OMIA 002033-9913 : A2 milk in Bos taurus

In other species: water buffalo

Possibly relevant human trait(s) and/or gene(s) (MIM number): 115460 (gene)

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal Co-Dominant

Considered a defect: no

Key variant known: yes

Molecular basis: Gallinet et al. (2013): c.245A>C; p.H82P (with respect to accession no. M55158; was previously p.H67P)

Associated gene:

Symbol Description Species Chr Location OMIA gene details page Other Links
CSN2 casein beta Bos taurus 6 NC_037333.1 (85457867..85449173) CSN2 Homologene, Ensembl, NCBI gene


By default, variants are sorted chronologically by year of publication, to provide a historical perspective. Readers can re-sort on any column by clicking on the column header. Click it again to sort in a descending order. To create a multiple-field sort, hold down Shift while clicking on the second, third etc relevant column headers.

WARNING! Inclusion of a variant in this table does not automatically mean that it should be used for DNA testing. Anyone contemplating the use of any of these variants for DNA testing should examine critically the relevant evidence (especially in breeds other than the breed in which the variant was first described). If it is decided to proceed, the location and orientation of the variant sequence should be checked very carefully.

Since October 2021, OMIA includes a semiautomated lift-over pipeline to facilitate updates of genomic positions to a recent reference genome position. These changes to genomic positions are not always reflected in the ‘acknowledgements’ or ‘verbal description’ fields in this table.

OMIA Variant ID Breed(s) Variant Phenotype Gene Allele Type of Variant Source of Genetic Variant Reference Sequence Chr. g. or m. c. or n. p. Verbal Description EVA ID Inferred EVA rsID Year Published PubMed ID(s) Acknowledgements
220 A2 milk CSN2 A2 missense Naturally occurring variant ARS-UCD1.2 6 g.85451298T>G c.245A>C p.(H82P) Note that cattle cannot be genotyped for the A2 allele solely on the basis of the c.245A>C variant because this variant is common to 4 other alleles; see Table 2 of Caroli et al. (2009) J. Dairy Sci. 92, 5335-5352 (Matt McClure, pers. comm.) rs43703011 rs43703011 2013 23102962 Variant coordinates obtained from or confirmed by EBI's Some Effect Predictor (VEP) tool


