Health Implications of Milk Containing β-Casein with the A² Genetic Variant

Milk from dairy cows has long provided a high quality source of protein and selected micronutrients such as calcium to most populations. Recently, a relationship between disease risk and consumption of a specific bovine β-casein fraction either A ¹ or A ² genetic variants has been identified. Populations, which consume milk containing high levels of β-casein A ² variant, have a lower incidence of cardiovascular disease and type 1 diabetes. Furthermore, consumption of milk with the A ² variant may be associated with less severe symptoms of autism and schizophrenia. The mechanism of action focuses on β-casein A ¹ and related forms preferentially that are able to produce a bioactive opioid peptide, β-casomorphin-7 (β-CM-7) during digestion. Infants may absorb β-CM-7 due to an immature gastrointestinal tract. Adults, on the other hand, appear to reap the biological activity locally on the intestinal brush boarder. β-CM-7 can potentially affect numerous opioid receptors in the nervous, endocrine, and immune systems. Whether there is a definite health benefit to milk containing the A ² genetic variant is unknown and requires further investigation.

Keywords:

• bovine milk
• β-casein
• β
• -casomorphin

Notes

*Adapted from Laugesen and Elliott, 2003. Data were grouped in 5-years segments over a 20-year period.

*Adapted from Elliott et al., 1999. r = +0.982; P = 0.01.