空谷幽兰最后solo:有关维生素C,的资料,

维生素C又叫抗坏血酸，是一种水溶性维生素。在所有维生素中，维生素C是最不稳定的。在贮藏，加工和烹调时，容易被破坏。它还易被氧化和分解。

一、维生素C主要生理功能

1、 促进骨胶原的生物合成。利于组织创伤口的更快愈合；

2、 促进氨基酸中酪氨酸和色氨酸的代谢，延长肌体寿命。

3、 改善铁、钙和叶酸的利用。

4、 改善脂肪和类脂特别是胆固醇的代谢，预防心血管病。

5、 促进牙齿和骨骼的生长，防止牙床出血。；

6、 增强肌体对外界环境的抗应激能力和免疫力。

二、维生素C缺乏和疾病

维生素C缺乏时，其症状表现为：

1． 牙龈肿胀出血，牙床溃烂、牙齿松动。

2． 骨骼畸形、易骨折。

3． 伤口难愈合等。进一步则引起坏血症、贫血。

4． 大出血和心脏衰竭，严重时有猝死的危险。

5． 肌肉纤维衰退，包括心肌衰退。

维生素C是无毒的营养素，但每天摄入量超过八克会有害，症状包括：恶心，腹部痉挛，腹泻，铁的过量吸收，红血球破坏，骨骼矿物质代谢增强，防碍抗凝剂的治疗，血浆胆固醇升高，并可能对大剂量维生素C形成依赖。

三、维生素C主要食物来源有哪些？

猕猴桃、樱桃、柑橘类水果、番石榴、青椒或红辣椒、西红柿、芥菜、菠菜、草莓、卷心菜、土豆、葡萄以及番茄等.
药物作用
维生素C在体内参与多种反应，如参与氧化还原过程，在生物氧化和还原作用以及细胞呼吸中起重要作用。从组织水平看，维生素C的主要作用是与细胞间质的合成有关。包括胶原，牙和骨的基质，以及毛细血管内皮细胞间的接合物。因此，当维生素C缺乏所引起的坏血病时，伴有胶原合成缺陷，表现为创伤通难以愈合，牙齿形成障碍和毛细血管破损引起大量瘀血点，瘀血点融合形成瘀斑。

维生素C基本知识

维生素C又叫L-抗坏血酸，是一种水溶性维生素，能够治疗坏血病并且具有酸性，所以称作抗坏血酸。在柠檬汁、绿色植物及番茄中含量很高。抗坏血酸是单斜片晶或针晶，容易被氧化而生成脱氢坏血酸，脱氢坏血酸仍具有维生素C的作用。在碱性溶液中，脱氢坏血酸分子中的内酯环容易被水解成二酮古洛酸。维生素C可辅助治疗多种疾病，维生素C不仅能预防和减轻感冒症状，还能增强免疫力预防心脏病发生。

一般的描述
几乎所有的动物和植物综合有像人类和少数的其他动物这样的一些例外的他们自己的维他命 C., 包括, 猿，天竺鼠, 红色发泄的夜莺, 一个吃水果的蝙蝠和一个鳟鱼的种。 这已经引导一些科学家, 包括保罗假定的林诺斯这些种或遗失了 (或者从不有了) 能力生产他们自己的维他命 C, 而且如果他们的饮食与对在确实综合他们自己的维他命 C 的动物种被生产的数量的许多营养的比例项一起补充,较好的健康会产生。

维他命 C 首先在 1928 年被隔离，而且在 1932 年它被证明当避免坏血病的代理人。 艾伯特 Szent-Gy?rgyi 对于这一个壮举在医学被颁发 1937 诺贝尔奖。

维他命 C 是一种弱的酸, ascorbic 酸或含盐的甜 ascorbate 叫做。 它是 L-ascorbic 酸的 enantiomer D-enantiomer 没有表示生物学的活动。 两者都是反映相同化学的分子结构的图像表格, 见到光学的异构体).

