Impact of Diets on Cognitive and Clinical Outcomes in Alzheimer's Disease: A Scoping Review.

Alzheimer's disease (AD) is characterized by beta-amyloid plaques and neurofibrillary tangles, leading to damage of neuronal synapses, negatively impacting memory and cognition. Research efforts have shown the benefit of proper nutrition in reducing the progression of AD and slowing the condition's progression. Specifically, nutritional intake has been demonstrated to influence neuro-inflammatory pathways. Various diets, including ketogenic, Mediterranean, Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, and Dietary Approaches to Stop Hypertension (DASH), have been shown to prevent the onset of AD to different degrees. The primary objective of this scoping review was to assess the impacts of various diets on AD onset and progression to identify unmet needs and gaps in understanding. Following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, peer-reviewed literature was searched using Boolean operators: "Alzheimer's" AND "ketogenic" OR "DASH diet" OR "MIND diet" OR "Mediterranean diet" on EMBASE, MEDLINE, and Web of Science databases. The search was restricted to articles written in English and published in the United States between January 1, 2013, and September 30, 2023. The initial search yielded 121 articles after removing duplicates. After filtering based on inclusion and exclusion criteria, 24 articles were selected for further critical appraisal screening. The critical appraisal yielded 12 articles for the analysis included in this scoping review. This review supported the Mediterranean diet as the most effective in improving outcomes among patients with AD. The Mediterranean diet consists of a high intake of vegetables, fruits, legumes, nuts, olive oil, and unrefined cereals, a moderate intake of fish and wine, and a low intake of dairy products, meat, poultry, and saturated fat. Other diets reviewed, including the DASH and MIND diets, also have promising effects on AD, with less conclusive evidence when compared to the Mediterranean diet. Limitations, including small sample sizes, short durations, and socioeconomic constraints impacting compliance, were noted. This scoping review supports the need for dietary recommendation guidelines for patients with AD.