Abstract
Purpose: To investigate the evidence linking coronary heart disease (CHD) deaths with milk consumption, and the evidence against such a link. Design: Literature-based review, together with some statistical analysis. Materials and Methods: Analysis of data from a Medline search and standard statistical sources. Results: Several studies have been published showing a high positive correlation between milk consumption in different countries and rates of death a few years later from CHD. One investigation showed that countries which reduced milk consumption later had reduced rates of CHD death, while the only country studied which increased its milk consumption had an increased rate of CHD death. A variety of possible reasons for a link between milk and CHD have been suggested. On the other hand, several studies of smaller groups of people suggest that milk does not correlate with CHD. These studies have serious weaknesses. In no case was there any attempt to find the total exposure to milk, in all foods and drinks. In some studies, age and social class were ignored. One study, widely quoted as showing that CHD is not caused by milk consumption, was actually concerned with strokes. However, CHD deaths are negatively correlated with deaths from strokes. The Masai drink much milk, but it is fermented. They do have atherosclerosis but rarely die of CHD because of the large lumen of their arteries, and probably because few live long enough. A reason why affluent countries tend to have a higher incidence of CHD may be that people susceptible to CHD are the same as those susceptible to infection. In poorer countries, they tend to die of infection before they would have died of heart disease. These susceptible people may be those with clinical or subclinical degrees of hypothyroidism. Conclusions: Milk consumption does appear to be strongly related to CHD death in communities where susceptible people live long enough. Research into the diets of large numbers of people could usefully be preceded by sampling the questions on a subgroup to determine if the data collected will give accurate information on total milk consumption. A randomized controlled study on the effects of a milk-free diet on people with angina would be worthwhile.