Cancer Epidemiology Unit, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.
Eur J Clin Nutr. 2010 Sep;64(9):933-9. doi: 10.1038/ejcn.2010.142. Epub 2010 Jul 21.
BACKGROUND/OBJECTIVES: Vegans, and to a lesser extent vegetarians, have low average circulating concentrations of vitamin B12; however, the relation between factors such as age or time on these diets and vitamin B12 concentrations is not clear. The objectives of this study were to investigate differences in serum vitamin B12 and folate concentrations between omnivores, vegetarians and vegans and to ascertain whether vitamin B12 concentrations differed by age and time on the diet.
SUBJECTS/METHODS: A cross-sectional analysis involving 689 men (226 omnivores, 231 vegetarians and 232 vegans) from the European Prospective Investigation into Cancer and Nutrition Oxford cohort.
Mean serum vitamin B12 was highest among omnivores (281, 95% CI: 270-292 pmol/l), intermediate among vegetarians (182, 95% CI: 175-189 pmol/l) and lowest among vegans (122, 95% CI: 117-127 pmol/l). In all, 52% of vegans, 7% of vegetarians and one omnivore were classified as vitamin B12 deficient (defined as serum vitamin B12 <118 pmol/l). There was no significant association between age or duration of adherence to a vegetarian or a vegan diet and serum vitamin B12. In contrast, folate concentrations were highest among vegans, intermediate among vegetarians and lowest among omnivores, but only two men (both omnivores) were categorized as folate deficient (defined as serum folate <6.3 nmol/l).
Vegans have lower vitamin B12 concentrations, but higher folate concentrations, than vegetarians and omnivores. Half of the vegans were categorized as vitamin B12 deficient and would be expected to have a higher risk of developing clinical symptoms related to vitamin B12 deficiency.
背景/目的：素食者（尤其是严格素食者）的平均循环维生素 B12 浓度较低；然而，年龄或这些饮食的时间等因素与维生素 B12 浓度之间的关系尚不清楚。本研究的目的是调查杂食者、素食者和严格素食者之间血清维生素 B12 和叶酸浓度的差异，并确定维生素 B12 浓度是否因年龄和饮食时间而异。
受试者/方法：这是一项涉及欧洲癌症前瞻性调查和营养牛津队列中的 689 名男性（226 名杂食者、231 名素食者和 232 名严格素食者）的横断面分析。
杂食者的血清维生素 B12 平均值最高（281，95%CI：270-292 pmol/l），素食者居中（182，95%CI：175-189 pmol/l），严格素食者最低（122，95%CI：117-127 pmol/l）。共有 52%的严格素食者、7%的素食者和 1 名杂食者被归类为维生素 B12 缺乏症（定义为血清维生素 B12 <118 pmol/l）。血清维生素 B12 与年龄或素食或严格素食饮食的持续时间之间没有显著关联。相比之下，叶酸浓度在严格素食者中最高，在素食者中居中，在杂食者中最低，但只有两名男性（均为杂食者）被归类为叶酸缺乏症（定义为血清叶酸<6.3 nmol/l）。
严格素食者的维生素 B12 浓度低于素食者，但高于杂食者，而且有一半的严格素食者被归类为维生素 B12 缺乏症，预计他们患与维生素 B12 缺乏相关的临床症状的风险更高。
