Growing evidence suggests that diet quality plays an important role in determining future disease risk. Lifestyle diseases associated with poor quality diet include cardiovascular disease, cancer, diabetes, metabolic syndrome and obesity. However, much of the research to date has focussed on the role of isolated nutrients in disease protection, a methodology borrowed from the pharmaceutical industry. The problem with this approach is that the effects of individual food components are very small and hard to detect amongst the many confounding variables. Increasingly, nutritional scientists are realising that assessing groups of foods or whole diets is a better determinant of disease risk than considering isolated food units. The synergistic effects of beneficial foods, when incorporated into a healthy diet is typified by the research performed on the Mediterranean diet. Studies investigating this diet have consistently shown beneficial effects above and beyond those expected from any individual food component contained within.
This synergistic approach to dietary analysis was illustrated by research published in the Journal of Nutrition in 20121. Here researchers used a nested case control study involving 1224 participants to investigate the effects of dietary patterns on cardiovascular disease risk. The diets of subjects who had confirmed cases of coronary heart disease, or had suffered a fatal or non-fatal myocardial infarction were compared with the diets of age, race and enrolment date matched healthy subjects. Diets high in carbohydrate, vegetable protein, fibre, dietary vitamin K, folate, carotenoids, α-linolenic acid (ALA, C18:3 (n-3)), linoleic acid (LA, C18:2 (n-6)) and supplemental calcium and vitamin D were associated with a lower risk of cardiovascular disease than diets rich in animal protein, arachidonic acid (AA, C20:4 (n-6)) vitamin D and calcium. Diets high in energy, total fat and trans fatty acids were associated with an increased risk of cardiovascular disease.
These results suggest that a dietary pattern similar to that seen in the Mediterranean diet is protective of cardiovascular disease and that one similar to a traditional Western diet increases cardiovascular disease risk. Adjusting the results for body mass index and systolic blood pressure attenuated the benefits associated with the high quality diet, and adjusting the results for smoking, education and physical activity attenuated the risk associated with the lower quality diet. Therefore those subjects consuming a higher quality diet had lower body mass indexes, whereas those consuming lower quality diets performed less physical activity, had lower educational status and were more likely to smoke. Interestingly, the amount of carbohydrate consumed by the three groups was 61, 52 and 44 % for the high to low quality diet. However, the authors suggested that type, rather than amount of carbohydrate, was a likely confounding variable.