Vitamin E and cognitive function: A systematic review of clinical evidence

Cognitive impairment is a hallmark of Alzheimer's disease (AD) and represents a challenge for patients and the health care system worldwide. Current pharmacological treatments of AD focus on addressing symptom management, with limited options to prevent or slow cognitive decline. Vitamin E is one of the suggested antioxidants that has a protective role against cognitive impairment (CI). We aimed to systematically review the literature and evaluate the evidence on the role of vitamin E in cognitive function. Four databases, PubMed, Scopus, Web of Science, and Cochrane Library, were searched for clinical studies published between 2012 and 2022. Study selection and data extraction followed PRISMA guidelines, and eligible studies were classified into 3 classes: vitamin E supplements, dietary vitamin E, and multivitamins containing vitamin E. A total of 43 clinical studies involving 80,488 participants were identified. Of them, one on vitamin E supplement, 18 on dietary vitamin E, and 24 on multivitamins containing vitamin E. Overall, this systematic review suggest that vitamin E, particularly when consumed as a dietary component or multivitamin supplement with other vitamins, herbs, and minerals, is associated with a protective effect against cognitive impairment, probably mediated by the synergistic effect of other components of the dietary pattern or the multivitamin supplement. However, clinical studies specifically investigating the role of tocotrienols and non-α-tocopherols isoforms, or their combinations in CI, remain limited and warrant further investigations.