Note: the references are listed in reverse chronological order (from the most recent year to the earliest year), and alphabetically by first author within a year.
2022 [No authors listed] :
Detection of A2A2 genotype of beta casein protein (<i>CSN2</i>) gene in local, exotic and cross bred cattle in Pakistan. Anim Biotechnol :1-12, 2022. Pubmed reference: 35235484. DOI: 10.1080/10495398.2022.2031204.
Giribaldi, M., Lamberti, C., Cirrincione, S., Giuffrida, M.G., Cavallarin, L. :
A2 Milk and BCM-7 Peptide as Emerging Parameters of Milk Quality. Front Nutr 9:842375, 2022. Pubmed reference: 35571904. DOI: 10.3389/fnut.2022.842375.
2021 de Oliveira, L.S.M., Alves, J.S., Bastos, M.S., da Cruz, V.A.R., Pinto, L.F.B., Tonhati, H., Costa, R.B., de Camargo, G.M.F. :
Water buffaloes (Bubalus bubalis) only have A2A2 genotype for beta-casein. Trop Anim Health Prod 53:145, 2021. Pubmed reference: 33511501. DOI: 10.1007/s11250-021-02591-9.
Gai, N., Uniacke-Lowe, T., O'Regan, J., Faulkner, H., Kelly, A.L. :
Effect of protein genotypes on physicochemical properties and protein gunctionality of bovine milk: A review. Foods 10:, 2021. Pubmed reference: 34681458. DOI: 10.3390/foods10102409.
Hockey, M., Aslam, H., Berk, M., Pasco, J.A., Ruusunen, A., Mohebbi, M., Macpherson, H., Chatterton, M.L., Marx, W., O'Neil, A., Rocks, T., McGuinness, A.J., Young, L.M., Jacka, F.N. :
The Moo'D Study: protocol for a randomised controlled trial of A2 beta-casein only versus conventional dairy products in women with low mood. Trials 22:899, 2021. Pubmed reference: 34895297. DOI: 10.1186/s13063-021-05812-6.
Kay, S.S., Delgado, S., Mittal, J., Eshraghi, R.S., Mittal, R., Eshraghi, A.A. :
Beneficial effects of milk having A2 β-casein protein: Myth or reality? J Nutr :, 2021. Pubmed reference: 33693747. DOI: 10.1093/jn/nxaa454.
Mayer, H.K., Lenz, K., Halbauer, E.M. :
"A2 milk" authentication using isoelectric focusing and different PCR techniques. Food Res Int 147:110523, 2021. Pubmed reference: 34399501. DOI: 10.1016/j.foodres.2021.110523.
2020 Yadav, S., Yadav, N.D.S., Gheware, A., Kulshreshtha, A., Sharma, P., Singh, V.P. :
Oral feeding of cow milk containing A1 variant of β casein induces pulmonary inflammation in male Balb/c Mice. Sci Rep 10:8053, 2020. Pubmed reference: 32415285. DOI: 10.1038/s41598-020-64997-z.
2019 Cieślińska, A., Fiedorowicz, E., Zwierzchowski, G., Kordulewska, N., Jarmołowska, B., Kostyra, E. :
Genetic Polymorphism of β-Casein Gene in Polish Red Cattle-Preliminary Study of A1 and A2 Frequency in Genetic Conservation Herd. Animals (Basel) 9:, 2019. Pubmed reference: 31226807. DOI: 10.3390/ani9060377.
2017 Chia, J.S.J., McRae, J.L., Kukuljan, S., Woodford, K., Elliott, R.B., Swinburn, B., Dwyer, K.M. :
A1 beta-casein milk protein and other environmental pre-disposing factors for type 1 diabetes. Nutr Diabetes 7:e274, 2017. Pubmed reference: 28504710. DOI: 10.1038/nutd.2017.16.
Duarte-Vázquez, M.Á., García-Ugalde, C., Villegas-Gutiérrez, L.M., García-Almendárez, B.E., Rosado, J.L. :
Production of Cow's Milk Free from Beta-Casein A1 and Its Application in the Manufacturing of Specialized Foods for Early Infant Nutrition. Foods 6:, 2017. Pubmed reference: 28704923. DOI: 10.3390/foods6070050.
He, M., Sun, J., Jiang, Z.Q., Yang, Y.X. :
Effects of cow's milk beta-casein variants on symptoms of milk intolerance in Chinese adults: a multicentre, randomised controlled study. Nutr J 16:72, 2017. Pubmed reference: 29070042. DOI: 10.1186/s12937-017-0275-0.
Kirk, B., Mitchell, J., Jackson, M., Amirabdollahian, F., Alizadehkhaiyat, O., Clifford, T. :
A2 Milk Enhances Dynamic Muscle Function Following Repeated Sprint Exercise, a Possible Ergogenic Aid for A1-Protein Intolerant Athletes? Nutrients 9:, 2017. Pubmed reference: 28134840. DOI: 10.3390/nu9020094.
Massella, E., Piva, S., Giacometti, F., Liuzzo, G., Zambrini, A.V., Serraino, A. :
Evaluation of bovine beta casein polymorphism in two dairy farms located in northern Italy. Ital J Food Saf 6:6904, 2017. Pubmed reference: 29071248. DOI: 10.4081/ijfs.2017.6904.
Rangel, A.H.N., Zaros, L.G., Lima, T.C., Borba, L.H.F., Novaes, L.P., Mota, L.F.M., Silva, M.S. :
Polymorphism in the Beta Casein Gene and analysis of milk characteristicsin Gir and Guzerá dairy cattle. Genet Mol Res 16:, 2017. Pubmed reference: 28549202. DOI: 10.4238/gmr16029592.