物质的活跃部份是 ascorbate 离子, 能表达它本身如中立的或些微基本的一种酸或 ascorbate 的盐。 商业的维他命 C 时常是一个 ascorbic 酸的混合, 钠 ascorbate 及[或] 其他的 ascorbates 。 一些补充物部份地包含 D-enantiomer, 是无用的和无害处的。 为分子的化学特性的完全描述见到 ascorbic 酸文章。

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在身体中动作
如 hydroxylation 的一个叁加者，维他命 C 在连接着薄的纱织品中是对胶原蛋白的生产的需要。 这些纤维在身体各处是到处存在的,除了有柔性的结构之外提供公司。 一些薄的纱织品有胶原蛋白的较棒的百分比, 尤其: 剥皮, 黏液的薄膜，牙齿和 [硬]骨。
维他命 C 为神经系统或肾上腺的神经传导物质， noradrenaline 和肾上腺素的综合被需要。
维他命 C 也被需要综合 carnitine, 重要的在能源的移动方面对细胞 mitochondria。
和最好的百分比的维他命 C 的薄纱织品 - 在血浆中的超过 100 次水平 - 肾上腺，垂体，胸腺，集成 luteum 和视网膜是。
脑，脾，肺，睾丸，淋巴结，肝，甲状腺，小的肠黏膜，白血球，胰, 肾和唾液的腺通常有 10 到 50 在血浆中乘集中礼物。
维他命 C 是对于 ascorbate peroxidase 如一个基体的一个抗氧化物和行为。
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维他命 C 缺乏
没有身体的器官储存如一个主要的功能 ascorbate, 而且因此如果新鲜的补给没被消耗过消化的系统，身体很快 ascorbate 耗尽它本身, 最后带领如果维他命 C 的消费及时没被重新开始，对即是坏血病 (一种维他命缺乏症的形式) 的缺乏疾病，这造成疾病和死亡。

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敏锐的坏血病
敏锐的坏血病有:的特点

容易的打伤, 或以没有明显的因素打伤
释放牙齿
表面出血
血管的脆弱
贫穷的痊愈
妥协处理免疫
温和的贫血
对巨大的内在出血带领, 坏血病最后致命, 而且是在水手之中的一种通常的情况和在冬天期间。 敏锐的坏血病在工业化的国家中现在非常稀有。

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每日的需求和剂量家眷效果
为在人类中维持最佳的健康有在维他命 C 的最好的剂量时间表 (数量和摄取的频度) 上的科学群落里面的连续的辩论。[1]

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政府机关推荐摄取水平
没有补充的一种均衡的饮食包含充足的维他命 C 在一个平均的健康成体中避免敏锐的坏血病。 因为吸烟的人, 那些在压迫力之下, 和孕妇它些微地多拿。

对于维他命 C 摄取的忠告依下列各项已经被各种不同国家的代理商设定:

一天 40个毫克: 食物标准代理商 (英国)[2]

一天 60-95个毫克 , 饮食的叁考摄取 (DRI),推荐每日的津贴 (RDA) ，美国食物和营养董事会 2004[3] 。

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独立的剂量忠告
一些科学家已经在下列的理由上批评政府机关剂量忠告。[引证需要]

他们不考虑个别的不同 , 像是年龄，重量, 等等举例来说，较沈重的个体通常需要较多的维他命 C。
身材表现 , 数量需要避免敏锐形式的缺乏疾病, 当次临床水平的时候疾病不是甚至公认。
数量需要避免其他的疾病不是考虑过的。
最佳的健康不是考虑, 因为健康的程度对准是那哪一个边缘地比那哪一个被视为营养不良的好。
一些研究员已经计算数量对一个成人的人类需要达成如依下列各项综合哺乳动物的维他命 C 的相似血清水平:

