谷胱甘肽（2）

谷胱甘肽

谷胱甘肽的功能

谷胱甘肽是由三种氨基酸组成的蛋白质，它们是：半胱氨酸、谷氨酸和氨基乙酸。谷胱甘肽在解毒过程中起到重要作用，它与毒素如重金属、溶剂和杀虫剂相结合，然后将它们转化成可以从尿液或胆汁中排出的物质。谷胱甘肽还是重要的抗氧化物。以前的研究认为，每天从水果和生的蔬菜中摄入的谷胱甘肽可以预防一些癌症。^{[1 2]}谷胱甘肽在试管试验^[3]和动物实验^[4]中也能抑制癌症。以前的研究还发现高水平的谷胱甘肽与老年人的健康有关。^[5]

谷胱甘肽补充剂可被老鼠有效吸收。^{[6 7]}可是，同样的形式却不能被人类吸收。例如，给予7位健康人单一服用3000毫克的谷胱甘肽却不能增加血液中谷胱甘肽的水平。^[8]这一研究的作者认为单一口服3000毫克的谷胱甘肽不易提高血液循环中的谷胱甘肽水平。在老鼠中能更有效的吸收谷胱甘肽是因为老鼠的胃肠道不同于人类，人类的胃肠道内含有大量的酶（γ-谷氨酰转肽酶）降解谷胱甘肽。以前的证据表明谷胱甘肽在舌下含服时能很好的吸收。^[9]

一些研究者认为补充剂比口服谷胱甘肽能更有效的升高血液中谷胱甘肽的水平。例如，在某项试验中，健康人每天服用500毫克的维生素C仅仅两周就可以升高血液中50%的谷胱甘肽水平。^[10]这与维生素C帮助机体合成谷胱甘肽有关。另外，其他营养补充剂如α-硫辛酸^[11]、谷氨酰胺^[12]、甲硫氨酸^[13]，S-腺苷甲硫氨酸^[14]和乳清蛋白^[15]、维生素B6、核黄素和硒也可以帮助提高谷胱甘肽水平。其具体机理目前还不十分清楚。

静脉或肌肉注射谷胱甘肽对于预防手术期间血液凝固有一定作用，^[16]它还能降低化疗药物的副作用和提高其疗效（尤其是用顺铂治疗女性的卵巢癌）、^{[17 18]}治疗帕金森氏病、^[19]降低糖尿病患者的血压^[20]以及增加男性精子数量等^{[21 22]}。谷胱甘肽滴鼻剂还能降低慢性鼻炎的症状^[23]。到目前为止还不十分清楚口服谷胱甘肽是否有效。在一个对8例肝癌患者进行的口服谷胱甘肽试验中发现每天口服5000毫克对于女性有中度的疗效，但对于男性却没有效果。^[24]

以前的一项未公开的对8例结肠癌患者进行的试验发现口服谷胱甘肽具有抗癌活性。^[25]然而，因为存在口服谷胱甘肽是否能吸收的问题，所以一些医生质疑口服谷胱甘肽是否比其他形式效果差或根本就没有效果。

谷胱甘肽的分布

饮食中发现新鲜的和冷冻的水果、蔬菜、鱼和肉类^[26]、芦笋、鳄梨和胡桃含有丰富的谷胱甘肽。

谷胱甘肽已经被应用于与以下疾病的治疗中。（以下所有信息适用于个体化健康情况）：

哪些人可能会缺乏谷胱甘肽？

谷胱甘肽缺乏会因为机体对谷胱甘肽的需求增加、合成所需的氨基酸缺乏或因疾病导致谷胱甘肽合成减少。^[27]与谷胱甘肽缺乏相关的疾病有糖尿病、精子数量降低、肝脏疾病、白内障、艾滋病、呼吸抑制综合征、癌症和特发性肺纤维化。吸烟者也会导致谷胱甘肽的减少，因为它会增加对谷胱甘肽的利用率。

一般需要多少谷胱甘肽？

前对于谷胱甘肽补充剂有多大作用还不十分清楚，尽管对于吸入、静脉注射和肌肉注射谷胱甘肽已经能治疗一些疾病。有证据表明机体缺乏谷胱甘肽时需静脉、肌肉或吸入补充谷胱甘肽，这些需在医生的指导下进行。所有卵巢癌的病人正在服用顺铂时应该在医生的指导下静脉给予谷胱甘肽。

是否有副作用和药物相互作用？

目前关于口服补充谷胱甘肽还没发现任何副作用。

一些药物会与谷胱甘肽发生相互作用，参见药物间相互作用章节。

参考文献

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