Nutrition and neurodegeneration: epidemiological evidence and challenges for future research

Abstract

The prevention of dementias, such as Alzheimer's disease (AD), is a growing public health concern, due to a lack of effective curative treatment options and a rising global prevalence. Various potential risk or preventive factors have been suggested by epidemiological research, including modifiable lifestyle factors such as diet. Current epidemiological data are in favour of a protective role of certain micronutrients (B vitamins related to homocysteine metabolism, the anti‐oxidant vitamins C and E, flavonoids, polyunsatured omega‐3 fatty acids, vitamin D) and macronutrients (fish) in the prevention of cognitive decline and dementia/AD. Some factors have been targeted by interventions tested in randomized controlled trials (RCTs), but many of the results are conflicting with observational evidence. Epidemiological analysis of the relations between nutrient consumption and cognitive decline is complex and it is highly unlikely that a single component plays a major role. In addition, since multiple factors across the life course influence brain function in late life, multidomain interventions might be more promising in the prevention of cognitive decline and dementia/AD. Designing such trials remains very challenging for researchers. The main objective of this paper is to review the epidemiologic data linking potential protective factors to cognitive decline or dementia/AD, focusing particularly on the roles of adiposity, caloric restriction, micro (group B vitamins related to homocysteine metabolism, the anti‐oxidant vitamins C and E, flavonoids, polyunsatured omega‐3 fatty acids, vitamin D) and macronutrients (fish). Limitations of the current data, divergence with results of interventional prevention studies and challenges for future research are discussed.

Prevention of Alzheimer's disease: The role of the Mediterranean diet

“…Since then, it has been increasing exponentially, and it is now considered a 21 st century epidemic, affecting approximately 26 million people worldwide and one quarter of the people aged above 85 years [8][9][10][11] .…”

“…Thus, in the absence of curative strategies, prevention of Alzheimer's disease through risk factor management is essential 11,18 . In fact, it is estimated that delaying the onset of the clinical stage of Alzheimer's disease by 1 and 5 years would decrease its prevalence by 25 and 50%, respectively, after 5 years of implementation of the preventive measures 11 .…”

“…In fact, it is estimated that delaying the onset of the clinical stage of Alzheimer's disease by 1 and 5 years would decrease its prevalence by 25 and 50%, respectively, after 5 years of implementation of the preventive measures 11 . In addition, while improving clinical outcomes, an efficient preventive strategy would also reduce financial costs and, consequently, lighten the burden of Alzheimer's disease on health care systems 13 .…”

“…In recent years several studies have shown the benefits of healthy nutrition on several chronic diseases, such as cardiovascular disease, cancer, Parkinson's disease, and diabetes 11,28 . Hence, since diet constitutes one of the most important modifiable environmental factors, there has been increasing interest on the potential beneficial role of diet also on Alzheimer's disease 19,29 .…”

“…The beneficial role of the MeDi on agerelated changes in cognitive function, predementia syndromes, and dementia probably occurs through multiple pathways, namely vascular and nonvascular ones 11 . Accordingly, the MeDi is known to reduce the risk of cardiovascular diseases and mortality; therefore, vascular mechanisms could actually be responsible for the protective role of the MeDi on Alzheimer's disease 5 .…”