Malinow M R, Duell P B, Hess D L, Anderson P H, Kruger W D, Phillipson B E, Gluckman R A, Block P C, Upson B M
Division of Pathobiology and Immunology, Oregon Regional Primate Research Center, Beaverton 97006-3448, USA.
N Engl J Med. 1998 Apr 9;338(15):1009-15. doi: 10.1056/NEJM199804093381501.
The Food and Drug Administration (FDA) has recommended that cereal-grain products be fortified with folic acid to prevent congenital neural-tube defects. Since folic acid supplementation reduces levels of plasma homocyst(e)ine, or plasma total homocysteine, which are frequently elevated in arterial occlusive disease, we hypothesized that folic acid fortification might reduce plasma homocyst(e)ine levels.
To test this hypothesis, we assessed the effects of breakfast cereals fortified with three levels of folic acid, and also containing the recommended dietary allowances of vitamins B6 and B12, in a randomized, double-blind, placebo-controlled, crossover trial in 75 men and women with coronary artery disease.
Plasma folic acid increased and plasma homocyst(e)ine decreased proportionately with the folic acid content of the breakfast cereal. Cereal providing 127 microg of folic acid daily, approximating the increased daily intake that may result from the FDA's enrichment policy, increased plasma folic acid by 31 percent (P=0.045) but decreased plasma homocyst(e)ine by only 3.7 percent (P= 0.24). However, cereals providing 499 and 665 microg of folic acid daily increased plasma folic acid by 64.8 percent (P<0.001) and 105.7 percent (P=0.001), respectively, and decreased plasma homocyst(e)ine by 11.0 percent (P<0.001) and 14.0 percent (P=0.001), respectively.
Cereal fortified with folic acid has the potential to increase plasma folic acid levels and reduce plasma homocyst(e)ine levels. Further clinical trials are required to determine whether folic acid fortification may prevent vascular disease. Until then, our results suggest that folic acid fortification at levels higher than that recommended by the FDA may be warranted.
美国食品药品监督管理局(FDA)建议谷物产品添加叶酸以预防先天性神经管缺陷。由于补充叶酸可降低血浆同型半胱氨酸或血浆总同型半胱氨酸水平,而这两种物质在动脉闭塞性疾病中常升高,我们推测叶酸强化可能会降低血浆同型半胱氨酸水平。
为验证这一假设,我们在一项随机、双盲、安慰剂对照、交叉试验中,评估了添加三种叶酸水平且含有推荐膳食摄入量的维生素B6和B12的早餐谷物对75名冠心病男女患者的影响。
血浆叶酸随着早餐谷物中叶酸含量的增加而升高,血浆同型半胱氨酸则相应降低。每日提供127微克叶酸的谷物,接近FDA强化政策可能导致的每日摄入量增加量,使血浆叶酸增加了31%(P = 0.045),但血浆同型半胱氨酸仅降低了3.7%(P = 0.24)。然而,每日提供499微克和665微克叶酸的谷物分别使血浆叶酸增加了64.8%(P < 0.001)和105.7%(P = 0.001),并分别使血浆同型半胱氨酸降低了11.0%(P < 0.001)和14.0%(P = 0.001)。
添加叶酸的谷物有潜力提高血浆叶酸水平并降低血浆同型半胱氨酸水平。需要进一步的临床试验来确定叶酸强化是否可预防血管疾病。在此之前,我们的结果表明可能有必要采用高于FDA推荐水平的叶酸强化措施。