每一天 - 林诺斯的 Pauling 的每日推荐的 6000-18000个毫克
每一天 - 汤姆斯的征税 6000-12000个毫克, 科罗拉多统合的医生集中推荐。
在疾病或怀孕 (达 300g 对于一些疾病) 期间的一天 3000个毫克或更多 - 维他命 C 基金会的推荐。 [8]
一天 400个毫克 - 林诺斯保罗学会 & 美国国家卫生局 (NIH) 推荐。
从 3000个毫克到以被罗勃特 Cathcart 描述的一个记录为基础的一天 200,000个毫克 [即是扩大维他命 C 的剂量的维他命 C 流溢 wherin 的 4] 有，直到腹泻发展, 然后选择不引起腹泻 (肠宽容阈值) 的最高的剂量. 高的剂量 (数以千计毫克) 可能造成腹泻,如果剂量立刻被减少，这是无害处的。 一些研究员[4] 要求腹泻的攻击是身体的真实维他命 C 需求躺卧的地方指示。 两者的 Cathcart[4] 和卡梅伦已经示范非常不舒服患有癌的病人或流行性感冒一点也不显示任何对于腹泻的证据直到 ascorbate 摄取到达水平高达 200 克 (? 强烈打击).
然而，给维他命 C 的生物学的 halflife 相当短, 大约 30 分钟在血浆中, 哪些 NIH 和 IM 研究员一种事实仍然没有认识。 NIH 研究员建立 , 现在的 RDA 基于 , 测试在消费之后引导了 12 小时 (24个半的生命) 。 "是钝的 ," 说机械， "NIH 给予了被等候的一份维他命 C 的剂量直到它已经被排泄 , 然后测量了血[液] 水平 ."[9]

为维他命 C(见到下面的拥护争论) 的大剂量有一次强烈的拥护运动,虽然不是所有的谣传利益被医学建立支援。 许多赞成维他命的 C 组织促进很好超过现在的饮食叁考摄取 (DRI) 的用法水平。

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治疗的申请和剂量
维他命 C 在饮食被需要避免坏血病,然而, 从当它以 1930 年代的纯粹形式变成可得了的时候，一些开业者为坏血病之外的疾病以如治疗的维他命 C 作实验了。 大多数的着名人士在 Reidsville ，北卡罗莱那州中大体上是佛烈德 R. Klenner ，一位医生练习。 他利用了口头的和静脉内的维他命 C 对待一个各类型的传染和毒药。他在 1949 年出版了一张纸 , 那描述了他如何已经见到对充分大的剂量维他命 C 的小儿麻痹症生产量。

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心脏病
维他命 C 在为心脏病, 另外二存在含氨基的酸离氨酸和 nicotinic 酸 (一种维他命 B 3 的形式) 被请准专利治疗的林诺斯 Pauling 是三种成分的主要部份。

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滤过性毒菌的疾病 , 和毒药
当作为一个低成本和保险箱方法的时候， Orthomolecular 药和科学意见的少数见到维他命 C 治疗滤过性毒菌的疾病并且处理各类型的毒药。

维他命 C 为在寒冷和感冒的治疗中是有用的有增加的名誉,由于显着生物化学家的它的推荐林诺斯保罗。 自从 Pauling 的流行书以后在数年中，有关维他命 C ，关于在健康和药的大于维他命 C 的 RDA 数量的医学主管当局的一般协议已经保持难懂。 Ascorbate 用法在研究决定于一些一天克, 然而, 已经与减少的寒冷期间和严重的症状有关, 可能地抗组织胺剂效果的结果 [10]. 最高的剂量治疗,出版了被医生提倡的特定 orthomolecular 治疗政权的临床结果。 Klenner(重复的 4 治疗,400-700+ 毫克/公斤/日子 ) 和 Cathcart(对肠宽容的口试使用[4], 向上到 ~一天 150 克 ascorbate 对于感冒),已经实验式地保持被传统医学的主管当局不演说长达数十年之久。

维他命 C 基础每 20-30 分钟推荐维他命 C 的达 8 克的开始用法 [13] 为了要在进步方面的寒冷传染的症状上表示效果。表现简直没有效果的大部份的研究 ascorbate, 像是 100个毫克对藉着维他命 C 提倡者被视为 " 小的 " 的一天 500个毫克雇用剂量。 相等地重要地, 血浆高的剂量 ascorbate 的一半生活是大约 30 分钟, 暗示大部分高的剂量研究已经方法有缺陷而且会被期望表示一种最小的利益。 分开剂量补充的临床实验,在药理学理由上预测是有效的, 只有很少地没有被在文学报告。 对于高剂量维他命 C 的本质上所有要求保持合乎科学地被驳倒。 维他命 C 的大的和时常发生剂量的临床效力是一个开着的科学疑问。

