Effects of folic acid, alone or in combination with other nutrients on Hcy level and cognitive function in older people: a systematic review

Abstract

Abstract Background Homocysteine is a high-risk factor for cognitive decline, and supplementing with B vitamins such as folic acid can lower homocysteine levels. However, current clinical research results are inconsistent, and the effects of B vitamins on homocysteine levels and cognitive function in older people are inconsistent. Methods Systematic searches were conducted in five databases including PubMed, Embase, the Cochrane Library, Web of Science, and Cumulative Index to Nursing and Allied Health Literature (CINAHL), from inception to March 1, 2023. Randomized controlled trials investigating the effects of folic acid alone or in combination with other nutrients on cognitive function in patients with cognitive disorders were included. The quality of the literature was evaluated using RevMan 5.4. Results 17 articles were reviewed, with 6 focusing on the effects of folic acid alone and 11 examining folic acid in combination with other nutrients. folic acid dosages ranged from 400 µg to 5 mg, and intervention durations varied from 4 weeks to 3 years. The study included 3,100 individuals, aged 60 to 83.2 years, with a relatively equal gender distribution (approximately 51.82%). Conclusion Most studies have shown that folic acid alone or in combination with other nutrients can effectively improve cognitive function in patients with mild cognitive impairment. For patients with Alzheimer's disease and dementia, folic acid alone or in combination with other nutrients can reduce the level of homocysteine, but the improvement in cognitive function is not significant. In healthy older people, high baseline homocysteine levels (> 11.3 µmol/L) and good ω-3 fatty acid status (> 590 µmol/L) can enhance the improvement effect of B vitamins on cognitive function. This trial has been registered on PROSPERO as CRD42023408576.