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维生素 A

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发表于 2019-1-3 00:47:36 | 显示全部楼层 |阅读模式
Introduction
Vitamin A is the name of a group of fat-soluble retinoids, including retinol, retinal, and retinyl esters [1-3]. Vitamin A is involved in immune function, vision, reproduction, and cellular communication [1,4,5]. Vitamin A is critical for vision as an essential component of rhodopsin, a protein that absorbs light in the retinal receptors, and because it supports the normal differentiation and functioning of the conjunctival membranes and cornea [2-4]. Vitamin A also supports cell growth and differentiation, playing a critical role in the normal formation and maintenance of the heart, lungs, kidneys, and other organs [2].
前言
维生素A是一组脂溶性类维生素A的名称,包括视黄醇、视黄醛和视黄酯。维生素A参与免疫功能,视力,生殖和细胞通讯。维生素A作为视紫红质的必需成分是至关重要的,视紫红质是一种吸收视网膜受体中光线的蛋白质,因为它支持结膜膜和角膜的正常分化和功能。维生素A还支持细胞的生长和分化,在心、肺、肾和其他器官的正常形成和维持中起关键作用。
Two forms of vitamin A are available in the human diet: preformed vitamin A (retinol and its esterified form, retinyl ester) and provitamin A carotenoids [1-5]. Preformed vitamin A is found in foods from animal sources, including dairy products, fish, and meat (especially liver). By far the most important provitamin A carotenoid is beta-carotene; other provitamin A carotenoids are alpha-carotene and beta-cryptoxanthin. The body converts these plant pigments into vitamin A. Both provitamin A and preformed vitamin A must be metabolized intracellularly to retinal and retinoic acid, the active forms of vitamin A, to support the vitamin’s important biological functions [2,3]. Other carotenoids found in food, such as lycopene, lutein, and zeaxanthin, are not converted into vitamin A.
人类饮食中有两种形式的维生素A:维生素A前体(视黄醇及其酯化形式,视黄酯)和前维生素A类胡萝卜素。前体维生素A存在于动物来源的食物中,包括乳制品、鱼类和肉类(尤其是肝脏)。到目前为止,最重要的维生素原A类胡萝卜素是β-胡萝卜素;其他维生素原A类胡萝卜素是α-胡萝卜素和β-隐黄质。身体将这些植物色素转化为维生素A。
The various forms of vitamin A are solubilized into micelles in the intestinal lumen and absorbed by duodenal mucosal cells [5]. Both retinyl esters and provitamin A carotenoids are converted to retinol, which is oxidized to retinal and then to retinoic acid [2]. Most of the body’s vitamin A is stored in the liver in the form of retinyl esters.
前维生素A和预先形成的维生素A必须在细胞内代谢为视黄醛和视黄酸(维生素A的活性形式),以支持维生素的重要生物学功能。在食物中发现的其他类胡萝卜素,如番茄红素、叶黄素和玉米黄质,不会转化为维生素a。
Retinol and carotenoid levels are typically measured in plasma, and plasma retinol levels are useful for assessing vitamin A inadequacy. However, their value for assessing marginal vitamin A status is limited because they do not decline until vitamin A levels in the liver are almost depleted [3]. Liver vitamin A reserves can be measured indirectly through the relative dose-response test, in which plasma retinol levels are measured before and after the administration of a small amount of vitamin A [5]. A plasma retinol level increase of at least 20% indicates an inadequate vitamin A level [3,5,6]. For clinical practice purposes, plasma retinol levels alone are sufficient for documenting significant deficiency.
各种形式的维生素A在肠腔内溶解成胶束并被十二指肠粘膜细胞吸收5。视黄酯和前维生素A类胡萝卜素都转化为视黄醇,视黄醇被氧化成视黄醛,然后被氧化成视黄酸。体内大部分维生素A以视黄酯的形式储存在肝脏中。通常在血浆中测定视黄醇和类胡萝卜素水平,血浆视黄醇水平可用于评估维生素A不足。然而,它们用于评估边缘维生素A状态的价值是有限的,因为它们在肝脏中的维生素A水平几乎耗尽之前不会下降。肝脏维生素A储备可通过相对剂量反应试验间接测量,其中血浆视黄醇水平在服用少量维生素A前后测定。血浆视黄醇水平升高至少20%表明维生素A水平不足。出于临床实践的目的,单独的血浆视黄醇水平足以记录明显的缺陷。

A plasma retinol concentration lower than 0.70 micromoles/L (or 20 micrograms [mcg]/dL) reflects vitamin A inadequacy in a population, and concentrations of 0.70–1.05 micromoles/L could be marginal in some people [5]. In some studies, high plasma or serum concentrations of some provitamin A carotenoids have been associated with a lower risk of various health outcomes, but these studies have not definitively demonstrated that this relationship is causal.
血浆视黄醇浓度低于0.70微摩尔/L(或20微克 [mcg]/dL)反映了人群中维生素A的不足,在某些人群中浓度为0.70 -1.05微摩尔/L可能是微不足道的。在一些研究中,一些前维生素A类胡萝卜素的高血浆或血清浓度与各种健康结果的风险较低有关,但这些研究并未明确证明这种关系是因果关系。
Recommended Intakes
Intake recommendations for vitamin A and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the Institute of Medicine of the National Academies (formerly National Academy of Sciences) [5]. DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. These values, which vary by age and gender, include:
推荐摄入量
美国国家科学院(原美国国家科学院)医学研究所食品与营养委员会(FNB)制定的膳食参考摄入量(DRIs)中提供了维生素A和其他营养素的摄入建议。 DRI是用于规划和评估健康人营养素摄入量的一组参考值的总称。这些数值因年龄和性别而异,包括:  
Recommended Dietary Allowance (RDA): Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals; often used to plan nutritionally adequate diets for individuals.
推荐膳食补充量(RDA):每日平均摄入水平足以满足几乎所有(97% -98%)健康个体的营养需求;常用于为个体计划营养充足的饮食。
Adequate Intake (AI): Intake at this level is assumed to ensure nutritional adequacy; established when evidence is insufficient to develop an RDA.
充足的摄入量(AI):假定这一水平的摄入量确保营养充足;当证据不足以开发RDA时建立
Estimated Average Requirement (EAR): Average daily level of intake estimated to meet the requirements of 50% of healthy individuals; usually used to assess the nutrient intakes of groups of people and to plan nutritionally adequate diets for them; can also be used to assess the nutrient intakes of individuals.
估计平均需要量(EAR):估计每日平均摄入量,以满足50%的健康要求;通常用于评估人群的营养摄入量,并为其计划营养充足的饮食;也可用于评估个体的营养摄入量。
Tolerable Upper Intake Level (UL): Maximum daily intake unlikely to cause adverse health effects.