2016 Caroli, A.M., Savino, S., Bulgari, O., Monti, E. :
Detecting β-Casein Variation in Bovine Milk. Molecules 21:141, 2016. Pubmed reference: 26821001. DOI: 10.3390/molecules21020141.
Dai, R., Fang, Y., Zhao, W., Liu, S., Ding, J., Xu, K., Yang, L., He, C., Ding, F., Meng, H. :
Identification of alleles and genotypes of beta-casein with DNA sequencing analysis in Chinese Holstein cow. J Dairy Res 83:312-6, 2016. Pubmed reference: 27600965. DOI: 10.1017/S0022029916000303.
Gholami, M., Hafezian, S.H., Rahimi, G., Farhadi, A., Rahimi, Z., Kahrizi, D., Kiani, S., Karim, H., Vaziri, S., Muhammadi, S., Veisi, F., Ghadiri, K., Shetabi, H., Zargooshi, J. :
Allele specific-PCR and melting curve analysis showed relatively high frequency of β-casein gene A1 allele in Iranian Holstein, Simmental and native cows. Cell Mol Biol (Noisy-le-grand) 62:138-143, 2016. Pubmed reference: 27894411.
Jianqin, S., Leiming, X., Lu, X., Yelland, G.W., Ni, J., Clarke, A.J. :
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. Nutr J 15:35, 2016. Pubmed reference: 27039383. DOI: 10.1186/s12937-016-0147-z.
Jianqin, S., Leiming, X., Lu, X., Yelland, G.W., Ni, J., Clarke, A. :
Erratum to: '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'. Nutr J 15:45, 2016. Pubmed reference: 27130280. DOI: 10.1186/s12937-016-0164-y.
2014 Ho, S., Woodford, K., Kukuljan, S., Pal, S. :
Comparative effects of A1 versus A2 beta-casein on gastrointestinal measures: a blinded randomised cross-over pilot study. Eur J Clin Nutr 68:994-1000, 2014. Pubmed reference: 24986816. DOI: 10.1038/ejcn.2014.127.
2013 Gallinat, J.L., Qanbari, S., Drögemüller, C., Pimentel, E.C., Thaller, G., Tetens, J. :
DNA-based identification of novel bovine casein gene variants. J Dairy Sci 96:699-709, 2013. Pubmed reference: 23102962. DOI: 10.3168/jds.2012-5908.
Givens, I., Aikman, P., Gibson, T., Brown, R. :
Proportions of A1, A2, B and C β-casein protein variants in retail milk in the UK. Food Chem 139:549-52, 2013. Pubmed reference: 23561144. DOI: 10.1016/j.foodchem.2013.01.115.
2012 Sodhi, M., Mukesh, M., Kataria, R.S., Mishra, B.P., Joshii, B.K. :
Milk proteins and human health: A1/A2 milk hypothesis. Indian J Endocrinol Metab 16:856, 2012. Pubmed reference: 23087884. DOI: 10.4103/2230-8210.100685.
2011 Clemens, R.A. :
Milk A1 and A2 peptides and diabetes. Nestle Nutr Workshop Ser Pediatr Program 67:187-95, 2011. Pubmed reference: 21335999. DOI: 10.1159/000325584.
2007 Kamiński, S., Cieslińska, A., Kostyra, E. :
Polymorphism of bovine beta-casein and its potential effect on human health. J Appl Genet 48:189-98, 2007. Pubmed reference: 17666771. DOI: 10.1007/BF03195213.
2006 Allison, A.J., Clarke, A.J. :
Further research for consideration in 'the A2 milk case'. Eur J Clin Nutr 60:921-4; reply 924-5, 2006. Pubmed reference: 16189549. DOI: 10.1038/sj.ejcn.1602276.
Bell, S.J., Grochoski, G.T., Clarke, A.J. :
Health implications of milk containing beta-casein with the A2 genetic variant. Crit Rev Food Sci Nutr 46:93-100, 2006. Pubmed reference: 16403684. DOI: 10.1080/10408390591001144.
Woodford, K.B. :
A critique of Truswell's A2 milk review. Eur J Clin Nutr 60:437-9, 2006. Pubmed reference: 16278689. DOI: 10.1038/sj.ejcn.1602322.
2005 Truswell, A.S. :
The A2 milk case: a critical review. Eur J Clin Nutr 59:623-31, 2005. Pubmed reference: 15867940. DOI: 10.1038/sj.ejcn.1602104.
2004 Smith, W.B., Thompson, D., Kummerow, M., Quinn, P., Gold, M.S. :
A2 milk is allergenic. Med J Aust 181:574, 2004. Pubmed reference: 15540973.
1995 Lindersson, M., Lundén, A., Andersson, L. :
Genotyping bovine milk proteins using allele discrimination by primer length and automated DNA sizing technology. Anim Genet 26:67-72, 1995. Pubmed reference: 7733509.
1988 Bonsing, J., Ring, J.M., Stewart, A.F., Mackinlay, A.G. :
Complete nucleotide sequence of the bovine beta-casein gene. Aust J Biol Sci 41:527-37, 1988. Pubmed reference: 3271384.
1984 Ng-Kwai-Hang, K.F., Hayes, J.F., Moxley, J.E., Monardes, H.G. :
Association of genetic variants of casein and milk serum proteins with milk, fat, and protein production by dairy cattle. J Dairy Sci 67:835-40, 1984. Pubmed reference: 6725728. DOI: 10.3168/jds.S0022-0302(84)81374-0.

Edit History

  • Created by Frank Nicholas on 25 Aug 2016
  • Changed by Frank Nicholas on 25 Aug 2016
  • Changed by Frank Nicholas on 27 Aug 2016
  • Changed by Imke Tammen2 on 22 Aug 2021