科学家发现维生素 B12 摄入量指南存在重大问题，您的大脑可能面临风险

　　

即使是“正常”水平的维生素 B12 也可能不足以保护衰老的大脑。

加州大学旧金山分校的研究人员发现，维生素 B12 含量较低但从技术上讲仍然正常的老年人，其处理速度较慢，白质损伤较多，认知能力较弱。

当“正常”维生素 B12 可能不够时

维生素B12是DNA 、红细胞和神经组织合成所必需的，满足每日标准维生素B12需求量可能无法为大脑提供足够的保护，尤其是在老年人中。事实上，即使维生素B12的摄入量处于“正常”范围内，也可能增加认知问题的风险。

加州大学旧金山分校的研究人员对健康的老年人进行了研究，发现维生素B12水平较低的参与者即使仍然被认为是正常的，也表现出神经和认知能力的缺陷。与维生素B12水平较高的人相比，这些人的大脑白质（负责大脑不同区域之间沟通的神经纤维网络）受损更严重，在认知速度和视觉处理能力的测试中得分也较低。

该研究发表在《神经病学年鉴》上。

重新思考维生素B12指南

加州大学旧金山分校神经病学和眼科学系以及威尔神经科学研究所的资深作者 Ari J. Green 医学博士表示，研究结果引发了人们对当前 B12 建议是否足够的担忧，并表明可能需要修改指南。

“之前对维生素B12健康摄入量进行定义的研究，可能忽略了维生素B12水平过高或过低的细微功能性表现，这些表现可能会影响人体，但不会引发明显的症状，”格林说道，并指出维生素B12的明显缺乏通常与某种类型的贫血有关。“重新审视维生素B12缺乏症的定义，将功能性生物标志物纳入其中，或许可以更早地干预并预防认知能力下降。”

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 维生素B12含量低、思维迟缓和脑损伤
 <p>In the study, researchers enrolled 231 healthy participants without dementia or mild cognitive impairment, whose average age was 71. They were recruited through the Brain Aging Network for Cognitive Health (BrANCH) study at UCSF.p>
 <p>Their blood B12 amounts averaged 414.8 pmol/L, well above the U.S. minimum of 148 pmol/L. Adjusted for factors like age, sex, education and cardiovascular risks, researchers looked at the biologically active component of B12, which provides a more accurate measure of the amount of the vitamin that the body can utilize. In cognitive testing, participants with lower active B12 were found to have slower processing speed, relating to subtle cognitive decline. Its impact was amplified by older age. They also showed significant delays responding to visual stimuli, indicating slower visual processing speeds and general slower brain conductivity.p>
 <p>MRIs revealed a higher volume of lesions in the participants’ white matter, which may be associated with cognitive decline, dementia, or stroke.p>
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  Implications for Prevention and Future Research
  <p>While the study volunteers were older adults, who may have a specific vulnerability to lower levels of B12, co-first author Alexandra Beaudry-Richard, MSc, said that these lower levels could “impact cognition to a greater extent than what we previously thought, and may affect a much larger proportion of the population than we realize.” Beaudry-Richard is currently completing her doctorate in research and medicine at the UCSF Department of Neurology and the Department of Microbiology and Immunology at the University of Ottawa.p>
  <p>“In addition to redefining B12 deficiency, clinicians should consider supplementation in older patients with neurological symptoms even if their levels are within normal limits,” she said. “Ultimately, we need to invest in more research about the underlying biology of B12 insufficiency, since it may be a preventable cause of cognitive decline.”p>
  <p><em>自2025年2月发表以来，该研究结果引发了研究人员和临床医生的广泛讨论。多项评论强化了维生素B12水平偏低与轻微神经损伤之间的联系，并指出目前的指导方针可能低估了大脑的真正需求。em>p>
  <p><em>评论人士呼吁提高维生素B12缺乏的临界值，并转向测量生物活性维生素B12（全转钴胺素）而非血清总水平，因为即使是“健康”水平也可能使老年人容易出现认知能力下降和白质损伤。早期报告还强调了活性维生素B12水平低与神经退行性标志物（例如tau蛋白）升高之间的关联，这强化了重新定义充足维生素B12摄入量的理由。em>p>
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