk causes "a stuffing in the head."

Although not as famous as the chicken soup remedy, apparently word got around. I’ve met any number of people who think milk makes their sinus problems worse.

Most scientists didn’t buy into it -- until now. A new study suggests milk does increase mucus production, make cold symptoms worse, and should be avoided by those with respiratory infections.

Let’s take a look. . .

Skeptical Doctor Surprised

The randomized, double-blind study published in the journal Laryngoscope in September was carried out by Adam Frosh and colleagues at the Department of Ear, Nose and Throat Surgery, Lister Hospital, Stevenage, England.

Dr. Frosh explains his reason for exploring the milk-mucus link like this: "I was skeptical and didn’t believe it was real [but] I have been asked about it by so many patients over the years that I felt I needed to look into it — if only to put the idea to rest."

So the research team recruited 26 men and 82 women who suffered with persistent increased mucus secretions in the head and upper body.

All were put on a dairy-free diet for six days. On days three to six, half drank 12 ounces of full-fat cow's milk while the other half drank the same amount of soya milk. Both drinks were flavored so they tasted exactly the same.

Everyone self-reported less mucus in the first two days. But over the next four days the soya group experienced a continuing reduction in symptoms, while a significant increase in mucus was described by the cow's milk group.

Commenting on the findings, Dr. Frosh said, "The results were the opposite of what I was expecting. This was quite a big effect in a relatively short space of time. It’s reasonable to conclude that anyone who feels milk increases their mucus production should consider reducing their dairy intake, or try a dairy-free diet, to see if it improves their symptoms."

It's All a Myth

One doctor who remains unconvinced is children's respiratory consultant Ian Balfour-Lynn from Royal Brompton Hospital, London.

He carried out an extensive review of existing research that was published in Archives of Disease in Childhood in the same month as the Lister Hospital study. He wrote, "[T]here is no evidence...that milk leads to excessive mucus secretion...The milk–mucus myth needs to be rebutted firmly.”

Dr. Balfour-Lynn believes the texture of milk -- an emulsion of fat in water -- makes people feel their saliva is thicker and harder to swallow, and it leaves an after-feel because small amounts remain in the mouth. This gives the impression of greater mucus.

So is the effect real, as supported by Dr. Frosh's study, or imaginary, which is Dr. Balfour-Lynn's strong view? Perhaps the answer lies elsewhere.

Not all Milk is The Same

The milk almost everyone drinks is A1, derived from Holsteins and Friesian breeds. An opioid derived from the breakdown of A1, called BCM-7, should stimulate mucus production in the gut, but not elsewhere in the body.

However, BCM-7 may also create mucus in the respiratory system if two conditions are present at the same time. First, if the gut is leaky, allowing BCM-7 to be absorbed into the bloodstream, and second, if inflammation is already present in the respiratory organs.

So the observation dating from the Middle Ages is at least partly correct. Milk will create mucus and worsen symptoms in some people with colds, but it depends on the gut and respiratory health of the individual and type of milk consumed.

Those who want to drink milk without BCM-7 can do so by buying sheep and goat milk. Alternatively, it may be possible to find A2 milk from older breeds of cow. Here, BCM-7 remains tightly bound, preventing its release in the gut.