在 2002 年 meta-在有传染性疾病的治疗中进入在 ascorbic 酸的效力方面的所有的被出版的研究之内学习和毒素被引导, 在～手边汤姆斯征税, 在丹佛的科罗拉多统合的医生中心的医学指导者。他要求证据为一个各类型的滤过性毒菌的传染的它的治疗角色存在而且对于蛇的治疗咬。

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带领中毒
也有证据那一粒维他命 C 是有用的在避免铅中毒，可能地对螯状来自身体的有毒的重金属帮助方面。 [14]

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巨蟹座
在 2005 年在国家卫生局的 vitro 研究方面指出对癌细胞的一些菌株，被在药理学集中 (也就是静脉内的) 方面先取地管理的维他命 C 是有毒的。 作家注意: "这些调查结果把似有道理给癌治疗的静脉内的 ascorbic 酸, 而且有 H2 O2 可能是有益的对于传染的治疗的料想不到的含意 ." 这一个研究似乎支援林诺斯 Pauling 的宣称维他命 C 能用来对抗癌。[5]

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大瀑布
它也被建议维他命 C 可能避免大瀑布的形成。 [6]

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其他的效果
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禁止征候
给一个 25 岁男性的美国规定的食物叁考摄取可容忍的上面摄取水平 (UL) 是 2,000个毫克/日子。 维他命 C 被辨认出是为药所知的最没有有毒的物质之一。 给鼠的它的 LD50 是 11,900 毫克公斤-1[15],[16],[17].

主要的关心是人由于不寻常的或者向铁超载情况,包括 hemochromatosis不演说。 维他命 C 提高铁吸收。 如果铁的受难者超载，情况带 , 克按规定尺寸制作维他命 C 的剂量了, 他们由于可提高的铁吸收可能使更坏 , 铁超载。
不充分的葡萄糖 -6-磷酸盐的 dehydrogenase 酵素 (G6 PD) 水平 , 一种遗传基因的情况,可能使一些个体偏爱一些食物和药物的特定氧物质礼物的摄取后的 hemolytic 贫血。 这包括重复的, 那里的维他命 C. 的非常大静脉内的或者口头药量是 G6 PD 缺乏可用的一个测试 [18]. 高的剂量维他命 E 已经被计划如一个潜在的给予保护的因素。
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副作用
如果接受量超过对个体的变数的一个界限，维他命 C 引起每个人的腹泻。 Cathcart[4] 已经呼叫这限制肠宽容界限而且观察它在患有重病的人中比那些健康良好者更高。 它在严重地生病的人中排范围从在健康的个体一天 5 到 25 克到一天 300 克, 像是那些用爱滋病和癌。 虽然它可能是不便的，腹泻副作用是无害处的。 腹泻将会停止一旦剂量被减少就。
维他命 C 的大剂量可能引起酸的消化不良 (颠复的胃), 特别地当接受一个空的胃。 这个不愉快的但是无害处的副作用能被连同一餐一起藉由服用维他命避免, 或藉由弥补它的酸味藉由带抗酸剂 , 像是碳酸氢钠。
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声称的有害效果
维他命 C 的有害效果的报告容易接受全球的棒突起媒体。 同样地，这些报告容易产生 , 很多的辩论和深入对维他命 C. 的较多研究在下面被描述的一些有害效果已经被证明在较迟的研究是无理由的而其他的效果仍然正在遭受较进一步的分析。

