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mucus causing foods

Avoiding mucus forming foods is trendy, but should you cut out dairy and foods associated with increasing mucus? Do dairy products, and other foods pigeonholed as mucus forming, actually cause increased mucus production? Does too much mucus cause disease?

The Difference Between Mucus and Phlegm

Mucus (or mucous) is a slippery wet secretion produced by specialized membranes mainly in the respiratory and gastrointestinal tracts. Mucus is made up of glycoproteins and water. It also contains antiseptic enzymes, immunoglobulins, inorganic salts, proteins, and mucins.

The body makes mucus to protect cells that line the respiratory, gastrointestinal, urogenital, visual, and auditory systems. Mucus has an essential function, which is to protect the body from being invaded by fungi, bacteria, or viruses. The human nose produces about a liter of mucus per day .

Phlegm refers to the thicker mucus associated with inflammation in the nasal passages, throat, and lungs. Allergens and air pollutants cause irritation of the mucosal lining of the respiratory tract resulting in increased mucus production and expectoration of phlegm.

Respiratory infections can cause a lot of phlegm. When severe, like in the SARS epidemic of 2002, the body overproduces mucus in an attempt to rapidly shed viruses in phlegm. But, excess mucus may cause the patient to drown in their secretions. It’s important to note that SARS peaked in Hong Kong and China, both countries where adults almost never consume dairy products of any type.

Origin of the Mucus-Milk Myth

Ancient Greek physicians, as well as Arabic, Ayurvedic, and Chinese medicine taught that too much phlegm was a sign of illness. In Traditional Chinese Medicine (TCM), accumulated phlegm is thought to cause tumor s, swollen painful joints, cysts, nodules, and lymph node enlargement.

American natural health gurus of the 1950s through 1980s shared common principles as truths. These included iridology – reading a person’s iris to detect disease in the body – periodic fasting, fresh juicing, liver detoxification, flushing stones from the gallbladder, a vegetarian diet, eating coarse whole grain bread, avoiding processed foods, colon cleansing, and the idea that excess mucus product was at the root of all disease.

The herbalist and natural healer, John Christopher advocated a healthy plant-based diet free of meat and processed foods. He developed the low-mucus diet and coined the term ” mucusless.”

Mucus-Forming Foods According to Dr. Christopher:

  • Dairy products
  • White sugar
  • All meats
  • Wheat flour products
  • Salt
  • Eggs

The Evidence on Mucus-Forming Foods

In the 1990s, a cluster of studies tried to tease out the truth from myth. In one Australian study, even eleven glasses of milk per day didn’t increase mucus production. However, more allergic reactions like coughing occurred. A 2005 study reviewed several milk-mucus studies and found no connection to increased phlegm.

It appears that there is little evidence that drinking cow’s milk or eating cheese increases mucus production. It’s true that people with allergy to dairy products are more likely to have asthma with increased phlegm. But, it’s the proteins in milk that cause allergic reactions; not an increase in phlegm. However, even that notion is questioned by medical experts. The Canadian Family Physician recommends to not withhold milk from children who have asthma or catch a cold.

The Paradox of Casomorphins: The Real Milk-Mucus Link?

The milk-mucus link may be more complicated than these studies discovered. It seems that some people are sensitive to protein fragments called casomorphins derived from milk digestion in the gut.

In particular, beta-casomorphin-7 (BCM7) is associated with increased histamine production, which results in asthma. This BCM7-sensitive group of people also produce more phlegm. Avoiding dairy products reduces their symptoms of asthma. For these people, a dairy elimination diet makes sense.

BCM7 is linked to diabetes, joint pain, depression, sleep apnea in infants, and autism. For BCM7-sensitive infants, it appears that drinking cow’s milk may impair early childhood development. However, the research on the link between autism and casomorphins is limited with nothing appearing in the scientific literature since 2014.

However, newer studies suggest that casomorphins promote maternal bonding, gastrointestinal function, mucosal development, and restful sleep. It appears that human mother’s milk has a soothing opioid effect.

Casomorphins in cheese also produce an opioid effect. This may explain the pleasurable effect of eating cheese, preferably with a nice French wine.

Researchers also found that BCM7 does increase mucin production in the gastrointestinal tract, which is not necessarily harmful. Improved mucosal immunity in the gastrointestinal system helps reduce inflammation. But too much BCM7 increases inflammation markers like myeloperoxidase (MPO).

Muscusless: Dangerous Myth or Important Wellness Choice?

It’s true that withholding milk from young children with the notion that it causes increased mucus production may result in permanent harm. Body strength and height to a large part depend on healthy bones that need calcium. Traditionally, humans breastfed infants and young children for many years. Modern women nurse for a much shorter time. But young children need enough calcium for bone health and growth.

Mother’s milk also contains immune-enhancing substances and supports healthy gut probiotic ecology. Cow’s milk contains calcium and phosphorous for bone growth. However, it also contains substances like lactose, casein, and BCM7 that are known to cause harm.

In my clinical practice, I recommend avoiding dairy products, including for children, when there is confirmed or suspected milk allergy or lactose intolerance. Sheep and goat’s milk do not contain BCM7. Substituting with goat milk is a better choice. Calcium supplementation is advised if you, or your children, avoid all milk.

Dr. J. E. Williams


Dr. Williams is a pioneer in integrative and functional medicine, the author of six books, and a practicing clinician with over 100,000 patient visits. His areas of interest include longevity and viral immunity. Formerly from San Diego, he now resides in Sarasota, Florida and practices at the Florida Integrative Medical Center. He teaches at NOVA Southeastern University and Emperor’s College of Oriental Medicine.

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  1. June Hanson says:

    Happy to hear BCM7 is not in sheep and goats products. Love dairy products, but they do not like me. Your right, eat one piece of cheese, can’t stop, feel so great. Find that adding small amounts of goats and sheep cheese. adds so much flavor to bland food. My problem is not going overboard, then I, notice the difference in how my body reacts.

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