Dangers of Dairy – Casein Sensitivity

Mindd Foundation

Have you heard of Casein Sensitivity? Casein is the major protein found in cow’s milk, and for some, it is a problem.

Dairy consumption worldwide is astoundingly high. It is estimated that between 94-99% of people regularly consume dairy products1 and up to 36% of people drink 2-3 glasses of milk a day2. Dairy is often recommended as highly nutritious and beneficial.

However, there is a negative side to dairy and it has been linked to several conditions. Lactose intolerance is known to give gastrointestinal symptoms such as bloating, gas, diarrhea and abdominal discomfort. These gastrointestinal issues are down to the lack of an enzyme that breaks down lactose, the milk sugar.

Protein in dairy may also pose problems and cows’ milk allergy, delayed or immediate, may affect many children between the ages of one and five. Casein Sensitivity, often not involving IgE antibodies, is also more common than first thought.

Dairy Proteins and Casein Sensitivity

Cows’ milk contains two main types of protein – whey and casein. Over 80% of the total protein in milk is in the form of casein.

Some dairy products, such as cheese, have higher levels of casein compared to milk. Casein may be in different forms in milk and beta-casein is the second most common form.

Beta-casein itself has many variants and among the most common are the A1 beta-casein and A2 beta-casein variants. The amount of each variant present depends on the breed of cow. Some cows such as Red, Holstein-Friesian and Ayrshire produce high levels of the A1 variant of beta-casein, whereas Guernsey and Jersey cattle produce the A2 variant of beta-casein3.

Why is the Type of Casein so Important?

The A1 variant of beta-casein has been shown to be digested and release the bioactive peptide beta-casomorphin 7 (BCM-7)4.  Casomorphins act like opiates in the body and can target opiate receptors in the brain. Some people feel “addicted” to dairy because of casomorphins. Casomorphins have also been shown to directly raise histamine5, which is involved in the inflammatory response to allergens.

How can Dairy be such a Danger?

The A1 variant of beta-casein has been shown to be involved in several conditions and has been linked to:

  • Increased mucus production associated with respiratory conditions such as asthma6
  • Increased risk of developing insulin-dependent diabetes7
  • Oxidative damage of LDL cholesterol, which is a factor in the development of arterial plaques8
  • Coronary heart disease9
  • Increase in sleep apnea 10and link to Sudden Infant Death Syndrome11
  • Autism Spectrum Disorders12,13

Immune Involvement in Casein Sensitivity

Production of IgG and IgA antibodies in response to casein may be seen in those with casein sensitivity, although it has also been identified that these antibodies may be seen even in those not sensitive, or allergic, to cows’ milk14. Some studies have suggested that testing for IgG or IgA casein antibodies cannot be accurately used for a diagnosis of cows’ milk protein intolerance15.

High levels of both these antibodies have been shown in cases of ASD, schizophrenia16 and dyslexia17. Casein has also been shown to influence the release of inflammatory cytokines18 (chemical messengers) in autism which can affect the gut lining19 and lead to further problems with food sensitivities.


As testing for the presence of IgA and IgG antibodies to casein may not give a firm diagnosis, there may be an alternative. Urine levels of casomorphin peptides can be assessed and may give an indication that there is an issue with casein. Elevated urine levels of casomorphin peptides have been seen in those with ASD, schizophrenia and celiac disease20.

Casein sensitivity symptoms

Casein is slowly digested and may put a strain on the digestive system. It may take time for symptoms to appear 21 and the degree of the symptoms may be linked to the amount of casein ingested. So, a repeated high volume of casein ingestion may give rise to more obvious, troubling symptoms. The symptoms themselves can be diverse and range from diarrhea, constipation, bloating, cramps, skin rashes, joint discomfort and fatigue through to behavioral alterations.


Key points:

  • Cows’ milk has two main types of protein – whey and casein.
  • Casein itself has many variants and the two most common are A1 beta-casein and A2 beta-casein
  • A1 beta-casein can be broken down to release a bioactive peptide called Beta-casomorphin-7 (BCM-7)
  • BCM-7 is linked to mucus production, asthma, diabetes, heart disease, sleep apnea and SIDS, ASD
  • Casomorphins have opioid-like activity and may target the brain, they also directly raise histamine and influence the release of inflammatory cytokines
  • Casomorphin peptides may be tested in urine and elevated levels have been seen in ASD, schizophrenia and celiac disease
  • Symptoms of casein sensitivity may vary and be delayed for several weeks

Casein Sensitivity may not be the only sensitivity to consider, so it is important to look further for problem foods. In particular Gluten, Corn and Soy as well as lectin sensitivities caused by foods from the Nightshade Family (e.g. tomatoes, potatoes).


  1. http://www.dairyuk.org/industry-overview/consumption-sales Accessed 24.11.16
  2. http://www.statisticbrain.com/milk-consumption-statistics/ Accessed 24.11.16
  3. Kamiński, S., Cieślińska, A., & Kostyra, E. (2007). Polymorphism of bovine beta-casein and its potential effect on human health. Journal of applied genetics, 48(3), 189-198.
  4. Boutrou, R., Gaudichon, C., Dupont, D., Jardin, J., Airinei, G., Marsset-Baglieri, A., … & Leonil, J. (2013). Sequential release of milk protein–derived bioactive peptides in the jejunum in healthy humans. The American journal of clinical nutrition, 97(6), 1314-1323.
  5. Kurek, M., Przybilla, B., Hermann, K., & Ring, I. (1992). A naturally occurring opioid peptide from cow’s milk, beta-casomorphine-7, is a direct histamine releaser in man. International archives of allergy and immunology, 97(2), 115-120.
  6. Bartley, J., & McGlashan, S. R. (2010). Does milk increase mucus production?. Medical hypotheses, 74(4), 732-734.
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  2. Sodhi, M., Mukesh, M., Kataria, R. S., Mishra, B. P., & Joshii, B. K. (2012). Milk proteins and human health: A1/A2 milk hypothesis. Indian J Endocrinol Metab, 16(5), 856.
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  8. Hidvegi, E., Cserhati, E., Kereki, E., Savilahti, E., & Arato, A. (2002). Serum immunoglobulin E, IgA, and IgG antibodies to different cow’s milk proteins in children with cow’s milk allergy: association with prognosis and clinical manifestations. Pediatric allergy and immunology, 13(4), 255-261.
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  14. https://www.greatplainslaboratory.com/glutencasein-peptides-test Accessed 24.11.16.
  15. Montalto, G., Custro, N., Notarbartlo, A., Carroccio, A., Cavataio, F., D’amico, D., … & Iacono, G. (2000). Evidence of very delayed clinical reactions to cow’s milk in cow’s milk‐intolerant patients. Allergy, 55(6), 574-579.

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