免疫功能低下的营养策略：维生素、益生菌、紫锥菊

目 录

1. 简介
   

2. 一览表

3. 症状

4. 治疗

5. 饮食习惯的改变 

6. 生活方式的改变

7. 补充剂

8. 相关草药

9. 整体疗法

10. 参考文献

人体的免疫系统像一张复杂的大网，由一些特殊的组织、器官、细胞和化学分子组成。淋巴结、脾脏、骨髓、胸腺、扁桃体都是这张大网的一部分，淋巴细胞（白细胞中的一种）、抗体和干扰素也是，在其中扮演着重要的角色。

免疫系统对人体的保护可以分为两种：先天性免疫和获得性免疫。先天性免疫作为第一道屏障，在人出生的时候就起到了防御微生物的作用。皮肤、各种粘膜分泌物和胃内的酸性环境都是先天性免疫的例子，它们同样起到屏障作用，防止那些有害微生物侵袭身体中比较脆弱易感的组织。

获得性免疫是抗感染的第二道屏障。它不是与生俱来的，而是出生后通过其它一些方式获得的，比如通过我们常说的注射疫苗，还有被微生物感染恢复后机体便对其产生了免疫力。获得性免疫系统能够对所有入侵者保持一种记忆，因此再次被这种入侵者攻击时，机体能够很容易察觉并且动员反击。这也是尽管我们经常接触麻疹的病原体，但一生中通常只会得一次麻疹的原因。然而不幸的是，自然界还存在着某些微生物，比如导致普通感冒的病毒，它们能够通过自我掩饰而一次次的躲避免疫系统的监视，因而人们会反复患普通感冒。

免疫功能低下的辅助疗法

免疫功能低下的症状

免疫功能下降的症状包括：经常反复发生感冒或流感，曾经治愈的寄生虫感染又复发，原本的一些轻微感染进展为严重的机会感染（机会感染，是指由一些特定的微生物所引起的感染，包括弓形虫、隐球菌、巨细胞病毒等；在免疫系统正常工作的情况下，这些微生物是不会造成感染的），甚至癌症。

药物治疗

处方药物治疗包括预防性抗生素，以及免疫促进药物如干扰素（Roferon-A^®, Intron A, Infergen^®）和白介素（Proleukin^®）。

针对免疫力低下的治疗也包括注射各种疫苗，如流感疫苗、肺炎球菌疫苗、肝炎疫苗、破伤风疫苗或者其他感染性微生物疫苗，同时注意减少接触病原微生物。

可能有益的饮食习惯

糖分

各种形式的糖分都会影响白细胞对抗细菌的能力。^[1,2] 动物实验表明，蔗糖含量高的饮食对免疫功能的某些部分有损害。^[3,4] 这些研究结果对于人体康感染方面的重要性目前尚不清楚。

酒精

酒精摄入，包括间断中等量饮酒，都会影响多种免疫防御功能。^[5,6]  酒精的免疫抑制作用可能作为用来解释酒精摄入与某些癌症^[7]或感染^[8,9]相关性的一种机制。不过，一些研究证实，在不吸烟的年轻人中，中度饮酒（每天饮酒3到4次）可使发生上呼吸道感染的危险不变^[10]或下降^[11]。

脂肪

脂肪对免疫系统的影响很复杂，目前仅有部分被人们所认识。总饮食摄入脂肪过多损害免疫应答，但是某些种类的脂肪是无害甚至有益的。^[12] 例如，橄榄油中的单不饱和脂肪，在合理膳食摄入的情况下，对人体的免疫系统是无害的。^[13]

Ω-3脂肪酸

对Ω-3脂肪酸进行的一些研究结论并不一致。鱼、鱼油以及亚麻仁油中富含Ω-3脂肪酸。医院内给重症病人使用的含有Ω-3脂肪酸的流质食品能够增强免疫功能，减少感染。^[14,15]但是，在一个健康人群的对照实验中，低脂饮食增强或维持免疫功能，但是在饮食中加入鱼类以增加Ω-3脂肪酸摄入时，免疫功能被明显抑制。^[16]

