In recent decades there has been a significant increase in life expectancy. However, this has not been accompanied by a commensurate increase in quality of life, with the incidence of dementia rising considerably in latter stages. This increase in the incidence of non-communicable diseases could be explained mainly by changes in lifestyle in today´s society. Living in cities and the drift towards a more sedentary lifestyle, together with the lack of time for cooking and the high availability of ultraprocessed foods on the market have established a much less healthy way of life, contributing to cognitive decline. In the absence of effective treatment for this kind of pathology, prevention through lifestyle is particularly important, with diet being the easiest factor to modify.
Dementias are complex pathologies interrelated with many other non-communicable diseases, such as obesity, diabetes or hypertension. Recently, the influence on cognitive impairment of factors such as the composition of the microbiota and the regulation of epigenetic mechanisms is becoming particularly important. In this work these risk factors are studied, their relationship with the development of dementias and their prevention through diet, with the aim of determining which dietary patterns would also be beneficial in preventing the different types of dementia. Similarly, the influence of the microbiota and the main epigenetic mechanisms on cognitive impairment and its modulation through diet are analysed. Certain dietary guidelines are drawn from this analysis which could reduce the risk of developing dementia.
As a result, the benefits of a good supply of fibre, as well as antioxidant molecules such as polyphenols, certain minerals and vitamins, are highlighted. With regard to macronutrients, it is important to reduce the consumption of simple carbohydrates, prioritising complex ones, and to give preference to monounsaturated and polyunsaturated ω-3 fats over saturated and ω-6 fatty acids. Based on this, priority should be given to foods of vegetable origin, always varied, combining different fruits, vegetables, legumes, nuts and seeds. Likewise, within foods of animal origin, priority should be given to oily fish and chicken, reducing the consumption of red and processed meats as much as possible. Of course, the diet should be based primarily on natural or poorly processed foods, excluding as far as possible ultraprocessed foods, due to their high content of saturated fats and refined sugars.
This composition of the diet is similar to that of diets such as the Mediterranean diet or DASH (Dietary Approaches to Stop Hypertension), which have been n to be effective in preventing dementia in situations of high adherence. In addition, the combination of both diets has given rise to the MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diet, designed specifically for the prevention of this type of pathology, which is effective with lower adherence than previous diets. In this way, the ability of diet and lifestyle to reduce cognitive decline with age is evident, either through the reduction of risk factors or through direct interaction with mechanisms involved in the development of dementias. It is expected that the beneficial effect of high adherence to these diets will be increased if combined with other preventive measures, such as exercise, both physical and mental, avoiding smoking, good sleeping or social activity, which should be analysed in future studies.