ecently a partial shift has occurred in the way the nutritional sciences approach research. Traditionally, single isolated foods were assessed for their health effects, a model based largely on the one used prominently in medicine since its inception. However, a broader, less focused approach to consider diet as a whole has proved successful in advancing the literature with regard future health risk. In fact, this approach is more suited to nutrition where each component is interrelated, and from this methodology the concept of overall diet quality has become prominent. A holistic approach acknowledges the synergist effects of nutrients, whereby traditional eating plans such as the Mediterranean diet can improve overall health and decrease the risk of certain diseases. Low quality diets such as the traditional Western diet are now broadly associated with a number of diseases including cardiovascular disease and cancer.
A number of studies have linked poor quality diet with cognitive decline. Recently researchers1 investigated the effects of overall diet quality on the cognitive ability of middle aged persons. Dietary habits of 3054 subjects men and women with a mean age of 45 years were assessed with 24 hour dietary records, and a traditional Western diet and a healthy eating diet were identified. Cognitive performance was assessed with a number of neuropsychological tests that challenged different mental capacities. The healthy eating plan was associated with better global cognitive function and verbal memory. However, when the authors investigated energy intake, they found that these associations became stronger in individuals consuming below average calories for their gender (<2490 and <1810 kcal for men and women, respectively). Therefore higher quality diets in middle aged individuals appear to benefit cognitive function, particularly if they comprise less energy dense food.
This supports previous data showing that adherence to less energy dense diets such as the traditional Mediterranean diet is associated with improved cognitive function. In this study the healthy dietary pattern was characterised by consumption of fruit, whole grains, fresh dairy products, vegetables, breakfast cereal, tea, vegetable fat, nuts and fish, and low intakes of refined grains, meat, poultry, animal fat and processed meat. This provided higher intakes of fibre, calcium, β-carotene, folic acid, vitamin E, vitamin C, n-3 fatty acids and n-6 fatty acids, and is therefore not dissimilar to the Mediterranean diet. The interesting finding of this study was the stronger association between cognition and healthy diet with lower energy intakes. This may suggest that energy density is an additional factor that needs to be considered when assessing the quality of the diet. The highest quality diets may therefore be those which contain micronutrient rich energy poor foods.
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