维生素E

给健康年轻人补充DHA（鱼油中的Ω-3脂肪酸）会降低诸如NK细胞等免疫细胞的活性，并且在试管中抑制某些炎症反应。^[17]  DHA的抗炎作用在治疗自身免疫疾病中有价值，但是同时也可能增加感染的危险。其他研究表明，氧化损伤的增加可能是鱼油对免疫系统负性作用的原因，增加抗氧化剂的摄入，比如维生素E，能够纠正此问题。^[18]

Ω-6脂肪酸

像Ω-3脂肪酸一样，Ω-6脂肪酸（存在于植物油中）对人类免疫系统也有双重作用。在低脂饮食中增加Ω-6脂肪酸并不损害免疫功能。^[19]但是，有人报道Ω-6脂肪酸含量高的饮食抑制免疫功能。^[20,21]

总的来说，含有中等量但不饱和脂肪酸的低脂饮食至少对免疫系统有轻度抑制作用，有些情况下这种轻度抑制是有好处的。有关于是否在饮食中添加高含量Ω-3或Ω-6脂肪酸的问题仍有待于进一步研究。

益菌群

许多动物研究和人类研究都已经证明，含有乳酸杆菌活菌及其他有益菌群的食品酸奶有刺激免疫的作用。在人体中观察到有益菌群的作用包括增加几种白细胞的活性。一些人体研究表明，摄入含有活菌群的酸奶与几种免疫相关疾病发病率下降有关，包括癌症、胃肠道感染和一些过敏反应。^[22]

可能有益的生活方式

肥胖

过度消瘦和过度肥胖都与免疫应答受损相关。^[23]一些研究表明，肥胖会增加感染发生的几率，至少对于住院病人来说。^[24]但是，在轻到中度肥胖而其他健康的人群中并不存在这样的影响，而且通过饮食限制进行减肥实际上对免疫系统有害。^[25]体重超重和减肥食品对人体的有害影响可以通过规律的有氧锻炼而抵消。^[26,27]

锻炼

锻炼对免疫功能的影响取决于许多因素，包括锻炼的频率和强度。^[28]规律的中度活动量锻炼能产生有益作用，至少对免疫系统的某些方面有益，并且能够减少上呼吸道感染的几率。但是，高强度长时间的锻炼，例如跑马拉松或过度练习，在短时期内实际上增加感染的发生。^[29]中度锻炼对免疫系统有益处也部分解释了经常锻炼的人群对癌症的易感性明显下降。^[30]

可能有益的营养补充剂

复合型维生素-矿物质配方

大多数^[31,32]双盲试验——但不是所有的^[33]——证实，多种维生素和矿物质搭配摄入的老年人有更好的免疫功能，感染几率也更低。一个双盲试验表明，每天补充100毫克硒和20毫克锌，不管加不加维生素C、维生素E或者β胡萝卜素，都能够降低老年人的感染率，而仅补充维生素不补充矿物质则无效。^[34]双盲试验还发现，烧伤患者补充微量矿物质后感染发生减少。^[35]这些研究表明，对于增加老年人的免疫力和减少感染，微量矿物质可能是最重要的微营养物质。

维生素E

维生素E在老年人可在一定程度上增加免疫细胞活性。^[36]双盲试验表明，每天200国际单位与更低用量（每天60国际单位）或更高用量（每天600国际单位）相比，作用更加明显。^[37]一些研究指出，每天摄入量低于200国际单位时对免疫功能没有作用。^[38]

β胡萝卜素和类胡萝卜

动物实验和人体试验表明，β胡萝卜素和其他类胡萝卜素除了作为维生素A的前体物质之外，还能够使免疫细胞数量和活性增加。^[39,40]安慰剂对照实验显示，给健康人补充β胡萝卜素，每天25,000-100,000国际单位，能产生一些有益作用，使某些白细胞数量增加，加强抗癌的免疫功能。^[41,42]

在老年人中进行的双盲试验显示，每天补充40,000-150,000国际单位的β胡萝卜素能增加NK细胞活性^[43]，但对其他免疫功能没有影响。^[44]

对照实验发现，每天50,000国际单位β胡萝卜素能够增加结肠癌患者的免疫功能，但在结肠癌前状态患者则无此作用。^[45]β胡萝卜素还能预防暴露于紫外线导致的免疫抑制。^[46]β胡萝卜素对于HIV阳性的免疫缺陷患者有无作用目前没有定论。^[47,48] 

