Effects of Nutrition on Cognitive Function in Adults with or without Cognitive Impairment: A Systematic Review of Randomized Controlled Clinical Trials.

Laia Gutierrez,Mercedes Atienza,Mònica Bulló,Antoni Camins,Agustín Ruiz,Alexandre Folch,Christopher Papandreou,Jaume Folch,Melina Rojas,José Luis Cantero

doi:10.3390/nu13113728

Abstract

New dietary approaches for the prevention of cognitive impairment are being investigated. However, evidence from dietary interventions is mainly from food and nutrient supplement interventions, with inconsistent results and high heterogeneity between trials. We conducted a comprehensive systematic search of randomized controlled trials (RCTs) published in MEDLINE-PubMed, from January 2018 to July 2021, investigating the impact of dietary counseling, as well as food-based and dietary supplement interventions on cognitive function in adults with or without cognitive impairment. Based on the search strategy, 197 eligible publications were used for data abstraction. Finally, 61 articles were included in the analysis. There was reasonable evidence that dietary patterns, as well as food and dietary supplements improved cognitive domains or measures of brain integrity. The Mediterranean diet showed promising results, whereas the role of the DASH diet was not clear. Healthy food consumption improved cognitive function, although the quality of these studies was relatively low. The role of dietary supplements was mixed, with strong evidence of the benefits of polyphenols and combinations of nutrients, but with low evidence for PUFAs, vitamin D, specific protein, amino acids, and other types of supplements. Further well-designed RCTs are needed to guide the development of dietary approaches for the prevention of cognitive impairment.

Highlights

Since 2018, 3 randomized controlled trials (RCTs) evaluating the effect of following a Mediterranean diet enriched with either fresh lean pork (MedPork study) or dairy products (MedDairy study) or high phenolic early harvest extra virgin olive oil (HP-EH-EVOO) in cognitively healthy subjects have been conducted, showing increased processing speed as compared to a low-fat diet [27,28] and better scores on global cognition, attention and fluency tasks compared to a Mediterranean diet not supplemented with high-phenolic EVOO [29]
The studies included in this review support that healthy dietary patterns, specific foods and dietary supplements can (a) improve memory, language, attention and concentration, executive functions, psychomotor speed and further cognitive domains, and (b) increase blood perfusion in areas typically related to AD
The existing evidence from RCTs over the last four years is in line with most of the previous findings already reported in the preceding systematic reviews

Summary

Introduction

Dementia represents a serious public health challenge for elderly people [1], while. Alzheimer’s disease (AD), the most common type of dementia, has become one of the biggest mental burdens [2]. Except for the recent and controversial approval of Aduhelm to treat patients with Alzheimer’s disease, there are no effective treatments to prevent or delay its progression, only for treating the symptoms of mild to moderate dementia [3]. There is an urgent need to identify effective strategies to prevent dementia. It is well recognized that mild cognitive impairment (MCI) precedes AD [4,5]; new evidence suggests that subtle and silent pathological brain changes associated with subjective decline are present in subjects with subjective cognitive decline (SCD), defined as a self-reported decline in cognitive performance compared to an individual’s previous level of functioning, which cannot be determined by neuropsychological tests [6]

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Discussion

Conclusion