Cow’s milk in particular is one of the most used dairy products globally, with over 800 million tons produced annually according to the United Nations Food and Agriculture Organization1. Recently, a new type of cow’s milk has appeared in the dairy aisles. This product, called A2 milk, has garnered attention from both consumers and scientists.
Differences between A1 and A2 milk
Approximately 30% of cows’ milk protein is β-casein, of which two genetic variants exist: A1 and A27. Cows like Jerseys, Guernsey, Asian and African cows produce A2 milk while Holstein and Ayrshire cattle breeds predominantly produce A1 milk2. A1 β-casein includes histidine at the 67th position in the peptide chain, whereas A2 β-casein includes proline at this position7.
Digestive enzymes act differently upon A1 and A2 β-casein proteins during digestion process. Beta-casomorphin-7 (BCM-7) peptide is released by digestive enzymes from the A1 β-casein protein but these enzymes cannot split the A2 protein due to presence of proline at that location. So BCM-7 is not released from A2 proteins digestion9.
Digestive Discomfort
It has been reported that BCM-7 is associated with increased gastrointestinal inflammation and worsening of post-dairy digestive discomfort (PD3) symptoms2,5,6. Intolerance to dairy products is a commonly reported gastrointestinal disorder, and is usually attributed to lactose intolerance4. However, based on the gastrointestinal effects of BCM-7, it is possible that intolerance to dairy products in some cases is related to the consumption of A1 β-casein rather than lactose per se6. Based on various studies, the populations consuming milk having more β-casein A2 exhibit a lower occurrence of cardiovascular disease and type 1 diabetes8. People consuming A2 milk had better stool consistency, less incidence of bloating and less abdominal pain5.
Opportunity for Commercialization of A2 Milk
The consumption of milk containing A2 β-casein at the exclusion of A1 β-casein may alleviate or prevent the gastrointestinal disturbances associated with BCM-7. Bovine milk that is free of A1 is now available commercially in a range of countries, and is widely promoted as beneficial for people who suffer from milk intolerances. Infant formula containing casein but free of A1 is now marketed widely in China and Australia and is promoted commercially as being more gentle on the infant digestive system3. Since milk produced commercially in many countries contains a mixture of A1 and A2, there is vast scope for commercialization of A2 milk worldwide since demand for safe A2 milk is ever-increasing.
References
1American Chemical Society. (2019). A comprehensive look at cow’s milk.
2Behera, R., Sahu, A., Mandal, A., Rai, S., Karunakaran, M., & Dutta, T. (2018). A1 versus A2 Milk- Impact on Human Health. International Journal Of Livestock Research, 1. https://doi.org/10.5455/ijlr.20170810113426
3Brooke-Taylor, S., Dwyer, K., Woodford, K., & Kost, N. (2017). Systematic Review of the Gastrointestinal Effects of A1 Compared with A2 β-Casein. Advances In Nutrition: An International Review Journal, 8(5), 739-748. https://doi.org/10.3945/an.116.013953
4Brüssow, H. (2013). Nutrition, population growth and disease: a short history of lactose. Environmental Microbiology, 15(8), 2154-2161. https://doi.org/10.1111/1462-2920.12117
5Ho, S., Woodford, K., Kukuljan, S., & Pal, S. (2014). Comparative effects of A1 versus A2 beta-casein on gastrointestinal measures: a blinded randomised cross-over pilot study. European Journal Of Clinical Nutrition, 68(9), 994-1000. https://doi.org/10.1038/ejcn.2014.127
6Jianqin, S., Leiming, X., Lu, X., Yelland, G., Ni, J., & Clarke, A. (2015). Effects of milk containing only A2 beta casein versus milk containing both A1 and A2 beta casein proteins on gastrointestinal physiology, symptoms of discomfort, and cognitive behavior of people with self-reported intolerance to traditional cows’ milk. Nutrition Journal, 15(1). https://doi.org/10.1186/s12937-016-0147-z
7Ramakrishnan, M., Eaton, T., Sermet, O., & Savaiano, D. (2020). Milk Containing A2 β-Casein ONLY, as a Single Meal, Causes Fewer Symptoms of Lactose Intolerance than Milk Containing A1 and A2 β-Caseins in Subjects with Lactose Maldigestion and Intolerance: A Randomized, Double-Blind, Crossover Trial. Nutrients, 12(12), 3855. https://doi.org/10.3390/nu12123855
8Sodhi, M., Mukesh, M., Kataria, R., Mishra, B., & Joshii, B. (2012). Milk proteins and human health: A1/A2 milk hypothesis. Indian Journal Of Endocrinology And Metabolism, 16(5), 856. https://doi.org/10.4103/2230-8210.100685
9ul Haq, M., Kapila, R., Shandilya, U., & Kapila, S. (2014). Impact of Milk Derived β-Casomorphins on Physiological Functions and Trends in Research: A Review. International Journal Of Food Properties, 17(8), 1726-1741. https://doi.org/10.1080/10942912.2012.712077