维生素C

维生素C刺激免疫系统，使干扰素水平^[49]和某些免疫细胞的活性增加。^[50,51]关于维生素C对老年人免疫功能的改善方面，两个不同的研究得出相反的结论率，^[52,53]另外的两个研究则没能在维生素C是否能防治肝炎的问题上达成一致。^[54,55]尽管如此，一项对20个双盲试验的回顾总结得出以下结论：尽管每天数克维生素C仅有预防感冒的小作用，但是在感冒刚开始时服用，确实能够大大缩短感冒的病程。^[56]以重体力劳动人群为研究对象的对照研究表明，每天补充维生素C 600-1,000毫克，感冒发生率平均降低50%。^[57]因此，维生素C对免疫系统的总的作用尚不清楚，其作用依情况不同而不同。

维生素A

维生素A在免疫系统功能中起重要作用，它帮助粘膜（包括肺内的粘膜）抵抗微生物的侵袭。^[58]尽管如此，多数研究显示尽管在维生素A缺乏比较常见的发展中国家，^[59]补充维生素A能帮助人们预防或治疗感染，在维生素摄取量充足的国家，补充维生素A几乎没有有效作用，甚至有轻度的副作用。^{[60,61,62,63,64,65,66]}不仅如此，只在患特定的感染性疾病时补充维生素A是有益处的。一项对多个实验的分析发现，对发展中国家的儿童，维生素A降低麻疹和腹泻的死亡率，但是不降低肺炎的死亡率。^[67]一项在坦桑尼亚患肺炎的儿童中补充维生素A的双盲研究证实维生素A在此种情况下无效。^[68]总的来说，发达国家的父母们不应该给孩子补充维生素A，除非有证据表明孩子可能缺乏维生素A，比如存在导致吸收不良的情况（例如腹部疾患）。尽管如此，美国儿科学会（the American Academy of Pediatrics）推荐所有患麻疹的儿童在具有下列情况之一时短期大剂量补充维生素A：住院，营养不良，以及其他由医生判定的特殊情况。^[69]

维生素A、C、E——复合抗氧化剂

对一组住院的老年人进行的研究表明，与安慰剂相比较，由维生素A、C、E组成的复合抗氧化剂能大大增加免疫细胞数量和活性。^[70]另一项研究发现，每天摄入1,000毫克维生素C和200国际单位维生素E，4个月后免疫功能有增强。^[71]对免疫功能有刺激作用的复合抗氧化剂到底能在多大程度上降低感染的几率目前仍不清楚。

谷氨酸

谷氨酸对于免疫系统功能是十分重要的。一些对照研究表明，对于重症患者，富含谷氨酸的流质饮食比其他饮食更有帮助。^[72,73]耐力性比赛的运动员经过繁重练习后，易患上呼吸道感染疾病，研究发现，繁重练习后，运动员血液中谷氨酸的浓度有所下降。^[74]尽管锻炼后补充谷氨酸对免疫功能的效果仍不确定，^[75,76]一项双盲试验发现，给运动员补充谷氨酸（练习完毕即给予补充2.5克，2小时后再给一次）能大大减少感染。^[77]

益生菌素

公共卫生学研究^[78,79]，以及一些对照实验^[80]表明：补充益生菌素（通过益生菌类如乳酸杆菌），或补充刺激它们在胃肠道内生长的生长因子，能够帮助保护躯体遭受肠道内有害微生物导致的局部或全身感染。益生素的有效剂量根据外来应激的张力以及不同器官内的浓度不同而不同。补充益生菌类能够有效降低儿童的感染性腹泻已经被多个实验证明，其中一部分是双盲试验。^[81,82]

胸腺提取物

胸腺与免疫系统的多种功能相关。一些研究表明，胸腺提取物Thymomodulin^®能增强免疫，一些双盲试验发现，有复发性上呼吸道感染的儿童或成人补充了Thymomodulin，感染的反复发作减少。^{[83,84,85,86,87]}双盲试验还证明，在锻炼诱导的免疫抑制患者，Thymomodulin能增强免疫，其他初步实验还证明，Thymomodulin能增强糖尿病患者和老年人的免疫功能。^{[88,89,90,91]}