可耐受的高摄入水平(UL):每日最大摄入量不可能对健康造成不良影响。
RDAs for vitamin A are given as mcg of retinol activity equivalents (RAE) to account for the different bioactivities of retinol and provitamin A carotenoids (see Table 1). Because the body converts all dietary sources of vitamin A into retinol, 1 mcg of physiologically available retinol is equivalent to the following amounts from dietary sources: 1 mcg of retinol, 12 mcg of beta-carotene, and 24 mcg of alpha-carotene or beta-cryptoxanthin. From dietary supplements, the body converts 2 mcg of beta-carotene to 1 mcg of retinol.
Currently, vitamin A is listed on food and supplement labels in international units (IUs) even though nutrition scientists rarely use this measure. Conversion rates between mcg RAE and IU are as follows [7]:
维生素A的RDA以mcg视黄醇活性当量(RAE)给出,以说明视黄醇和前维生素A类胡萝卜素的不同生物活性(见表1)。由于人体将维生素A的所有膳食来源转化为视黄醇,1微克生理上可用的视黄醇相当于膳食来源的下列量:1微克视黄醇、12微克β-胡萝卜素和24微克α-胡萝卜素或β-隐黄质。从膳食补充剂中,身体将2微克β-胡萝卜素转化为1微克视黄醇。
1 IU retinol = 0.3 mcg RAE
1 IU视黄醇=0.3 MCG RAE
1 IU beta-carotene from dietary supplements = 0.15 mcg RAE
1 IUβ-膳食补充剂中的胡萝卜素= 0.15 mcg RAE
1 IU beta-carotene from food = 0.05 mcg RAE
1 IUβ-食物中的胡萝卜素=0.05 mcg RAE
1 IU alpha-carotene or beta-cryptoxanthin = 0.025 mcg RAE
1 IUα-胡萝卜素或β-隐黄质= 0.025 mcg RAE
However, for the manufacture and addition of preformed vitamin A and provitamin A carotenoids to dietary supplements and foods, as well as for labeling the vitamin A content of these products, the U.S. Food and Drug Administration (FDA) mandates that older conversion factors published by the FNB in 1968 be used: 1 IU = 0.3 mcg as retinol = 0.6 mcg as beta-carotene [8]. Under FDA’s new labeling regulations for foods and dietary supplements that take effect by July 26, 2018 (for companies with annual sales of $10 million or more) or July 26, 2019 (for smaller companies), vitamin A will be listed only in mcg and not IUs [9].
然而,为了在膳食补充剂和食品中制造和添加预先形成的维生素A和前维生素A类胡萝卜素,以及标记这些产品的维生素A含量,美国食品和药物管理局(FDA)要求使用1968年FNB公布的较旧的转换因子:1 IU =0.3 mcg视黄醇=0.6 mcgβ-胡萝卜素。根据FDA对2018年7月26日前生效的食品和膳食补充剂的新标签规定(对于年销售额在1000万美元或以上的公司)或2019年7月26日(对于规模较小的公司),维生素A将仅以mcg而非IU 上市。
An RAE cannot be directly converted into an IU without knowing the source(s) of vitamin A. For example, the RDA of 900 mcg RAE for adolescent and adult men is equivalent to 3,000 IU if the food or supplement source is preformed vitamin A (retinol). However, this RDA is also equivalent to 6,000 IU of beta-carotene from supplements, 18,000 IU of beta-carotene from food, or 36,000 IU of alpha-carotene or beta-cryptoxanthin from food. So a mixed diet containing 900 mcg RAE provides between 3,000 and 36,000 IU of vitamin A, depending on the foods consumed.
在不知道维生素A来源的情况下,RAE不能直接转化为IU。例如,如果食物或补充剂来源是预先形成的维生素A(视黄醇),青少年和成年男性900微克RAE的RDA相当于3,000国际单位。不过,这种RDA也相当于来自补充剂的6000国际单位的β-胡萝卜素,来自食物的18,000国际单位的β-胡萝卜素,或来自食物的36,000国际单位的α-胡萝卜素或β-隐黄质。因此,含有900微克RAE的混合饮食可提供3,000至36,000国际单位的维生素a,这取决于所消耗的食物。

* Adequate Intake (AI), equivalent to the mean intake of vitamin A in healthy, breastfed infants.
足量摄入(AI),相当于健康、母乳喂养婴儿维生素A的平均摄入量
Concentrations of preformed vitamin A are highest in liver and fish oils [2]. Other sources of preformed vitamin A are milk and eggs, which also include some provitamin A [2]. Most dietary provitamin A comes from leafy green vegetables, orange and yellow vegetables, tomato products, fruits, and some vegetable oils [2]. The top food sources of vitamin A in the U.S. diet include dairy products, liver, fish, and fortified cereals; the top sources of provitamin A include carrots, broccoli, cantaloupe, and squash [4,5].
预制维生素A的其他来源是牛奶和鸡蛋,其中也包括一些维生素原A。大多数膳食维生素原A来自绿叶蔬菜、橙黄色蔬菜、番茄制品、水果和一些植物油。 美国维生素A的顶级食物来源,饮食包括乳制品、肝脏、鱼类和强化谷物;维生素原A的最高来源包括胡萝卜、西兰花、哈密瓜和南瓜。
Table 2 suggests many dietary sources of vitamin A. The foods from animal sources in Table 2 contain primarily preformed vitamin A, the plant-based foods have provitamin A, and the foods with a mixture of ingredients from animals and plants contain both preformed vitamin A and provitamin A.
建议维生素A的许多饮食来源。表2中动物来源的食物主要含有预先形成的维生素A,植物性食物含有维生素原A,动植物成分混合物的食物含有预先形成的维生素A和维生素原A。



