Nutritional research has undergone a paradigm shift in recent years. In this regard, diet quality as a whole, rather than any individual component of that diet, is starting to be understood as the defining factor in health. That is not to say that investigations into the physiological effects of isolated dietary components are not useful or justified. But more to say that it is the interaction of all foods in a diet that determine if the pathway taken is that of health or disease. Fixation on individual dietary components, or individual chemicals within those components, is a reductionist ideology that pervades science and in this regard nutrition was influenced by other branches of science, most notably pharmacology. But foods are not drugs, and the way that nutrients are absorbed, metabolised, interact and are excreted is not the same as for xenobiotic pharmaceuticals. Within the last decade therefore a slow transition to the study of diet quality has occurred, and this holistic view is beginning to supercede the reductionist view that went before.
Traditionally lipids such as cholesterol and saturated fat were theorised to be the main causative dietary components that contributed to cardiovascular disease. This viewpoint has always been controversial however, because the scientific evidence for such an association was weak at best. However, following early work by Ancel Keys, this theory has dogmatically been defended by ‘scientists’. The fact that many factors could increase the risk of cardiovascular disease including high plasma homocysteine concentrations, low vitamin C plasma concentrations and low vitamin D plasma concentrations suggested that it was not a single factor that lead to cardiovascular disease, but a number of factors that resulted from a low quality diet. Further, that high quality diets are in fact protective of cardiovascular disease is evidenced in the nutritional literature. For example, the associations between prospective dietary food scores and cardiovascular disease risk have been measured in British men between 60 and 79 years of age1.
The researchers analysed the diets of the men and assigned them a score based on the closeness of the diet to that of a Healthy Diet Indicator (based on World Health Organisation guidelines) or that of an Elderly Dietary Index (based on the Mediterranean diet). The results showed that men with diets most closely matching the Elderly Dietary Index had a 25 % lower risk of all cause mortality, a 21 % lower risk of cardiovascular mortality, and a 44 % reduction in coronary heart disease events, compared to those men whose diets least closely matched the Elderly Dietary Index. However, adherence to diets that matched the Healthy Diet Indicator were not significantly associated with beneficial outcomes. Therefore the Elderly Dietary Index, which is in turn based on the Mediterranean diet, appears to be more useful at assessing diet quality than the Healthy Diet Indicator. These results therefore support other studies that show beneficial effects to consumption of a Mediterranean style diet.
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