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首页> 外文期刊>International Journal for Vitamin and Nutrition Research: Internationale Zeitschrift fur Vitamin- und Ernahrungsforschung >Studies on vitamin B12 status in the elderly--prophylactic and therapeutic consequences.
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Studies on vitamin B12 status in the elderly--prophylactic and therapeutic consequences.

机译：老年人维生素B12状况的研究-预防和治疗后果。

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摘要

Because of the large liver stores (about 5 mg), low turnover rate (0.143%) and small daily requirement (3 micrograms), vitamin B12 deficiency does not occur under normal circumstances. This is not the case in individuals with chronic inflammatory or trophic changes at vitamin B12 absorption sites. Without supplementation, vitamin B12 deficiency can be expected within 5 years of gastrectomy. Characteristic features of type A gastritis are hyposecretion and mucosal atrophy in the fundus and body of the stomach, with absent intrinsic factor. In the small intestine, active and/or passive absorption is impaired by extensive ileal resection, exocrine pancreatic insufficiency and chronic inflammatory disorders such as Crohn's disease. Definitive plasma concentrations cannot be quoted for vitamin B12 deficiency. Dietary habits, subjective symptoms, hematological laboratory results, function tests and gastrointestinal endoscopic and histological findings must all be taken into account in the diagnosis. Modern diagnostic parameters, such as methylmalonic acid and homocysteine serum assays, are useful for achieving early diagnosis and hence optimal treatment. With their assured availability, parenteral vitamin B12 preparations remain the treatment of choice. Results from vitamin B12 bioavailability studies in healthy subjects suggest that > 300 micrograms probably suffices as an oral maintenance dose after parenteral loading. Further well-documented cases are needed in order to establish whether these doses are adequate in malabsorption syndromes and gastrointestinal diseases. Various case reports indicate the value of prophylactic and therapeutic oral vitamin B12 administration, especially in disorders of homocysteine metabolism, a substance postulated as a further important risk factor for atherosclerosis.
机译：由于肝脏储存量大（约5 mg），周转率低（0.143％）和每日需求量小（3微克），因此在正常情况下不会发生维生素B12缺乏症。在维生素B12吸收位点发生慢性炎症或营养变化的个体则不是这种情况。如果不补充，可以在胃切除术后5年内预期维生素B12缺乏。 A型胃炎的特征是胃底和胃体分泌不足和粘膜萎缩，而缺乏内在因素。在小肠中，广泛的回肠切除术，外分泌胰腺功能不全和慢性炎症性疾病（如克罗恩氏病）会损害主动和/或被动吸收。不能引用确定的血浆浓度来补充维生素B12缺乏症。诊断时必须考虑饮食习惯，主观症状，血液学检查结果，功能检查以及胃肠道内镜和组织学检查结果。现代诊断参数（例如甲基丙二酸和高半胱氨酸血清检测）可用于实现早期诊断并因此获得最佳治疗。肠胃外维生素B12制剂可确保其可用性，因此仍然是治疗的选择。在健康受试者中进行的维生素B12生物利用度研究的结果表明，肠胃外负荷后，口服维持剂量> 300微克就足够了。为了确定这些剂量在吸收不良综合征和胃肠道疾病中是否足够，还需要更多有据可查的病例。各种病例报告都表明口服和预防性口服维生素B12的价值，尤其是在同型半胱氨酸代谢异常中的价值，该物质被认为是导致动脉粥样硬化的另一重要危险因素。

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