In a recent narrative review article, Italian researchers from the University of Bari Aldo Moro, Bari, suggest that the Mediterranean diet may be the model diet to follow to slow the development of Alzheimer’s disease.
Risk of Alzheimer’s disease increases with age, and clearly there is a need to slow onset of Alzheimer’s disease as life expectancy continues to rise. In 2013, in the United States, 5 million of the total 5.2 million Americans with Alzheimer’s disease were over the age of 65. These numbers are estimated to rise to 13.8 million by 2050, according to the Alzheimer’s Association.
In the absence of treatment for Alzheimer’s disease, making dietary and lifestyle changes may be an effective approach to delay its onset. However, these changes need to be made at an early age given that the asymptomatic phase of Alzheimer’s disease may be present for more than twenty years before symptoms of this debilitating disease appear.
To enable early diagnosis of Alzheimer’s disease, in 2011 the National Institute of Aging and Alzheimer’s Association revised diagnosis criteria used since 1984. Although not standardized for clinical diagnosis, the proposed three stages include: preclinical Alzheimer’s disease; mild cognitive impairment due to Alzheimer’s disease; and dementia due to Alzheimer’s disease.
Although individual nutrients and foods that makeup the Mediterranean diet are known to protect against cognitive decline, higher adherence to the Mediterranean diet as a whole appears to slow cognitive decline that ultimately leads to Alzheimer’s disease. Published in the April 2014 issue of Current Nutrition Reports, the review article reports that higher adherence to the Mediterranean diet may also lower risk of frailty, a physical condition associated with age and increased risk of cognitive decline.
Furthermore, the article found that adherence to the Mediterranean diet may be beneficial at all stages of Alzheimer’s disease because it slows cognitive decline; delays progression from mild cognitive impairment to dementia due to Alzheimer’s disease; and also reduces risk of death from Alzheimer’s disease.
Of the two randomized clinical trials conducted on Mediterranean diet, the 6.5‑year follow-up PREDIMED-NAVARRA study reported that supplementing the Mediterranean diet with extra-virgin olive oil or mixed nuts enhanced cognition, while the shorter, ten-day follow-up study reported inconsistent results. Another benefit of following the Mediterranean diet, according to some studies, is a reduction in frailty and an increase in physical activity in older adults
Among other diets, the Dietary Approaches to Stop Hypertension diet or the DASH diet recommended for Americans who have hypertension, has also been found to be effective in slowing progression of Alzheimer’s disease. Like the Mediterranean diet, the DASH diet recommends higher consumption of vegetables, fruits, whole grains, low-fat dairy, nuts, fish, and poultry while limiting intake of red meat, salt and sweet foods and beverages. A number of population-based studies have also found that consumption of healthy diets based on dietary patterns similar to the Mediterranean and DASH diets, improved cognitive functions and lowered risk of Alzheimer’s disease.
Although more research in the form of randomized clinical trials is needed, most studies reviewed in this article suggest that adoption of the Mediterranean diet as a model diet in early to mid-life may be beneficial for delaying onset of Alzheimer’s disease.