Abstract:
Aim To test the correlation of per capita A1 ß-casein (A1/capita) and milk protein
with: 1) ischaemic heart disease (IHD) mortality; 2) Type 1 (insulin-dependent)
diabetes mellitus (DM-1) incidence.
Methods A1/capita was estimated as the product of per capita cow milk and cream
supply and its A1 ß-casein content (A1/ ß) (calculated from herd tests and breed
distribution, or from tests of commercial milk), then tested for correlation with: 1)
IHD five years later in 1980, 1985, 1990 and 1995, in 20 countries which spent at
least US $1000 (purchasing power parities) per capita in 1995 on healthcare; 2) DM-1
at age 0–14 years in 1990–4 (51 were surveyed by WHO DiaMond Project; 19 had
A1 data). For comparison, we also correlated 77 food, and 110 nutritive supply FAO
(Food and Agriculture Organization)-based measures, against IHD and DM-1.
Results For IHD, cow milk proteins (A1/capita, r = 0.76 , p <0.001; A1/capita
including cheese, r = 0.66; milk protein r = 0.60, p = 0.005) had stronger positive
correlations with IHD five years later, than fat supply variables, such as the
atherogenic index (r = 0.50), and myristic, the 14-carbon saturated fat (r = 0.48, p
<0.05). The Hegsted scores for estimating serum cholesterol (r = 0.42); saturated fat (r
= 0.37); and total dairy fat (r = 0.31) were not significant for IHD in 1995. Across the
20 countries, a 1% change in A1/capita in 1990 was associated with a 0.57% change
in IHD in 1995. A1/capita correlations were stronger for male than female mortality.
On multiple regression of A1/capita and other food supply variables in 1990, only
A1/capita was significantly correlated with IHD in 1995.
DM-1 was correlated with supply of: A1/capita in milk and cream (r = 0.92, p
<0.00001); milk and cream protein excluding cheese (r = 0.68, p <0.0001); and with
A1/ß in milk and cream (r = 0.47, p <0.05). Correlations were not significant for A2,
B or C variants of milk b-casein. DM-1 incidence at 0–4, 5–9 and 10–14 years was
equally correlated (r = 0.80, 0.81, 0.81 respectively) with milk protein supply. A 1%
change in A1/capita was associated with a 1.3% change in DM-1 in the same
direction.
Conclusions Cow 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 – providing an alternative hypothesis to explain the high
IHD mortality rates in northern compared to southern Europe.
For DM-1, this study confirms Elliott’s 1999 correlation on 10 countries for
A1/capita,1 but not for B ß-casein/capita. Surveys of A1 b-casein consumption in twoyear-
old Nordic children, and some casein animal feeding experiments, confirm the
A1/capita and milk protein/capita correlations. They raise the possibility that intensive dairy cattle breeding may have emphasised a genetic variant in milk with adverse
effects in humans. Further animal research and clinical trials would be needed to
compare disease risks of A1-free versus ‘ordinary’ milk.