*DV = Daily Value. DVs were developed by the FDA to help consumers compare the nutrient contents of products within the context of a total diet. The DV for vitamin A is 5,000 IU for adults and children age 4 and older. Foods providing 20% or more of the DV are considered to be high sources of a nutrient. The U.S. Department of Agriculture’s (USDA’s) Nutrient Database Web site [10] lists the nutrient content of many foods and provides a comprehensive list of foods containing vitamin A in IUs arranged by nutrient content and by food name, and foods containing beta-carotene in mcg arranged by nutrient content and by food name.
DV=每日价值。DVs由FDA开发,旨在帮助消费者在总膳食的背景下比较产品的营养成分。成人和4岁及以上儿童的维生素A的DV为5 000 IU。提供20%或更多DV的食物被认为是营养素的高来源。美国农业部(USDA S)营养数据库网站列出了许多食物的营养成分,并提供了按营养成分和食物名称排列的含有维生素a的食物的综合列表,以及按营养成分和食物名称排列的含有β-胡萝卜素的食物。
Dietary supplements
Vitamin A is available in multivitamins and as a stand-alone supplement, often in the form of retinyl acetate or retinyl palmitate [2]. A portion of the vitamin A in some supplements is in the form of beta-carotene and the remainder is preformed vitamin A; others contain only preformed vitamin A or only beta-carotene. Supplement labels usually indicate the percentage of each form of the vitamin. The amounts of vitamin A in stand-alone supplements range widely [2]. Multivitamin supplements typically contain 2,500–10,000 IU vitamin A, often in the form of both retinol and beta-carotene.
膳食补充剂
维生素A有多种维生素和独立的补充剂,通常以醋酸视黄酯或棕榈酸视黄酯2的形式。一些补充剂中的一部分维生素A是β-胡萝卜素的形式,其余部分是预先形成的维生素A;另一些只含有预先形成的维生素A或仅含有β-胡萝卜素。补充标签通常标明每种形式的维生素的百分比。独立补充剂中维生素A的含量范围很广。多种维生素补充剂通常含有2,500 -10,000 IU维生素A,通常以视黄醇和β-胡萝卜素的形式存在。
About 28%–37% of the general population uses supplements containing vitamin A [11]. Adults aged 71 years or older and children younger than 9 are more likely than members of other age groups to take supplements containing vitamin A.
一般人群中约有28%-37%的人使用含有维生素A 的补充剂。71岁以上的成年人和9岁以下的儿童比其他年龄组的成员更可能服用含有维生素A的补充剂。
Vitamin A Intakes and Status
According to an analysis of data from the 2007–2008 National Health and Nutrition Examination Survey (NHANES), the average daily dietary vitamin A intake in Americans aged 2 years and older is 607 mcg RAE [12]. Adult men have slightly higher intakes (649 mcg RAE) than adult women (580 mcg RAE). Although these intakes are lower than the RDAs for individual men and women, these intake levels are considered to be adequate for population groups.
Data from NHANES III, conducted in 1988–1994, found that approximately 26% of the vitamin A in RAEs consumed by men and 34% of that consumed by women in the United States comes from provitamin A carotenoids, with the remainder coming from preformed vitamin A, mostly in the form of retinyl esters [5].
维生素A的摄入量和状态
根据对2007年-2008年全国健康和营养调查(NHANES)数据的分析,2岁及以上美国人平均每日膳食维生素A摄入量为607微克RAE 。成年男性的摄入量(649微克RAE)略高于成年女性(580微克RAE)。虽然这些摄入量低于个别男性和女性的RDA,但这些摄入量被认为对人群是足够的,来自1988年-1994年进行的NHANES III的数据发现,男性摄入的RAE中约26种维生素A和美国女性摄入的34种维生素A来自前维生素A类胡萝卜素,其余来自预先形成的维生素A,主要以视黄酯5的形式存在。
The adequacy of vitamin A intake decreases with age in children [4]. Furthermore, girls and African-American children have a higher risk of consuming less than two-thirds of the vitamin A RDA than other children [4].
儿童维生素A摄入的充足程度随年龄增长而降低。此外,与其他儿童相比,女孩和非裔美国儿童摄入维生素a RDA少于三分之二的风险更高。
Vitamin A Deficiency
Frank vitamin A deficiency is rare in the United States. However, vitamin A deficiency is common in many developing countries, often because residents have limited access to foods containing preformed vitamin A from animal-based food sources and they do not commonly consume available foods containing beta-carotene due to poverty [2]. According to the World Health Organization, 190 million preschool-aged children and 19.1 million pregnant women around the world have a serum retinol concentration below 0.70 micromoles/L [13]. In these countries, low vitamin A intake is most strongly associated with health consequences during periods of high nutritional demand, such as during infancy, childhood, pregnancy, and lactation.
维生素A缺乏症在许多发展中国家很常见,这往往是因为居民从动物为基础的食物来源获得含有预先形成的维生素A的食物的机会有限,而且由于贫穷,他们通常不会食用含有β-胡萝卜素的食物维生素A缺乏在美国很少见,据世界卫生组织报道,全世界有1.9亿学龄前儿童和1910万孕妇的血清视黄醇浓度低于0.70微摩尔/L .在这些国家,低维生素A摄入量与高营养需求期间的健康后果最为密切相关,如婴儿期、儿童期、妊娠期和哺乳期。
In developing countries, vitamin A deficiency typically begins during infancy, when infants do not receive adequate supplies of colostrum or breast milk [13]. Chronic diarrhea also leads to excessive loss of vitamin A in young children, and vitamin A deficiency increases the risk of diarrhea [5,14]. The most common symptom of vitamin A deficiency in young children and pregnant women is xerophthalmia. One of the early signs of xerophthalmia is night blindness, or the inability to see in low light or darkness [2,15]. Vitamin A deficiency is one of the top causes of preventable blindness in children [13]. People with vitamin A deficiency (and, often, xerophthalmia with its characteristic Bitot’s spots) tend to have low iron status, which can lead to anemia [3,13]. Vitamin A deficiency also increases the severity and mortality risk of infections (particularly diarrhea and measles) even before the onset of xerophthalmia [5,13,15].
在发展中国家,维生素A缺乏症通常始于婴儿期,当时婴儿得不到充足的初乳或母乳供应。慢性腹泻还会导致幼儿维生素A丢失过多,维生素A缺乏会增加腹泻的风险。 幼儿和孕妇维生素A缺乏最常见的症状是干眼症。干眼症的早期征兆之一是夜盲症,或无法在低光照或黑暗中看到.维生素A缺乏是儿童可预防失明的主要原因之一。
Groups at Risk of Vitamin A Inadequacy
The following groups are among those most likely to have inadequate intakes of vitamin A.
有维生素A缺乏风险的群体
以下群体是最有可能维生素A摄入不足的群体。
Premature Infants In developed countries, clinical vitamin A deficiency is rare in infants and occurs only in those with malabsorption disorders [16]. However, preterm infants do not have adequate liver stores of vitamin A at birth and their plasma concentrations of retinol often remain low throughout the first year of life [16,17]. Preterm infants with vitamin A deficiency have an increased risk of eye, chronic lung, and gastrointestinal diseases [16].
在发达国家的早产儿中,临床上维生素A缺乏在婴儿中少见,仅发生在有吸收障碍的患儿。然而,早产儿在出生时并没有足够的维生素A肝脏储存,其血浆视黄醇浓度在整个生命的第一年常常保持低水平.维生素A缺乏的早产儿患眼、慢性肺和胃肠道疾病的风险增加。
Infants and Young Children in Developing Countries
In developed countries, the amounts of vitamin A in breast milk are sufficient to meet infants’ needs for the first 6 months of life. But in women with vitamin A deficiency, breast milk volume and vitamin A content are suboptimal and not sufficient to maintain adequate vitamin A stores in infants who are exclusively breastfed [18]. The prevalence of vitamin A deficiency in developing countries begins to increase in young children just after they stop breastfeeding [3]. The most common and readily recognized symptom of vitamin A deficiency in infants and children is xerophthalmia.

