Campbell N R
Department of Medicine, Faculty of Medicine, University of Calgary, Alberta.
Arch Intern Med. 1996;156(15):1638-44.
Periconceptual use of folic acid supplements by women is effective in preventing neural tube defects in the fetus. Folic acid supplements also may prevent atherosclerosis and some malignant neoplasms. Nevertheless, safety concerns have delayed recommendations to increase folic acid consumption by the general population. Among the potential safety issues of folic acid supplementation are (1) difficulty identifying cobalamin deficiency, precipitation of neurologic complications of cobalamin deficiency, and lowering of cobalamin levels; (2) folate neurotoxicity; (3) antagonism of drugs that inhibit folate metabolism; (4) reduced zinc absorption; (5) association with malignant neoplasms; (6) hypersensitivity reactions; and (7) increased susceptibility to malaria. The data that suggest that folic acid supplements are unsafe are weak and consist predominantly of case series and reports. Nevertheless, greater difficulty diagnosing cobalamin deficiency due to "masking" of hematologic abnormalities by folic acid is a potential risk. Strict vegetarians need to be informed that they are at risk of cobalamin deficiency. Physicians need to be aware that routine hematologic indexes have a low sensitivity for cobalamin deficiency, especially in patients who are receiving folic acid supplements. Because no high-quality data exclude specific adverse effects, physicians should be vigilant in identifying detrimental effects when patients increase their consumption of folic acid.
女性在受孕前后使用叶酸补充剂可有效预防胎儿神经管缺陷。叶酸补充剂还可能预防动脉粥样硬化和某些恶性肿瘤。然而，出于安全考虑，针对普通人群增加叶酸摄入量的建议被推迟。叶酸补充的潜在安全问题包括：（1）难以识别钴胺素缺乏、钴胺素缺乏神经并发症的发生以及钴胺素水平降低；（2）叶酸神经毒性；（3）对抑制叶酸代谢药物的拮抗作用；（4）锌吸收减少；（5）与恶性肿瘤的关联；（6）过敏反应；以及（7）对疟疾易感性增加。表明叶酸补充剂不安全的数据较为薄弱，主要包括病例系列和报告。然而，由于叶酸“掩盖”血液学异常而导致更难诊断钴胺素缺乏是一个潜在风险。需要告知严格的素食者他们有钴胺素缺乏的风险。医生需要意识到常规血液学指标对钴胺素缺乏的敏感性较低，尤其是在正在服用叶酸补充剂的患者中。由于没有高质量数据排除特定不良反应，当患者增加叶酸摄入量时，医生应警惕识别有害影响。
