Carmel R
Ann Intern Med. 1978 May;88(5):647-9. doi: 10.7326/0003-4819-88-5-647.
Dietary deficiency of vitamin B-12 has been reported, yet most people ingesting vitamin-B12-deficient diets even for many years appear to achieve a balance that does not lead to overt signs and symptoms of deficiency. I present the case of a vegan of 25 years' duration who developed severe neurologic abnormalities due to vitamin-B12 deficiency. His diet provided 1.2 microgram of vitamin B12 daily at most. Despite normal Schilling test findings, he absorbed subnormal amounts of vitamin B12 given with ovalbumin. This poor absorption appeared to be related to his gastritis, achlorhydria, and subnormal intrinsic-factor secretion. Probably, vitamin-B12 deficiency in this patient resulted from both dietary restriction and the subtle malabsorption, neither of which would have sufficed alone to produce the clinical problem. Possibly such malabsorption may also be present in many of those vegans developing overt vitamin-B12 deficiency in whom Schilling test findings have been normal.
已有关于维生素B12膳食缺乏的报道，但大多数摄入维生素B12缺乏饮食多年的人似乎能达到一种平衡，不会出现明显的缺乏体征和症状。我介绍了一例长达25年的纯素食者因维生素B12缺乏而出现严重神经异常的病例。他的饮食每天最多提供1.2微克维生素B12。尽管希林试验结果正常，但他对与卵清蛋白一起给予的维生素B12吸收量低于正常水平。这种吸收不良似乎与他的胃炎、胃酸缺乏和内因子分泌低于正常水平有关。该患者的维生素B12缺乏可能是由于饮食限制和轻微的吸收不良共同导致的，单独任何一个因素都不足以引发临床问题。在许多希林试验结果正常但出现明显维生素B12缺乏的纯素食者中，可能也存在这种吸收不良的情况。