锌

有报道表明，补充锌也能增强免疫功能。^[92,93]双盲试验说明，锌的这种作用对老年人尤其重要。^[94,95]一些医生推荐发生反复感染的患者补充锌，剂量为成人每天25毫克，儿童减量（根据体重）。但是，过量补充锌（如每天300毫克）被证明对免疫功能有损害。^[96]

对照实验表明锌糖能有减轻普通感冒的症状、缩短其病程，但是这种作用究竟是免疫功能增加还是锌对病毒的直接作用引起的，目前尚不清楚。^[97]

番茄红素

大剂量番茄红素能增加老年人NK细胞的活性。一项对照试验发现，15毫克番茄红素显著增加NK细胞的浓度，但是对其他免疫功能无效。^[98]

维生素B12

维生素B12缺乏与免疫功能下降有关。一项对照研究发现，维生素B12缺乏性贫血的患者体内，与免疫功能相关的白细胞水平明显下降。^[99]通过注射维生素B12的方法恢复其在体内的含量能够增加这些免疫细胞的水平，提示维生素B12对于免疫功能的重要性。

β葡聚糖

β葡聚糖是一种纤维素样多糖，衍生于面包酵母细胞壁、燕麦和大麦纤维，以及许多有药用价值的蕈类，如灰树花。大量体外研究和动物实验证明，β葡聚糖能够激活白细胞。^{[100,101,102,103,104]}实际上，自20世纪60年代以来有成百上千的关于β葡聚糖的论文。^[105]研究显示，尤其β-1,3-葡聚糖能够非常有效地激活白细胞中的巨噬细胞和中性粒细胞。β葡聚糖激活的巨噬细胞和中性粒细胞能够辨别、杀死肿瘤细胞，清除氧化损伤导致的细胞残骸，加快受损组织修复，进一步激活免疫系统的其他组分。^[106,107]尽管体外研究和动物实验令人振奋，但β葡聚糖作为口服药增强人免疫的有效性仍然存在许多问题。人们是否可以从β葡聚糖获益，以及要产生效果需要多大剂量的β葡聚糖，仍然需要通过对照试验来说明。

脱氢表雄酮（DHEA）

激素DHEA（脱氢表雄酮）也对免疫有影响。一项对照试验发现，给予一组低DHEA水平的老年人大剂量DHEA（每天50毫克）20周，免疫系统功能被显著激活。^[108]双盲试验表明，给予绝经后妇女DHEA仅三周，免疫系统功能就有增强。^[109]

Ω-3脂肪酸

食用鱼类或其他含有Ω-3脂肪酸食品的作用已经在上文中讨论过。关于补充鱼油，除了对住院患者有效外，大多数试验报道过量Ω-3脂肪酸摄入降低免疫功能。^{[110,111,112,113]}一些研究表明，抗氧化剂能纠正这个问题。^[114]

精氨酸、Ω-3脂肪酸、核苷

大多数^{[115,116,117,118,119]}——但并非所有^[120,121]——双盲试验表明，含有精氨酸、Ω-3脂肪酸以及核苷（比如核糖核酸RNA）的流质饮食对于维持重症患者和术后患者的免疫功能、减少感染发生比其他的流食更有效。这些试验中，典型的摄入量为3.3克Ω-3脂肪酸，12.5克精氨酸，1.2克RNA。没有试验研究给予患有较轻疾病的患者补充这些物质的作用。

乳清蛋白

一项双盲研究表明，对一组HIV感染患者每天给予45毫克乳清蛋白能增加血液中谷光甘肽的水平。^[122]体外试验^[123,124]和动物实验^[125]表明，乳清蛋白对免疫功能的某些部分有促进作用。

有无副作用及药物之间相互作用呢？

参见各种补充剂的副作用以及药物间相互作用。

可能有益的草药

紫锥菊

总体上，人体研究发现口服紫锥菊能刺激多种免疫细胞的功能，尤其是NK细胞。^[126]从目前各项研究获得的证据来看，紫锥菊能通过刺激免疫（而非直接杀死感冒病毒）加快普通感冒的恢复。^[127]没有证据支持用紫锥菊预防普通感冒，提示其免疫刺激活性在健康人群中很轻微。其他口服紫锥菊的研究没有发现它能够刺激中性粒细胞的活性。^[128]许多医生建议用3-5毫升紫锥菊酊剂每天三次来增强免疫功能。紫锥菊胶囊也很容易买到。