发展中国家的婴幼儿
在发达国家,母乳中维生素A的量足以满足婴儿生命最初6个月的需要。但在维生素A缺乏的妇女中,母乳量和维生素A含量并不理想,不足以维持纯母乳喂养婴儿充足的维生素A储存。 刚停止母乳喂养的幼儿,维生素A缺乏症在发展中国家的患病率开始增加。婴儿和儿童维生素A缺乏最常见和最易被认识的症状是干眼症。
Pregnant and Lactating Women in Developing Countries 发展中国家的孕妇和哺乳期妇女
Pregnant women need extra vitamin A for fetal growth and tissue maintenance and for supporting their own metabolism [19]. The World Health Organization estimates that 9.8 million pregnant women around the world have xerophthalmia as a result of vitamin A deficiency [13]. Other effects of vitamin A deficiency in pregnant and lactating women include increased maternal and infant morbidity and mortality, increased anemia risk, and slower infant growth and development.
孕妇需要额外的维生素A用于胎儿生长和组织维持以及支持自身代谢。世界卫生组织估计全世界有980万孕妇因维生素a缺乏而出现干眼症. 孕妇和哺乳期妇女维生素A缺乏的其他影响包括母婴发病率和死亡率增加,贫血风险增加,婴儿生长发育减慢。
People with Cystic Fibrosis
Most people with cystic fibrosis have pancreatic insufficiency, increasing their risk of vitamin A deficiency due to difficulty absorbing fat [20,21]. Several cross-sectional studies found that 15%–40% of patients with cystic fibrosis have vitamin A deficiency [22]. However, improved pancreatic replacement treatments, better nutrition, and caloric supplements have helped most patients with cystic fibrosis become vitamin A sufficient [21]. Several studies have shown that oral supplementation can correct low serum beta-carotene levels in people with cystic fibrosis, but no controlled studies have examined the effects of vitamin A supplementation on clinical outcomes in patients with cystic fibrosis [21-23].

囊性纤维化患者
大多数囊性纤维化患者存在胰腺功能不全,由于难以吸收脂肪而增加其维生素A缺乏的风险。几项横断面研究发现,15%-40%的囊性纤维化患者存在维生素A缺乏。然而,改善胰腺替代治疗、更好的营养和热量补充已经帮助大多数囊性纤维化患者成为足够的维生素A。几项研究表明,口服补充剂可以纠正囊性纤维化患者的低血清β-胡萝卜素水平,但没有对照研究检测补充维生素A对囊性纤维化患者临床结局的影响。

Vitamin A and Health
This section focuses on three diseases and disorders in which vitamin A might play a role: cancer, age-related macular degeneration (AMD), and measles.

维生素A与健康
本节重点介绍维生素A可能发挥作用的三种疾病和病症:癌症、年龄相关性黄斑变性(AMD)和麻疹。
Cancer  
Because of the role vitamin A plays in regulating cell growth and differentiation, several studies have examined the association between vitamin A and various types of cancer. However, the relationship between serum vitamin A levels or vitamin A supplementation and cancer risk is unclear.
肿瘤
由于维生素A在调节细胞生长和分化中的作用,一些研究已经检查了维生素A与各种类型癌症之间的关联。然而,血清维生素A水平或补充维生素A与癌症风险之间的关系尚不清楚

