Beta Caseins and Heart Disease
The link between beta casein variant consumption & Ischaemic Heart disease
This section summarises and presents references to a number of studies, which report connections between the consumption of milk protein variant beta casein A1 (A1) and ischaemic heart disease (IHD).
The principal publications regarding the connection between A1 and IHD can be divided under the following subheadings:
1) Epidemiology comparing the per capita intake of A1 as compared with the mortality rates for IHD, both within a country and across a number of countries,
2) Animal feeding studies investigating the differential effects of feeding A1 vs. A2 casein diets to NZ white rabbits,
3) Other studies that lend evidence to the link between A1 consumption and the development and/or progression of heart disease.
Epidemiology
The connection between beta-casein A1 consumption and heart disease was first drawn following epidemiological studies [1]. In 1995 Dr McLachlan noted a strong correlation between IHD and A1 consumption (r2 = 0.86), both between countries and within a country (where the mean A1 content of milk & thus the per capita consumption varies between regions).
In January 2003, Laugesen and Elliott published an epidemiological study concluding that A1 ß-casein per capita supply in milk and cream (A1/capita) was significantly and positively correlated with IHD in 20 affluent countries five years later over a 20-year period. [2]
Animal Feeding Trials
Supporting the early epidemiological work, was the observation that the total casein, in comparison to other sources of dietary protein, is a potentiator of heart disease, or related conditions such as hypercholesterolemia, in rabbits [3], [4], [5], [6], [7], pigs [8] and monkeys [9], [10]. However, no work had at this stage been performed to identify what element(s) of casein, which includes alpha, beta and kappa caseins and variants thereof, is atherogenic.
In 2002, a rabbit feeding study was commissioned by a2 Corporation and performed by Prof. Julie Campbell at the Wesley Research Institute (Brisbane). The study indicated a causative link between A1 consumption and the development and progression of arterial lesions in this animal model, and thus provides support for the hypothesis linking A1 to the biological processes leading to arterial damage and heart disease. This work was published by the journal Atherosclerosis [11].
Further Studies
Further to epidemiological studies and animal feeding trials, work on beta casomorphin 7 has been shown to affect processes involved with arterial disease - these are outlined in "Studies on the Differential Digestion Products of beta casein types"
Of particular relevance is the observation that BCM-7 has been shown to catalyse the oxidation of LDL in a non cationic dependent fashion [12].
In support of conclusions drawn by Professor Campbell are published observations that cows milk infant formula fed infants raise antibodies to oxidised LDL at 10 times the rate of those who were breast fed [13], [14], [15]. This also adds further evidence to the belief that consumption of beta casein A1 may lead to the oxidation of LDL and thus contribute to the progression and development of arterial plaques and thus IHD. These observations were further supplemented in a letter to Atherosclerosis (March 2004 Issue) [16] where a distinction was made between male and female baby's responses to infant formula feeding (milk protein); the former group exhibiting a highly significant increase (an order of magnitude) in antibodies to oxLDL in relation to breast fed feeding.
References:
[3] Meeker DR, Kesten HD. Effect of high protein diet on experimental atherosclerosis in rabbits . Arch. Path. 1941 : 31 : 147-62
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