Observational and ecological studies of dietary advanced glycation end products in national diets and Alzheimer's disease incidence and prevalence

Background: Considerable evidence indicates that diet is an important risk-modifying factor for Alzheimer's disease (AD). Evidence is also mounting that dietary advanced glycation end products (AGEs) are important risk factors for AD. Objective: This study strives to determine whether estimated dietary AGEs estimated from national diets and epidemiological studies are associated with increased AD incidence.Methods: We estimated values of dietary AGEs using values in a published paper. We estimated intake of dietary AGEs from the Washington Heights-Inwood Community Aging Project (WHICAP) 1992 and 1999 cohort studies, which investigated how the Mediterranean diet (MeDi) affected AD incidence. Further, AD prevalence data came from three ecological studies and included data from 11 countries for 1977-1993, seven developing countries for 1995-2005, and Japan for 1985-2008. The analysis used dietary AGE values from 20 years before the AD prevalence data.Results: Meat was always the food with the largest amount of AGEs. Other foods with significant AGEs included fish, cheese, vegetables, and vegetable oil. High MeDi adherence results in lower meat and dairy intake, which possess high AGE content. By using two different models to extrapolate dietary AGE intake in the WHICAP 1992 and 1999 cohort studies, we showed that reduced dietary AGE significantly correlates with reduced AD incidence. For the ecological studies, estimates of dietary AGEs in the national diets corresponded well with AD prevalence data even though the cooking methods were not well known.Conclusion: Dietary AGEs appear to be important risk factors for AD.