Several prospective and retrospective observational studies in current and former smokers, as well as in people who have never smoked, found that higher intakes of carotenoids, fruits and vegetables, or both are associated with a lower risk of lung cancer [1,24]. However, clinical trials have not shown that supplemental beta-carotene and/or vitamin A helps prevent lung cancer. In the Carotene and Retinol Efficacy Trial (CARET), 18,314 current and former smokers (including some males who had been occupationally exposed to asbestos) took daily supplements containing 30 mg beta-carotene and 25,000 IU retinyl palmitate for 4 years, on average [25]. In the Alpha-Tocopherol, Beta-Carotene (ATBC) Cancer Prevention Study, 29,133 male smokers took 50 mg/day alpha-tocopherol, 20 mg/day beta-carotene, 50 mg/day alpha-tocopherol and 20 mg/day beta-carotene, or placebo for 5–8 years [26]. In the beta-carotene component of the Physicians’ Health Study, 22,071 male physicians took 325 mg aspirin plus 50 mg beta-carotene, 50 mg beta-carotene plus aspirin placebo, 325 mg aspirin plus beta-carotene placebo, or both placebos every other day for 12 years [27]. In all three of these studies, taking very high doses of beta-carotene, with or without 25,000 IU retinyl palmitate or 325 mg aspirin, did not prevent lung cancer. In fact, both the CARET and ATBC studies showed a significant increase in lung cancer risk among study participants taking beta-carotene supplements or beta-carotene and retinyl palmitate supplements. The Physicians’ Health Study did not find an increased lung cancer risk in participants taking beta-carotene supplements, possibly because only 11% of physicians in the study were current or former smokers.
对目前和过去吸烟者以及从未吸烟的人群进行的几项前瞻性和回顾性观察性研究发现,较高的类胡萝卜素、水果和蔬菜或两者的摄入量与较低的肺癌风险相关。但临床试验并未显示补充β-胡萝卜素和/或维生素A有助于预防肺癌。在胡萝卜素和视黄醇药效试验(CARET)中,18,314名现吸烟者和前吸烟者(包括一些曾职业接触过石棉的男性)平均每天服用含有30mgβ-胡萝卜素和25,000iu棕榈酸视黄酯的补充剂4年。在α-生育酚,β-胡萝卜素(ATBC)癌症预防研究中,29133名男性吸烟者服用50毫克每日α-生育酚,20毫克每日β-胡萝卜素,50毫克每日α-生育酚和20毫克每日β-胡萝卜素,或安慰剂5 -8年。在医师健康研究的β-胡萝卜素成分中,22,071名男性医师每隔一天服用325mg阿司匹林加50mgβ-胡萝卜素,50mgβ-胡萝卜素加阿司匹林安慰剂,325mg阿司匹林加β-胡萝卜素安慰剂,或两种安慰剂,共12年,在所有这三项研究中,服用非常高剂量的β-胡萝卜素,加或不加25,000 IU棕榈酸视黄酯或325 mg阿司匹林,都不能预防肺癌。事实上,CARET和ATBC研究都显示服用β-胡萝卜素补充剂或β-胡萝卜素和棕榈酸视黄酯补充剂的研究参与者中肺癌风险显着增加。Physicians Health研究没有发现服用β-胡萝卜素补充剂的参与者肺癌风险增加,可能是因为研究中只有11名医生是现在或过去的吸烟者。
The evidence on the relationship between beta-carotene and prostate cancer is mixed. CARET study participants who took daily supplements of beta-carotene and retinyl palmitate had a 35% lower risk of nonaggressive prostate cancer than men not taking the supplements [28]. However, the ATBC study found that baseline serum beta-carotene and retinol levels and supplemental beta-carotene had no effect on survival [29]. Moreover, men in the highest quintile of baseline serum retinol levels were 20% more likely to develop prostate cancer than men in the lowest quintile [30].
关于β-胡萝卜素与前列腺癌关系的证据不一。每日服用β-胡萝卜素和棕榈酸视黄酯补充剂的CARET研究参与者比未服用补充剂的男性患前列腺癌的风险低35%,然而,ATBC研究发现基线血清β-胡萝卜素和视黄醇水平以及补充β-胡萝卜素对生存没有影响。此外,基线血清视黄醇水平最高五分位数的男性患前列腺癌的可能性比最低五分位数的男性高20%
The ATBC and CARET study results suggest that large supplemental doses of beta-carotene with or without retinyl palmitate have detrimental effects in current or former smokers and workers exposed to asbestos. The relevance of these results to people who have never smoked or to the effects of beta-carotene or retinol from food or multivitamins (which typically have modest amounts of beta-carotene) is not known. More research is needed to determine the effects of vitamin A on prostate, lung, and other types of cancer.
ATBC和CARET研究结果表明,大剂量补充β-胡萝卜素(含或不含棕榈酸视黄酯)对目前或过去的吸烟者和接触石棉的工人有不利影响。这些结果与从未吸烟的人或来自食物或多种维生素(通常含有适量的β-胡萝卜素)的β-胡萝卜素或视黄醇的影响的相关性尚不清楚。 需要更多的研究来确定维生素A对前列腺癌,肺癌和其他类型癌症的影响  
Age-Related Macular Degeneration
Age-related macular degeneration (AMD) is a major cause of significant vision loss in older people. AMD’s etiology is usually unknown, but the cumulative effect of oxidative stress is postulated to play a role. If so, supplements containing carotenoids with antioxidant functions, such as beta-carotene, lutein, and zeaxanthin, might be useful for preventing or treating this condition. Lutein and zeaxanthin, in particular, accumulate in the retina, the tissue in the eye that is damaged by AMD.
年龄相关性黄斑变性
年龄相关性黄斑变性(AMD)是导致老年人视力明显下降的主要原因。其病因尚不清楚,但猜测是氧化应激的累积效应起作用。如果是这样,含有具有抗氧化功能的类胡萝卜素的补充剂,如β-胡萝卜素、叶黄素和玉米黄质,可能对预防或治疗这种病症有用。 特别是叶黄素和玉米黄质在视网膜中积累,视网膜是眼睛中被AMD损伤的组织。
The Age-Related Eye Disease Study (AREDS), a large randomized clinical trial, found that participants at high risk of developing advanced AMD (i.e., those with intermediate AMD or those with advanced AMD in one eye) reduced their risk of developing advanced AMD by 25% by taking a daily supplement containing beta-carotene (15 mg), vitamin E (400 IU dl-alpha-tocopheryl acetate), vitamin C (500 mg), zinc (80 mg), and copper (2 mg) for 5 years compared to participants taking a placebo [31].
年龄相关性眼病研究(AREDS)是一项大型随机临床试验,研究发现,与服用安慰剂的参与者相比,服用含有β-胡萝卜素(15 mg),维生素e(400 IU dl-α-生育酚乙酸酯),维生素C(500 mg),锌(80 mg)和铜(2 mg)的每日补充剂5年,可降25%的晚期AMD的发生风险。
A follow-up AREDS2 study confirmed the value of this supplement in reducing the progression of AMD over a median follow-up period of 5 years but found that adding lutein (10 mg) and zeaxanthin (2 mg) or omega-3 fatty acids to the formulation did not confer any additional benefits [32]. Importantly, the study revealed that beta-carotene was not a required ingredient; the original AREDS formulation without beta-carotene provided the same protective effect against developing advanced AMD. In a more detailed analysis of results, supplementation with lutein and zeaxanthin reduced the risk of advanced AMD by 26% in participants with the lowest dietary intakes of these two carotenoids who took a supplement containing them compared to those who did not take a supplement with these carotenoids [32]. The risk of advanced AMD was also 18% lower in participants who took the modified AREDS supplement containing lutein and zeaxanthin but not beta-carotene than in participants who took the formulation with beta-carotene but not lutein or zeaxanthin.
一项随访的AREDS2研究证实了该补充剂在中位随访期5年内减少AMD进展的价值,但发现在制剂中添加叶黄素(10 mg)和玉米黄质(2 mg)或ω-3脂肪酸并没有赋予任何额外的益处,重要的是,研究揭示了β-胡萝卜素不是必需的成分;不含β-胡萝卜素的原始AREDS制剂对发展为晚期AMD提供了相同的保护作用。在更详细的结果分析中,补充叶黄素和玉米黄质可使饮食摄入最低的这两种类胡萝卜素的参与者患晚期AMD的风险降低26%,与那些没有补充这些类胡萝卜素的人相比,这两种类胡萝卜素的膳食摄入量最低,服用含叶黄素和玉米黄质但不含β-胡萝卜素的改良AREDS补充剂的参与者比服用含β-胡萝卜素但不含叶黄素或玉米黄质的制剂的参与者的晚期AMD风险也低18%。
Individuals who have or are developing AMD should talk to their healthcare provider about taking one of the supplement formulations used in AREDS.
已经或正在开发AMD的个人应该与他们的医疗保健提供者谈论服用ARED中使用的一种补充剂配方。

Measles
Measles is a major cause of morbidity and mortality in children in developing countries. About half of all measles deaths happen in Africa, but the disease is not limited to low-income countries. Vitamin A deficiency is a known risk factor for severe measles. The World Health Organization recommends high oral doses (200,000 IU) of vitamin A for two days for children over age 1 with measles who live in areas with a high prevalence of vitamin A deficiency [33].

麻疹
麻疹是发展中国家儿童发病和死亡的主要原因。大约一半的麻疹死亡发生在非洲,但这种疾病并不局限于低收入国家。维生素A缺乏是严重麻疹的已知危险因素。世界卫生组织建议1岁以上麻疹患儿在维生素A缺乏高发地区口服高剂量(20万IU)维生素A 2天