在 1998 年四月，日记自然报告维他命 C. 的过度剂量的声称致癌和产生畸形效果效果被在测试管实验方面和在只有自由基的伤害 DNA 的 20个作记号的人中二个身上注意。 他们没有被来自活的生物的较进一步的证据支援。 [7]
在 2000 年四月，南加州研究员的大学在带高的维他命 C 剂量的人中报告脖子的动脉的一个使厚。 它稍后被这能被综合对更厚和更强壮的动脉墙壁带领的角色的维他命 C 的胶原蛋白解释的维他命 C 提倡者指出了。 (裁判员。6个帕拉 10)
在 2004 年六月, 公爵大学研究员向 osteo 报告一种增加的感受性的事-在天竺鼠的关节炎然而喂了一种富含维他命 C. 的饮食, 一项 2003项研究在 Ume? 在瑞典的大学, 发现 "维他命 C 的血浆水平, retinol 和尿的酸对被讲到风湿性关节炎疾病活动的变数反的是有相互关系的 ."
被深思的肾结石的增加危险可能是在大于常态数量 (>1 g) 中服用维他命 C 的副作用。行动的潜在机制透过维他命 C(ascorbic 酸) 的代谢对 dehydroascorbic 酸, 然后被使物质交替到醋浆草的酸[被需要的引证], 一个肾结石的已知成份。 然而，这一个议题仍然是争论的, 藉由被呈现的证据为 [8] 和反对 [9] 这边效果的可能性。 维他命 B 6 可能藉由减退草酸盐生产镇静这危险 [10]. 另外地， thiamine 可能禁止草酸盐形成。 此外, 改正任何的镁缺乏 [11] 可能藉由减退草酸盐结晶减少肾结石的危险。 增加一个流动的摄取也帮助到在肾中避免草酸盐结晶。 有证据一个人的肠植物将会影响多少维他命 C 被转换到草酸盐。 病人用 predispostion 形成草酸盐石头或者或者那些在 hemodialysis 上应该避免维他命 C 的过度使用。
[12][13][14]

" 弹回坏血病 " 是理论上,不曾观察, 可以发生的情况当维他命 C 的每日摄取从非常大的数量到相对低的数量快速地被减少的时候。提倡者建议这是发生的重捆效果的夸张因为 ascorbate-在摄取被降低, 而且用光没有在被再补足的维他命 C 之后，依赖的酵素反应继续 24-48 小时。 效果是对对短量的时间小于常态的较低的浆液维他命 C 血[液] 集中。 在这个时间的期间，透过减少的抵抗有寒冷或感冒传染的微小危险。在一些天被停工的酵素反应和血清回返里面到正常水平的某人不采取大的补充物。 这不是下流, 哪一个拿零维他命 C 消费的数个星期生产症状。 它是某事服用大的维他命 C 的人补充需要知道为了要逐渐地减少药量而不愿离开突然服用维他命 C。 (裁判员。6个帕拉 4) 这是那些动人的补充物的理论上的危险 - 举例来说如果他们严重地有害地找他们自己, 和在没有补充物的一所医院中, 每次何时他们需要正常的或者比较好水平的维他命 C 对抗疾病 (裁判员。[4] 和寻找 " 主要的问题 "). 在这次，许多医生和医院职员不更加大约知道也不管理补充物的 megadosing, 所以病人可能必须仰赖朋友或者亲戚带给他们他们的补充物。
一些作家 [15] 已经识别来自维他命 C 的高剂量的贫穷铜吸收的理论上危险,虽然一点的实验证据支援这。 然而， ceruloplasmin 水平明确地似乎被高的维他命 C 摄取降低。 在一项研究，维他命 C 的 600 毫克每日在年轻的男人中没有减少铜吸收或者全部的身体铜状态, 但是导致了与由铜缺乏所引起的那些类似的比较低度的 ceruloplasmin[16]. 在另外的, ceruloplasmin 水平重要地被减少 [17].
有能在怀孕的在 4 之下的女人数个星期中引诱一个流产的在维他命 C 的一天大约 12 克配的一些民间疗法 proponants 之中流通的故事。 [18] 这然而不是被科学研究支援的。 [19]
最近的研究进入如可能的帮忙维他命 E 和 C 的使用之内在阻止氧化的压迫力对前子间带领方面仍然没有表示任何的利益,[20] 但是确实增加被忍受一项研究的低 birthweight 的宝贝的比率。[21]
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维他命 C 的来源
维他命 C 被获得过相当多世界的种群的饮食。 最富有的天然来源是水果和蔬菜, 和那些， camu camu 水果和 billygoat 李子包含维他命的最高集中。 它也存在于肉的一些削减, 尤其肝。 维他命 C 是那最广泛地带营养副食品和从平板和纯粹的 ascorbic 酸水晶的饮料混合以多种表格是可得的在被膜中或如平原粉。

