Department of Obstetrics and Gynaecology, University Hospital Nijmegen St Radboud, The Netherlands.
Nutr Res Rev. 2001 Dec;14(2):267-94. doi: 10.1079/NRR200126.
Folic acid is important because supplementation around the time of conception has been proven to lower the risk of having offspring with a neural-tube defect. Furthermore, both dietary folate and folic acid decrease plasma total homocysteine concentrations. Elevated plasma homocysteine concentrations are considered to be an independent risk factor for cardiovascular disease. The aim of the present review is to give an overview of factors influencing bioavailability and bioefficacy (the proportion of ingested nutrient converted to its active form) of food folate and folic acid, and to discuss the functional bioefficacy of folate and folic acid in decreasing plasma homocysteine concentrations. We use the mnemonic SLAMENGHI to group factors influencing bioavailability and bioefficacy: Species of folate; Linkage at molecular level; Amount of folate and folic acid consumed; Matrix; Effect modifiers; Nutrient status; Genetic factors; Host-related factors; mathematical Interactions between the various factors. Bioefficacy of folate from some foods is 50 % that of folic acid. This factor is most probably explained by the matrix factors, encapsulation and binding. However, often such effects cannot be distinguished from factors such as species, chain length of folate in food, effect modifiers and the amount of folate consumed in a meal. Folic acid provided as a supplement is well absorbed. However, the homocysteine-lowering capacity of doses of folic acid >500 mug is limited. It is unclear whether unmetabolised folic acid poses health risks. This factor is of importance, because food fortification is now implemented in many countries and folic acid supplements are freely available. In particular circumstances host-related factors, such as gastrointestinal illness and pH of the jejunum, can influence bioavailability. Genetic factors also deserve attention for future research, because polymorphisms may influence folate bioavailability.
叶酸很重要，因为在受孕前后补充叶酸已被证明可以降低后代神经管缺陷的风险。此外，膳食叶酸和叶酸都可以降低血浆总同型半胱氨酸浓度。升高的血浆同型半胱氨酸浓度被认为是心血管疾病的一个独立危险因素。本综述的目的是概述影响食物叶酸和叶酸生物利用度和生物效价（摄入的营养素转化为其活性形式的比例）的因素，并讨论叶酸和叶酸降低血浆同型半胱氨酸浓度的功能生物效价。我们使用 SLAMENGHI 这个首字母缩写词来分组影响生物利用度和生物效价的因素：叶酸的种类；分子水平上的连接；叶酸和叶酸的摄入量；基质；效应修饰剂；营养状况；遗传因素；宿主相关因素；各种因素之间的数学相互作用。一些食物中的叶酸的生物效价是叶酸的 50%。这一因素很可能是由基质因素、包封和结合来解释的。然而，通常情况下，这些影响无法与种类、食物中叶酸的链长、效应修饰剂和一餐中叶酸的摄入量等因素区分开来。作为补充剂提供的叶酸吸收良好。然而，叶酸剂量大于 500 微克时，降低同型半胱氨酸的能力是有限的。尚未代谢的叶酸是否会带来健康风险尚不清楚。这一因素很重要，因为现在许多国家都在实施食品强化，叶酸补充剂也可以自由获得。在特定情况下，宿主相关因素，如胃肠道疾病和空肠的 pH 值，会影响生物利用度。遗传因素也值得未来的研究关注，因为多态性可能会影响叶酸的生物利用度。
