Delport R
Department of Chemical Pathology, Faculty of Medicine, University of Pretoria, PO Box 2034, Pretoria 0001, South Africa.
J Nutr Health Aging. 2000;4(4):195-6.
Vitamin B12 and to a lesser extent folate deficiencies have been associated with dementias. Both these vitamins are determinants of plasma total homocysteine concentrations. In this review the frequency distributions of plasma vitamin B12, folate and homocysteine in South African males (# 51 yrs and > 51 yrs) illustrate the lower vitamin B12 levels in older subjects, and the shift toward elevated homocysteine concentrations in elderly people. Vitamin B12 deficiency appears to be associated with neuropsychiatric disorders, including dementias, but no causal relationship based on biochemical evidence has so far been established. Supplementation with vitamin B12 improves some neurological abnormalities and reverses only mild dementia of recent onset, but does not slow the progression of dementia. Elevated homocysteine levels appears to affect cognitive function, as measured by spatial copying skills and visual event-related potentials. Measurement of plasma homocysteine may help identify individuals with vitamin deficiencies and hyperhomocysteinemia. The relation between B-vitamins, homocysteine and dementia needs to explored further before vitamin supplementation is advocated to prevent or reverse neuropsychiatric disorders.
维生素B12缺乏以及程度较轻的叶酸缺乏与痴呆症有关。这两种维生素都是血浆总同型半胱氨酸浓度的决定因素。在本综述中，南非男性（51岁及以上和51岁以上）血浆维生素B12、叶酸和同型半胱氨酸的频率分布表明，老年受试者的维生素B12水平较低，且老年人的同型半胱氨酸浓度有升高的趋势。维生素B12缺乏似乎与包括痴呆症在内的神经精神疾病有关，但迄今为止，尚未根据生化证据确立因果关系。补充维生素B12可改善一些神经异常情况，仅能逆转近期发生的轻度痴呆症，但无法减缓痴呆症的进展。同型半胱氨酸水平升高似乎会影响认知功能，这可通过空间复制技能和视觉事件相关电位来衡量。检测血浆同型半胱氨酸可能有助于识别维生素缺乏和高同型半胱氨酸血症患者。在提倡补充维生素以预防或逆转神经精神疾病之前，需要进一步探讨B族维生素、同型半胱氨酸与痴呆症之间的关系。