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种植来源

萝丝臀部是一个维他命 CCitrus 水果 (橘色，柠檬，柚子, 石灰) ，蕃茄和马铃薯的特别地富有来源是维他命 C. 的好通常来源包括木瓜，绿花椰菜的维他命 C 的好来源的其他的食物, brussels 使发芽, 黑色的葡萄干，草莓，花椰菜，菠菜，香瓜， kiwifruit, 蔓越橘和红色的胡椒粉。

当印度的醋栗树, 是维他命 C 的最富有已知来源之一的时候， Emblica officinalis 时常提及 (新鲜果肉或缺少汁的达 900个毫克/100g 的 720个毫克/100g.)- 它包含 30 次在柳橙被发现的数量。

在植物起源的食物的维他命 C 的数量仰赖:

植物的精确变种,
土壤情况
它成长的气候,
时间的长度自从它之后被挑选,
储藏情况,
准备的方法。 在个别项目中煮时常被说破坏维他命 C- 但是在食物准备上见到派。
下列的桌形体是大约的而且在不同的生肉厂来源中表示亲戚丰度。 数量被屈服水果或者蔬菜的每 100 miligrams 克。 (在比较中, 一茶匙纯粹的维他命 C 秤重 4,500 miligrams)。。

植物来源数量
比利山羊李子 3150
Camu Camu 2800
Wolfberry 2500
萝丝臀部 2000
Acerola 1600
Amla 720
Seabuckthorn 600
枣树 500
宝贝树 400
黑醋栗 200
红色的胡椒粉 190
荷兰芹 130
番石榴 100
Kiwifruit 90
绿花椰菜 90
大杨莓 80
Redcurrant 80
布鲁塞尔使发芽 80
Lychee 70
柿子 60
木瓜 60
植物来源数量
草莓 60
橘色 50
柠檬 40
甜瓜, 香瓜 40
花椰菜 40
柚子 30
悬钩子 30
橘子 30
过于文雅的橘色 30
强烈的感情水果 30
菠菜 30
卷心菜生的绿色 30
以石灰处理 20
芒果 20
甜瓜, honeydew 20
蕃茄 10
越橘 10
凤梨 10
Pawpaw 10
葡萄 10
种植酸的

维生素C的分子式是C6H8O6,水溶液呈酸性,高温或较长时间受热易损耗,许多新鲜水果,蔬菜,乳制品中都含有丰富的维生素C 。

General description
Almost all animals and plants synthesize their own vitamin C. There are some exceptions, such as humans and a small number of other animals, including, apes, guinea pigs, the red-vented bulbul, a fruit-eating bat and a species of trout. This has led some scientists, including Linus Pauling to hypothesize that these species either lost (or never had) the ability to produce their own Vitamin C, and that if their diets were supplemented with an amount of the nutrient proportional to the amount produced in animal species that do synthesize their own Vitamin C, better health would result.

Vitamin C was first isolated in 1928, and in 1932 it was proved to be the agent which prevents scurvy. Albert Szent-Györgyi was awarded the 1937 Nobel Prize in Medicine for this feat.

Vitamin C is a weak acid, called ascorbic acid or a salt ascorbate. It is the L-enantiomer of ascorbic acid The D-enantiomer shows no biological activity. Both are mirror image forms of the same chemical molecular structure, see optical isomers).

The active part of the substance is the ascorbate ion, which can express itself as either an acid or a salt of ascorbate that is neutral or slightly basic. Commercial vitamin C is often a mix of ascorbic acid, sodium ascorbate and/or other ascorbates. Some supplements contain in part the D-enantiomer, which is useless and harmless. See the ascorbic acid article for a full description of the molecule's chemical properties.