穿心莲

一项双盲研究表明，穿心莲能有效减轻普通感冒的严重程度。^[129]另一项初步研究表明它可以在健康人群中预防感冒。^[130]这些作用被认为是其活性组分穿心莲碱的免疫增强作用。^[131]

人参

亚洲人参作为传统中草药用于预防和治疗免疫系统相关疾病已经有很长久的历史了。一项双盲试验表明，健康人服用100毫克标准人参提取物每天两次能够增强免疫功能。^[132]

刺五加（西伯利亚人参）

刺五加（西伯利亚人参）也有用于支持免疫系统的历史。俄罗斯的研究说明了其传统应用。^[133]一项双盲试验表明，健康人服用刺五加酊剂10毫升每天三次能够使对免疫功能很重要的一些T细胞增加。这项试验没有研究在低免疫功能的人身上是否有这些作用。这项实验中使用的刺五加的剂量很大，但是没有发现副作用。

醉茄

醉茄被认为是对免疫系统产生一般刺激^[134]，被称为滋补品或适应原^[135]——一种多功能、非特异对抗应激效果以及普遍提高健康水平的中草药。

紫云英、灰树花、食用蘑菇

紫云英、灰树花及其他食用蘑菇中的复合多糖似乎有“免疫调节剂”的作用，因此也被用于研究其在艾滋病和癌症中的作用。目前，仅有的人体紫云英研究显示，它能够防止接受化疗和放疗患者的白细胞数量下降，还能够提高健康人群体内抗体的水平。^[136]灰树花仅在动物体内研究过，用来增强免疫功能。^[137]这些蕈类中发现的主要的免疫激活多糖，β-D-葡聚糖，通过口服吸收良好^[138]，目前正用于HIV感染者支持治疗的研究。将来的研究结果能够增进我们对于这些蕈类及其组分功效的认识。

猫爪

猫爪中发现的称为小檗碱物质已被证明能够刺激免疫系统。^[139]但是这种作用是否足以预防或治疗疾病目前仍不清楚。

冬虫夏草

动物实验和人体试验表明冬虫夏草能增强免疫^[140,141]，但仍需进一步研究免疫系统功能降低的各种情况下其功效。常用剂量是胶囊3到4.5毫克每天两次，或茶水浸泡10到15分钟后饮用。

绿茶

动物实验表明，绿茶能刺激免疫细胞增值，还有抗菌能力。^{[142,143,144]} 需要更多研究来评价绿茶预防感染和其他免疫相关疾病的功效。

何首乌

初步研究表明，何首乌有增强免疫和抗菌活性。^[145]要了解这些作用的重要性仍需要进一步研究。

女贞素（石竹酸）

女贞中的主要活性成分是女贞素（石竹酸）。关于女贞的研究多数在中国进行，发现女贞素能够刺激免疫系统。^[146]女贞在中医药中常与紫云英混合。尽管在免疫功能抑制和癌症患者中长期使用女贞作为免疫支持，但是究竟用多长时间为最佳仍需更多研究说明。

巴戟天

动物实验和体外试验表明，巴戟天有一些提高免疫的活性。尤其是其多糖成分被发现能增加免疫促进物质的释放，进而激活白细胞破坏肿瘤细胞。^[147]常规推荐剂量4盎司巴戟天汁早餐前30分钟服用（空腹时效果最佳）。巴戟天的效用仍需人体试验来证明。

有无副作用及药物之间相互作用呢？

参见各种草药的副作用及相互作用。

可能有用的整体疗法

免疫系统在应激时被抑制。慢性精神和情感压力可以使免疫功能下降，但是这是否足以增加感染或癌症发生的危险仍不清楚。^[148,149]但是，通过缓解压力的各种方法，如进行一些放松练习、生物反馈和其他途径，免疫功能可以增加^[150,151]，尽管并非所有研究都显示这些方法有明显效果。^[152]

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