Elsevier

Medical Hypotheses

Volume 74, Issue 4, April 2010, Pages 732-734
Medical Hypotheses

Does milk increase mucus production?

https://doi.org/10.1016/j.mehy.2009.10.044Get rights and content

Summary

Excessive milk consumption has a long association with increased respiratory tract mucus production and asthma. Such an association cannot be explained using a conventional allergic paradigm and there is limited medical evidence showing causality. In the human colon, β-casomorphin-7 (β-CM-7), an exorphin derived from the breakdown of A1 milk, stimulates mucus production from gut MUC5AC glands. In the presence of inflammation similar mucus overproduction from respiratory tract MUC5AC glands characterises many respiratory tract diseases. β-CM-7 from the blood stream could stimulate the production and secretion of mucus production from these respiratory glands. Such a hypothesis could be tested in vitro using quantitative RT-PCR to show that the addition of β-CM-7 into an incubation medium of respiratory goblet cells elicits an increase in MUC5AC mRNA and by identifying β-CM-7 in the blood of asthmatic patients. This association may not necessarily be simply cause and effect as the person has to be consuming A1 milk, β-CM-7 must pass into the systemic circulation and the tissues have to be actively inflamed. These prerequisites could explain why only a subgroup of the population, who have increased respiratory tract mucus production, find that many of their symptoms, including asthma, improve on a dairy elimination diet.

Introduction

Excessive milk consumption has a long association with increased respiratory tract mucus production and asthma. However while large proportions of the population believe this [1], [2], [3], the published medical evidence documenting these links is limited. People who believe that milk increases mucus production have more respiratory tract symptoms, consume less milk and complain that milk increases throat secretions [1]. Such an association cannot be explained using a conventional allergic paradigm.

Section snippets

‘Conventional’ food allergy mechanisms

Immunologically, allergy is subdivided into four classes. The best known, where there is little dispute is the Type I, or immediate hypersensitivity, reaction due to the presence of IgE antibodies against the offending food. Most of the controversy in food allergy relates to Type III allergic reactions involving food IgG immune complexes. T-cell mediated reactions can also be involved. Cases of asthma-like symptoms resulting from consumption of, or exposure, to dairy foods have only

Milk challenge and asthma

Although several studies have examined the effect of dairy exposure on bronchoconstriction, none have shown any major effect. For instance, Woods et al. found no bronchoconstrictive effects when subjects were exposed to 300 ml of UHT milk compared to a rice milk placebo [4]. Haas et al. exposed patients with asthma or healthy controls to whole milk, skim milk, or water. No differences in expiratory flows were found. However, diffusing capacity did decrease after ingestion of whole milk, but not

Milk exclusion and asthma

In contrast, a number of studies have suggested that the exclusion of milk products from the diet may improve asthma symptoms. In the 1950s, Rowe and Rowe suggested that a variety of foods could contribute to asthma and found that in asthma patients, symptoms often improved on an exclusion diet [7], [8]. With the development of effective medications for asthma treatment these observations were neglected.

Pinnock et al. found that when milk was excluded from the diet, symptoms of cough and nasal

Stimulation of mucus production

The two main mucins produced in the respiratory tract are MUC5AC and MUC5B. In airway tissues from healthy individuals, goblet cells typically express MUC5AC, while glandular mucosal cells typically express MUC5B. MUC5AC and MUC5B are present at lower levels in mucus from normal airways than in sputum from patients with asthma, bronchitis or cystic fibrosis [13]. Similar observations have been made in chronic rhinosinusitis and nasal polyposis [14]. Mucus overproduction is now recognized as a

Proposed mechanism of respiratory tract cells exposure to milk protein

The evidence suggests that some food derivatives can pass into the systemic circulation. In healthy individuals, despite high stomach acidity and enzyme activity in the small intestine, 2% of ingested food is absorbed through the intestines in a form that is sufficiently immunologically intact to produce food allergy [20]. In a variety of situations such as during trauma, larger macromolecules have been shown to enter the portal circulation. Stress and the subsequent release of corticotrophin

Hypothesis

The hypothesis is that A1 milk increases mucus production in the respiratory tract in a sub-population of people who have increased intestinal permeability. Specifically, β-CM-7, acts via μ-opioid receptors on goblet cells, to upregulate MUC5AC gene expression and increases mucus secretion. This would occur only in specifically primed tissues and only when β-CM-7 was able to pass into the systemic circulation.

Evaluation of the hypothesis

Using nasal brushings of normal and asthmatic patients, μ-opioid receptors expression would be examined using western blotting and dual immunofluorescence labelling [19]. To establish whether β-CM-7 modulates mucin production in human respiratory tract mucosa – a respiratory tract mucin secreting goblet cell line would be obtained. β-CM-7 would be added to goblet cell cultures at a range on concentrations. MUC5AC mRNA expression would be assessed at several different time points following

Consequences of the hypothesis

The belief that excessive milk consumption causes excessive mucus production is common, however such an association cannot be explained using a conventional allergic paradigm. Mucus overproduction from MUC5AC glands is characteristic of many respiratory tract diseases [15]. β-CM-7 from A1 milk could potentially increase mucus production from these glands.

This association many not necessarily be simply cause and effect. For this to occur there needs to be a number of prerequisites. The person

Conflict of interest statement

None declared.

References (25)

  • A.H. Rowe et al.

    Allergic bronchial asthma. The importance of studies for sensitivity to foods

    Calif Med

    (1956)
  • C.B. Pinnock et al.

    Cross over trial of a high milk diet in asthmatic children

    Proc Nutr Soc Aust

    (1989)
  • Cited by (25)

    • β-Casomorphin: A complete health perspective

      2021, Food Chemistry
      Citation Excerpt :

      Given the fact that BCM modulates cellular metabolism, the influence on allergy signaling was also surveyed. Consumption of milk that can release BCM upon digestion was found to stimulate mucus production from gut MUC5AC glands (Bartley & McGlashan, 2010). In another study, using a human breast-milk sample on the IL-8 secretion in Caco-2 cells demonstrated a three-fold increase in IL-8 secretion in reported allergy milk hydrolysate.

    • The Allergic Patient

      2018, Integrative Medicine: Fourth Edition
    • Integrative Medicine for Respiratory Conditions: Asthma and Chronic Obstructive Pulmonary Disease

      2017, Medical Clinics of North America
      Citation Excerpt :

      Certain types of milk (from specific breeds of cow) contain a protein called β-CM-7, which has been shown to stimulate MUC5AC production. It has been hypothesized that milk ingestion may lead to stimulation of respiratory mucin production in the airway and thus increase phlegm production.14 A brief trial (4–6 weeks) of dairy avoidance may be helpful to discern such an association in selected individuals.

    • The current evidence of integrative approaches to pediatric asthma

      2016, Current Problems in Pediatric and Adolescent Health Care
      Citation Excerpt :

      Dairy is commonly reduced or eliminated because it is believed that milk increases the production of mucous. Although one study showed improvement in respiratory tract mucus production with milk avoidance, another study showed that dairy and egg consumption may actually decrease wheezing.7,12 Overall, there is insufficient evidence to restrict milk in asthmatic children.13

    • Dairy Recommendations for Ill Pediatric Patients

      2014, Journal of Pediatric Nursing
    • The Allergic Patient

      2012, Integrative Medicine, Third Edition
    View all citing articles on Scopus
    View full text