A Cochrane review of eight randomized controlled trials of treatment with vitamin A for children with measles found that 200,000 IU of vitamin A on each of two consecutive days reduced mortality from measles in children younger than 2 and mortality due to pneumonia in children [33]. Vitamin A also reduced the incidence of croup but not pneumonia or diarrhea, although the mean duration of fever, pneumonia, and diarrhea was shorter in children who received vitamin A supplements. A meta-analysis of six high-quality randomized controlled trials of measles treatment also found that two doses of 100,000 IU in infants and 200,000 IU in older children significantly reduced measles mortality [34]. The vitamin A doses used in these studies are much higher than the UL. The effectiveness of vitamin A supplementation to treat measles in countries, such as the United States, where vitamin A intakes are usually adequate is uncertain.
对8项针对麻疹患儿使用维生素A治疗的随机对照试验的回顾发现,连续两天每天服用20万IU维生素A可降低2岁以下儿童麻疹死亡率和儿童肺炎死亡率,虽然接受维生素A补充剂的儿童的发热、肺炎和腹泻的平均持续时间较短,但维生素A也可降低哮吼的发生率,但不降低肺炎或腹泻的发生率。对6项高质量的麻疹治疗随机对照试验的荟萃分析也发现,婴儿10万IU和大龄儿童20万IU两种剂量可显著降低麻疹死亡率,这些研究中使用的维生素A剂量远高于UL。在维生素A摄入量通常充足的国家,如美国,补充维生素A治疗麻疹的有效性尚不确定。
The body needs vitamin A to maintain the corneas and other epithelial surfaces, so the lower serum concentrations of vitamin A associated with measles, especially in people with protein-calorie malnutrition, can lead to blindness. None of the studies evaluated in a Cochrane review evaluated blindness as a primary outcome [35]. However, a careful clinical investigation of 130 African children with measles revealed that half of all corneal ulcers in these children, and nearly all bilateral blindness, occurred in those with vitamin A deficiency [36].
人体需要维生素A来维持角膜和其他上皮表面,因此与麻疹相关的维生素A血清浓度较低,特别是在蛋白质卡路里营养不良的人群中,会导致失明。Cochrane评价中评估的研究均未将盲目性评估为主要结果,然而,对130名非洲儿童麻疹患者进行了仔细的临床调查,发现这些儿童角膜溃疡的一半,以及几乎所有的双侧失明,都发生在维生素a缺乏者
Health Risks from Excessive Vitamin A
Because vitamin A is fat soluble, the body stores excess amounts, primarily in the liver, and these levels can accumulate. Although excess preformed vitamin A can have significant toxicity (known as hypervitaminosis A), large amounts of beta-carotene and other provitamin A carotenoids are not associated with major adverse effects [37]. The manifestations of hypervitaminosis A depend on the size and rapidity of the excess intake. The symptoms of hypervitaminosis A following sudden, massive intakes of vitamin A, as with Arctic explorers who ate polar bear liver, are acute [38]. Chronic intakes of excess vitamin A lead to increased intracranial pressure (pseudotumor cerebri), dizziness, nausea, headaches, skin irritation, pain in joints and bones, coma, and even death [2,4,5]. Although hypervitaminosis A can be due to excessive dietary intakes, the condition is usually a result of consuming too much preformed vitamin A from supplements or therapeutic retinoids [3,5]. When people consume too much vitamin A, their tissue levels take a long time to fall after they discontinue their intake, and the resulting liver damage is not always reversible.

维生素A过量带来的健康风险
因为维生素A是脂溶性的,身体储存过量,主要在肝脏,这些水平可以积累。尽管过量的预先形成的维生素A可能具有明显的毒性(称为维生素A过多症),但大量的β-胡萝卜素和其他维生素原A类胡萝卜素与主要不良反应无关,维生素A过多症的表现取决于过量摄入的大小和速度。维生素A过多症的症状突然大量摄入维生素A后,与北极探险者吃北极熊肝一样,是急性表现,慢性摄入过量的维生素A会导致颅内压增高(假性脑瘤),头晕,恶心,头痛,皮肤刺激,关节和骨骼疼痛,昏迷,甚至死亡,虽然维生素A过多症可能是由于饮食摄入过多所致,但这种情况通常是由于从补充剂或治疗性类维生素A中摄入过多的预先形成的维生素A所致。当人们摄入过多的维生素A后,其组织水平在停止摄入后需要较长时间才能下降,由此导致的肝脏损伤并不总是可逆的。
Observational studies have suggested an association between high intakes of preformed vitamin A (more than 1,500 mcg daily—only slightly higher than the RDA), reduced bone mineral density, and increased fracture risk [1,4,39]. However, the results of studies on this risk have been mixed, so the safe retinol intake level for this association is unknown.
观察性研究表明,预先形成的维生素A的高摄入量(每日超过1500微克,仅略高于RDA)、骨密度降低和骨折风险增加之间存在关联。然而,关于这一风险的研究结果却参差不齐,因此该协会的安全视黄醇摄入水平是未知的。
Total intakes of preformed vitamin A that exceed the UL and some synthetic retinoids used as topical therapies (such as isotretinoin and etretinate) can cause congenital birth defects [2-4]. These birth defects can include malformations of the eye, skull, lungs, and heart [4]. Women who might be pregnant should not take high doses of vitamin A supplements [2].
超过UL的预先形成的维生素A和用作局部疗法的一些合成类维生素A(如异维A酸和维A酸)的总摄入量可导致先天性出生缺陷。这些出生缺陷可包括眼、颅骨、肺和心脏的畸形,可能怀孕的妇女不宜服用高剂量的维生素A补充剂
Unlike preformed vitamin A, beta-carotene is not known to be teratogenic or lead to reproductive toxicity [1]. And even large supplemental doses (20–30 mg/day) of beta-carotene or diets with high levels of carotenoid-rich food for long periods are not associated with toxicity. The most significant effect of long-term, excess beta-carotene is carotenodermia, a harmless condition in which the skin becomes yellow-orange [1,24]. This condition can be reversed by discontinuing beta-carotene ingestion.
与预先形成的维生素A不同,β-胡萝卜素未知致畸还是导致生殖毒性,而且即使是大剂量的补充剂量(每天20 -30毫克)的β-胡萝卜素或长期食用富含类胡萝卜素含量高的食物也与毒性无关。长期、过量的β-胡萝卜素最显著的影响是胡萝卜素皮症,一种皮肤变成黄橙色的无害状况,这种情况可以通过停止摄取β-胡萝卜素来逆转。
Supplementation with beta-carotene, with or without retinyl palmitate, for 5–8 years has been associated with an increased risk of lung cancer and cardiovascular disease in current and former male and female smokers and in male current and former smokers occupationally exposed to asbestos [26,40]. In the ATBC study, beta-carotene supplements (20 mg daily) were also associated with increased mortality, mainly due to lung cancer and ischemic heart disease [26]. The CARET study ended early, after the investigators found that daily beta-carotene (30 mg) and retinyl palmitate (25,000 IU) supplements increased the risk of lung cancer and cardiovascular disease mortality [40].
补充β-胡萝卜素(含或不含棕榈酸视黄酯)5 -8年与目前和过去的男性和女性吸烟者以及职业接触石棉的男性当前和过去吸烟者的肺癌和心血管疾病风险增加有关,在ATBC研究中,β-胡萝卜素补充剂(每日20毫克)也与死亡率增加有关,主要是由于肺癌和缺血性心脏病。CARET研究提前结束,研究者发现每日补充β-胡萝卜素(30 mg)和棕榈酸视黄酯(25,000 IU)会增加肺癌和心血管疾病死亡率的风险
The FNB has established ULs for preformed vitamin A that apply to both food and supplement intakes [5]. The FNB based these ULs on the amounts associated with an increased risk of liver abnormalities in men and women, teratogenic effects, and a range of toxic effects in infants and children. The FNB also considered levels of preformed vitamin A associated with decreased bone mineral density, but did not use these data as the basis for its ULs because the evidence was conflicting. The FNB has not established ULs for beta-carotene and other provitamin A carotenoids [24]. The FNB advises against beta-carotene supplements for the general population, except as a provitamin A source to prevent vitamin A deficiency.

