Abstract
Purpose: To review published evidence that the lactose in a high intake of milk is a possible risk factor for ischaemic heart disease (IHD). Design: Literature review of studies published since 1959. Materials and Methods: The evidence is reviewed under the headings Pathological Studies, Clinical Studies, Prospective Epidemiological Studies, Population (Ecological) Studies and Epidemiological Paradoxes, reflecting its multidisciplinary sources. Within each section and subsection the reports are considered chronologically as far as the subject matter allows. The focus of the necessarily brief summaries of the reports is on the findings. Any individual methodological weakness is held to be counterbalanced by the number and variety of studies with consistent findings. The review includes associations of persistent high lactase activity in adulthood with intake of milk and lactose, and with IHD. A considerable number of the sources are not directly cited but are to be found in various referenced reviews. Conclusions: The evidence and biological plausibility are considered to be sufficiently convincing to warrant epidemiological and scientific investigations aimed at proving or refuting a lactose hypothesis of a causal association with IHD. Appropriate agencies should ensure that the hypothesis is tested. Some possible investigations are proposed.