A scoping review of immunonutrients with antioxidant properties and their effect on mild cognitive impairment and dementia in the elderly

INTRODUCTION: a significant percentage of the elderly population suffers from mild cognitive impairment or dementia, affecting memory and learning functions. OBJECTIVES: to synthesise the evidence on supplementation with immunonutrients containing antioxidants and its effect on the progression of mild cognitive impairment and dementia. MATERIALS AND METHODS: a scoping review was conducted in MEDLINE (PubMed) Embase and Web of Sciencie (WoS), developing a search strategy combining MeSH terms, free keywords, Boolean operators, and filters. The strategy was based on three search equations (supplementation; immunonutrient components; dementia and cognitive impairment). Findings were reported according to PRISMA ScR. RESULTS: a total of 803 references were compiled, of which 12 were selected (n = 8 randomised clinical trials, n = 3 cohort studies and n = 1 open clinical trial). Significant evidence was observed for vitamins E (α-tocopherol, γ-tocopherol, δ-tocopherol and β-tocopherol), A and D3, folic acid, vitamin B12, carotenoids (lutein, zeaxanthin, meso-zeaxanthin and xanthophyll) and omega-3 polyunsaturated fatty acids (docosahexaenoic acid and eicosapentaenoic acid) and omega-6 polyunsaturated fatty acids (gamma-linolenic acid and linoleic acid). The synergy between B9 (folic acid) and B12 had the most significant effects on cognitive improvement, together with supplementation with omega-3 fatty acids (DHA and EPA). The results obtained after supplementation with several antioxidant immunonutrients vary depending on the initial diagnosis of the participants, with the greatest benefits found in individuals diagnosed with cognitive impairment or mild dementia. CONCLUSIONS: current evidence suggests that immunonutrition could be a promising strategy for maintaining brain health and delaying cognitive decline, although clinical trials are needed to confirm these findings.