FNB已经建立了适用于食物和补充剂摄入的预先形成的维生素A的ULs,FNB基于这些UL与男性和女性肝脏异常风险增加、致畸作用、以及对婴儿和儿童的一系列毒性作用。FNB还考虑了与骨密度降低相关的预先形成的维生素A水平,但没有将这些数据作为其ULs的基础,因为证据是相互矛盾的。FNB尚未建立β-胡萝卜素和其他维生素原A类胡萝卜素的UL,FNB建议不要给普通人群补充β-胡萝卜素,除非作为预防维生素a缺乏的维生素原a来源。

* These ULs, expressed in mcg and in IUs (where 1 mcg = 3.33 IU), only apply to products from animal sources and supplements whose vitamin A comes entirely from retinol or ester forms, such as retinyl palmitate. However, many dietary supplements (such as multivitamins) do not provide all of their vitamin A as retinol or its ester forms. For example, the vitamin A in some supplements consists partly or entirely of beta-carotene or other provitamin A carotenoids. In such cases, the percentage of retinol or retinyl ester in the supplement should be used to determine whether an individual’s vitamin A intake exceeds the UL. For example, a supplement labeled as containing 10,000 IU of vitamin A with 60% from beta-carotene (and therefore 40% from retinol or retinyl ester) provides 4,000 IU of preformed vitamin A. That amount is above the UL for children from birth to 13 years but below the UL for adolescents and adults.
这些UL以微克和国际单位(其中1微克3.33国际单位)表示,仅适用于维生素A完全来自视黄醇或酯形式的动物源和补充剂的产品,如棕榈酸视黄酯。然而,许多膳食补充剂(如多种维生素)不能提供维生素a的全部视黄醇或其酯形式。例如,一些补充剂中的维生素A部分或全部由β-胡萝卜素或其他维生素原A类胡萝卜素组成。在这种情况下,应使用补充剂中视黄醇或视黄酯的百分比来确定个体的维生素A摄入量是否超过UL。例如,标记为含有10,000国际单位维生素a和60%来自β-胡萝卜素(因此40%来自视黄醇或视黄酯)的补充剂可提供4,000国际单位的预制维生素a。从出生到13岁的儿童,这一数额高于UL,而青少年和成人则低于UL。
Interactions with Medications
Vitamin A can interact with certain medications, and some medications can have an adverse effect on vitamin A levels. A few examples are provided below. Individuals taking these and other medications on a regular basis should discuss their vitamin A status with their healthcare providers.
与药物的相互作用
维生素A可与某些药物相互作用,有些药物可对维生素A水平产生不利影响。下面提供几个例子。定期服用这些和其他药物的个人应与他们的医疗保健提供者讨论他们的维生素a状况
Orlistat
Orlistat (Alli®, Xenical®), a weight-loss treatment, can decrease the absorption of vitamin A, other fat-soluble vitamins, and beta-carotene, causing low plasma levels in some patients [41]. The manufacturers of Alli and Xenical recommend encouraging patients on orlistat to take a multivitamin supplement containing vitamin A and beta-carotene, as well as other fat-soluble vitamins [42,43].
Retinoids
奥利司他
奥利司他(Allifi,Xenicalfi)是一种减肥治疗药物,可降低维生素a、其他脂溶性维生素和β-胡萝卜素的吸收,导致部分患者血浆水平低,Alli和Xenical的制造商建议鼓励奥利司他患者服用含有维生素a和β-胡萝卜素以及其他脂溶性维生素的多种维生素补充剂
Several synthetic retinoids derived from vitamin A are used orally as prescription medicines. Examples include the psoriasis treatment acitretin (Soriatane®) and bexarotene (Targretin®), used to treat the skin effects of T-cell lymphoma. Retinoids can increase the risk of hypervitaminosis A when taken in combination with vitamin A supplements [41].
几种由维生素A衍生的合成类维生素A口服用作处方药。 例如银屑病治疗药物阿维a(Soriatanefi)和贝沙罗汀(Targretinfi),用于治疗T细胞淋巴瘤的皮肤效应。维甲酸与维生素A补充剂合用可增加维生素A过多症的风险  
Vitamin A and Healthful Diets
The federal government’s 2015-2020 Dietary Guidelines for Americans notes that “Nutritional needs should be met primarily from foods. … Foods in nutrient-dense forms contain essential vitamins and minerals and also dietary fiber and other naturally occurring substances that may have positive health effects. In some cases, fortified foods and dietary supplements may be useful in providing one or more nutrients that otherwise may be consumed in less-than-recommended amounts.”

