Effects and reporting quality of the vitamin supplementation on cognitive function in older adults with Alzheimer's disease ‒ A systematic review.

Abstract

Introduction: Background: evidence supporting the effectiveness of vitamin supplementation on cognitive function in older adults with Alzheimer's disease (AD) is limited, and the reporting quality of existing research is often overlooked. Objectives: to a) evaluate the effectiveness of vitamin supplementation on cognitive function in older adults with AD; b) describe the characteristics of supplementation protocols; and c) assess the reporting quality of these interventions. Methods: a systematic search of seven databases was conducted for randomized controlled trials (RCTs) up to February 2026. Included studies involved vitamin supplementation for patients with AD and assessed cognitive outcomes. The risk of bias and reporting quality were evaluated. Results: seventeen RCTs (n = 2,478 participants) were included. While eight studies reported some cognitive improvements or stabilization with vitamin B3, D, E, folic acid or specialized multi-nutrient formulations, nine found no significant benefit. A high risk of bias was identified in seven studies, while only five were rated as low risk. The median TIDieR score of 10/12 indicates a good description of the vitamin supplementation protocols. Conclusions: the current evidence for vitamin supplementation in older adults with AD is inconclusive. While some protocols show potential for stabilizing or improving cognitive domains, results are compromised by methodological heterogeneity and a high risk of bias. Future research must focus on enhancing methodological quality and achieving greater homogeneity in vitamin supplementation prescription and dosing to ensure robust clinical evidence for patients with AD.