Effects of A1 versus A2 milk on cardiometabolic risk in overweight and obese Australians

None listed

Obesity significantly increases the risk of developing metabolic syndrome (MS), which is associated with increased cardiovascular morbidity/mortality. Presently, there is fierce debate surrounding the effects of the A1 beta-casein protein variant (A1) in bovine milk compared to the progenitor A2 variant (A2) with respect to their relative impact on MS risk factors. Most milk and milk products available commercially in Australia contain the A1 protein from dairy cows which carry the A1 gene. The A1 variant in Australian dairy cattle is the result of a mutation from the A2 gene in European herds ~5,000 years ago. Alternatively, milk produced by cows specially selected and then bred to produce only the original A2 beta-casein type is also available in Australia, but it is a specialty milk brand. Ample evidence now suggests that A1 milk beta-casein can affect features of MS and so has important public health implications. Given the Australian Dietary Guidelines recommend 2.5-4 dairy serves/day, the effect of milk variety on MS warrants investigation. A1 and A2 protein have differences in bioactivity on digestion, due to the release of the 7-amino acid opioid peptide beta-casomorphin-7 (BCM-7), from the digestion of A1 but not A2. In vitro and animal studies have demonstrated that BCM-7 oxidises low density lipoprotein (LDL)-cholesterol and increases levels of the inflammatory marker myeloperoxidase, both of which are implicated in the development of heart disease. A1 beta-casein and BCM-7 also stimulate inflammatory markers and so may contribute to the overall inflammatory milieu in MS. We have also shown in our recent randomised cross-over study that A1 milk stimulates differences in gastrointestinal inflammatory responses compared to A2 milk. The aim of the current proposed project is to investigate the difference between A1 and A2 beta-casein protein containing milk on cardiovascular and metabolic risk factors in overweight/obese individuals. Simple and affordable nutrition interventions that can positively affect modifiable risk factors for heart disease and T2D in Australian adults are needed. If the predicted differences between A1 and A2 beta-casein containing milk on cardiometabolic risk outcomes are found, it will have important ramification for public health and the prevention of chronic illness like cardiovascular disease. Dairy farmers would be advised to choose A2 semen for their dairy breeding programs to change to the A2 milk type for Australian consumers. We hypothesise that A1, but not A2 beta-casein containing milk, will correspond to shifts in cardiometabolic risk factors mediated via BCM-7 in blood. In contrast, we propose that A2 beta-casein containing milk will have a neutral, rather than beneficial, effect on metabolic syndrome factors. Thus, the hypothesis implies that A2 will do no harm, while the mutated A1 variant may increase the risk of chronic disease at a population health level.

No related papers found yet.