维生素A和健康饮食
联邦政府2015-2020年美国人膳食指南指出应主要从食物中满足营养需要。营养密集形式的食物含有必需的维生素和矿物质,还有膳食纤维和其他可能对健康产生积极影响的天然物质。在某些情况下,强化食品和膳食补充剂可能有助于提供一种或多种营养素,否则这些营养素的消耗量可能低于推荐量。
For more information about building a healthy diet, refer to the Dietary Guidelines for Americans and the U.S. Department of Agriculture’s MyPlate.
The Dietary Guidelines for Americans describes a healthy eating pattern as one that:
Includes a variety of vegetables, fruits, whole grains, fat-free or low-fat milk and milk products, and oils.
Many fruits, vegetables, and dairy products are good sources of vitamin A. Some ready-to-eat breakfast cereals are fortified with vitamin A.
Includes a variety of protein foods, including seafood, lean meats and poultry, eggs, legumes (beans and peas), nuts, seeds, and soy products.
Beef liver contains high amounts of vitamin A. Other sources of the nutrient include some fish, beans, and nuts.
Limits saturated and trans fats, added sugars, and sodium.
Stays within your daily calorie needs.
美国人的膳食指南描述了一种健康的饮食模式:包括各种蔬菜、水果、全谷物、无脂或低脂牛奶及奶制品和油。许多水果、蔬菜和奶制品都是维生素A的良好来源。   一些现成的早餐麦片中添加了维生素A。 包括多种蛋白质食品,包括海鲜、瘦肉和家禽、鸡蛋、豆类(豆类和豌豆)、坚果、种子和豆制品。 牛肝中含有大量的维生素A。其他的营养来源包括一些鱼、豆类和坚果。限制饱和和反式脂肪、添加的糖和钠。保持在你每天所需的卡路里之内。
References
Johnson EJ, Russell RM. Beta-Carotene. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:115-20.
Ross CA. Vitamin A. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:778-91.
Ross A. Vitamin A and Carotenoids. In: Shils M, Shike M, Ross A, Caballero B, Cousins R, eds. Modern Nutrition in Health and Disease. 10th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2006:351-75.
Solomons NW. Vitamin A. In: Bowman B, Russell R, eds. Present Knowledge in Nutrition. 9th ed. Washington, DC: International Life Sciences Institute; 2006:157-83.
Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press; 2001.
Tanumihardjo SA. Vitamin A: biomarkers of nutrition for development. Am J Clin Nutr 2011;94:658S-65S. [PubMed abstract]
Otten JJ, Hellwig JP, Meyers LD, eds. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, DC: The National Academies Press; 2006.
Food and Nutrition Board. Recommended Dietary Allowances, 7th ed. Washington, DC: National Academy of Sciences; 1968.
Food and Drug Administration. Food labeling: Revision of the Nutrition and Supplement Facts labels. Federal Register 2016;81:33741-999.
U.S. Department of Agriculture, Agricultural Research Service. USDA National Nutrient Database for Standard Reference, Release 24. Nutrient Data Laboratory Home Page, 2011.
Bailey RL, Gahche JJ, Lentino CV, Dwyer JT, Engel JS, Thomas PR, et al. Dietary supplement use in the United States, 2003-2006. J Nutr 2011;141:261-6. [PubMed abstract]
U.S. Department of Agriculture, Agricultural Research Service. What We Eat in America, 2007-2008.
World Health Organization. Global Prevalence of Vitamin A Deficiency in Populations at Risk 1995–2005: WHO Global Database on Vitamin A Deficiency. Geneva: World Health Organization; 2009.
Mayo-Wilson E, Imdad A, Herzer K, Yakoob MY, Bhutta ZA. Vitamin A supplements for preventing mortality, illness, and blindness in children aged under 5: systematic review and meta-analysis. BMJ 2011;343:d5094. [PubMed abstract]
Sommer A. Vitamin A deficiency and clinical disease: An historical overview. J Nutr 2008;138:1835-9. [PubMed abstract]
Mactier H, Weaver LT. Vitamin A and preterm infants: what we know, what we don’t know, and what we need to know. Arch Dis Child Fetal Neonatal Ed 2005;90:F103-8. [PubMed abstract]
Darlow BA, Graham PJ. Vitamin A supplementation to prevent mortality and short and long-term morbidity in very low birthweight infants. Cochrane Database Syst Rev 2007:CD000501. [PubMed abstract]
Oliveira-Menegozzo JM, Bergamaschi DP, Middleton P, East CE. Vitamin A supplementation for postpartum women. Cochrane Database Syst Rev 2010:CD005944. [PubMed abstract]
van den Broek N, Dou L, Othman M, Neilson JP, Gates S, Gulmezoglu AM. Vitamin A supplementation during pregnancy for maternal and newborn outcomes. Cochrane Database Syst Rev 2010:CD008666. [PubMed abstract]
Graham-Maar RC, Schall JI, Stettler N, Zemel BS, Stallings VA. Elevated vitamin A intake and serum retinol in preadolescent children with cystic fibrosis. Am J Clin Nutr 2006;84:174-82. [PubMed abstract]
O’Neil C, Shevill E, Chang AB. Vitamin A supplementation for cystic fibrosis. Cochrane Database Syst Rev 2010:CD006751.pub2. [PubMed abstract]
Borowitz D, Baker RD, Stallings V. Consensus report on nutrition for pediatric patients with cystic fibrosis. J Pediatr Gastroenterol Nutr 2002;35:246-59.
Michel SH, Maqbool A, Hanna MD, Mascarenhas M. Nutrition management of pediatric patients who have cystic fibrosis. Pediatr Clin North Am 2009;56:1123-41. [PubMed abstract]
Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Press; 2000.
Omenn GS, Goodman GE, Thornquist MD, Balmes J, Cullen MR, Glass A, et al. Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med 1996;334:1150-5. [PubMed abstract]
The Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study Group. The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. N Engl J Med 1994;330:1029-35. [PubMed abstract]
Hennekens CH, Buring JE, Manson JE, Stampfer M, Rosner B, Cook NR, et al. Lack of effect of long-term supplementation with beta carotene on the incidence of malignant neoplasms and cardiovascular disease. The New England journal of medicine 1996;334:1145-9. [PubMed abstract]
Neuhouser ML, Barnett MJ, Kristal AR, Ambrosone CB, King IB, Thornquist M, et al. Dietary supplement use and prostate cancer risk in the Carotene and Retinol Efficacy Trial. Cancer Epidemiol Biomarkers Prev 2009;18:2202-6. [PubMed abstract]
Watters JL, Gail MH, Weinstein SJ, Virtamo J, Albanes D. Associations between alpha-tocopherol, beta-carotene, and retinol and prostate cancer survival. Cancer Res 2009;69:3833-41. [PubMed abstract]
Mondul AM, Watters JL, Mannisto S, Weinstein SJ, Snyder K, Virtamo J, et al. Serum retinol and risk of prostate cancer. Am J Epidemiol 2011;173:813-21. [PubMed abstract]
Age-Related Eye Disease Study Research Group. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8. Arch Ophthalmol 2001;119:1417-36. [PubMed abstract]
The Age-Related Eye Disease Study 2 (AREDS2) Research Group. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: the Age-Related Eye Disease Study 2 (AREDS2) randomized clinical trial. JAMA 2013;309:2005-15. [PubMed abstract]
Yang HM, Mao M, Wan C. Vitamin A for treating measles in children. Cochrane Database Syst Rev 2011;2005.
Sudfeld CR, Navar AM, Halsey NA. Effectiveness of measles vaccination and vitamin A treatment. Int J Epidemiol 2010;39 Suppl 1:i48-55. [PubMed abstract]
Bello S, Meremikwu MM, Ejemot-Nwadiaro RI, Oduwole O. Routine vitamin A supplementation for the prevention of blindness due to measles infection in children. Cochrane Database Syst Rev 2011:CD007719. [PubMed abstract]
Foster A, Sommer A. Corneal ulceration, measles, and childhood blindness in Tanzania. Br J Ophthalmol 1987;71:331-43. [PubMed abstract]
Grune T, Lietz G, Palou A, Ross AC, Stahl W, Tang G, et al. Beta-carotene is an important vitamin A source for humans. The Journal of Nutrition 2010;140:2268S-85S. [PubMed abstract]
Rodahl K, Moore T. The vitamin A content and toxicity of bear and seal liver. Biochem J 1943;37:166-8. [PubMed abstract]
Ribaya-Mercado JD, Blumberg JB. Vitamin A: is it a risk factor for osteoporosis and bone fracture? Nutr Rev 2007;65:425-38. [PubMed abstract]
Goodman GE, Thornquist MD, Balmes J, Cullen MR, Meyskens FL, Omenn GS, et al. The beta-carotene and retinol efficacy trial: incidence of lung cancer and cardiovascular disease mortality during 6-year follow-up after stopping β-carotene and retinol supplements. J Natl Cancer Inst 2004;96:1743-50. [PubMed abstract]
Natural Medicines Comprehensive Database. Vitamin A. 2011.
Genentech USA, Inc. Xenical Package Insert. 2010.
GlaxoSmithKline. Alli: Potential for Misuse and Drug Interactions. 2011.
Disclaimer
This fact sheet by the Office of Dietary Supplements (ODS) provides information that should not take the place of medical advice. We encourage you to talk to your healthcare providers (doctor, registered dietitian, pharmacist, etc.) about your interest in, questions about, or use of dietary supplements and what may be best for your overall health. Any mention in this publication of a specific product or service, or recommendation from an organization or professional society, does not represent an endorsement by ODS of that product, service, or expert advice.


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