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Functions in the body
As a participant in hydroxylation, vitamin C is needed for the production of collagen in the connective tissue. These fibers are ubiquitous throughout the body, providing firm but flexible structure. Some tissues have a greater percentage of collagen, especially: skin, mucous membranes, teeth and bones.
Vitamin C is required for synthesis of dopamine, noradrenaline and adrenaline in the nervous system or in the adrenal glands.
Vitamin C is also needed to synthesize carnitine, important in the transfer of energy to the cell mitochondria.
The tissues with greatest percentage of vitamin C — over 100 times the level in blood plasma — are the adrenal glands, pituitary, thymus, corpus luteum, and retina.
The brain, spleen, lung, testicle, lymph nodes, liver, thyroid, small intestinal mucosa, leukocytes, pancreas, kidney and salivary glands usually have 10 to 50 times the concentration present in plasma.
Vitamin C is an antioxidant and acts as a substrate for ascorbate peroxidase.
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Vitamin C deficiency
No bodily organ stores ascorbate as a primary function, and so the body soon depletes itself of ascorbate if fresh supplies are not consumed through the digestive system, eventually leading to the deficiency disease known as scurvy (a form of avitaminosis), which results in illness and death if consumption of vitamin C is not resumed in time.

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Acute scurvy
Acute scurvy is characterized by:

easy bruising, or bruising with no apparent cause
loose teeth
superficial bleeding
fragility of blood vessels
poor healing
compromised immunity
mild anemia
Leading to massive internal hemorrhaging, scurvy is eventually fatal, and was a common condition among sailors and during winter. Acute scurvy is now very rare in industrialized countries.

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Daily requirements and dose dependant effects
There is continuing debate within the scientific community over the best dose schedule (the amount and frequency of intake) of Vitamin C for maintaining optimal health in humans.[1]

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Government agency recommended intake levels
A balanced diet without supplementation contains enough Vitamin C to prevent acute scurvy in an average healthy adult. For people who smoke, those under stress, and pregnant women it takes slightly more.

Recommendations for vitamin C intake have been set by various national agencies as follows:

40 mg per day: Food Standards Agency (UK) [2]

60–95 mg per day, Dietary Reference Intake (DRI), Recommended Daily Allowance (RDA), U.S. Food and Nutrition Board 2004 [3].

[edit]
Independent dose recommendations
Some scientists have criticised governmental agency dose recommendations on the following grounds.[citation needed]

They don't take into account individual differences such as age, weight, etc. For example, heavier individuals generally need more vitamin C.
The figures represent the amount needed to prevent the acute form of deficiency disease, while subclinical levels of the disease are not even acknowledged.
The amount needed to prevent other diseases is not considered.
Optimal health is not a consideration, as the level of health targeted is that which is marginally better than that which is considered malnourished.
Some researchers have calculated the amount needed for an adult human to achieve similar blood serum levels as Vitamin C synthesising mammals as follows:

6000-18000 mg per day – Linus Pauling's daily recommendation
6000-12000 mg per day – Thomas Levy, Colorado Integrative Medical Centre recommendation.
3000 mg per day or more during illness or pregnancy (up to 300g for some illnesses) – Vitamin C Foundation's recommendation. [8]
400 mg per day – Linus Pauling Institute & US National Institutes of Health (NIH) Recommendation.
from 3000 mg to 200,000 mg per day based on a protocol described by Robert Cathcart [4] known as a vitamin C flush wherin escalating doses of Vitamin C are given until diarrhea develops, then choosing the highest dose that does not cause diarrhea (bowel tolerance threshold). High doses (thousands of mg) may result in diarrhea, which is harmless if the dose is reduced immediately. Some researchers[4] claim the onset of diarrhea to be an indication of where the body’s true vitamin C requirement lies. Both Cathcart[4] and Cameron have demonstrated that very sick patients with cancer or influenza do not display any evidence of diarrhea at all until ascorbate intake reaches levels as high as 200 grams (½ pound).
However, the biological halflife for vitamin C is quite short, about 30 minutes in blood plasma, a fact which NIH and IM researchers have failed to recognize. NIH researchers established the current RDA based upon tests conducted 12 hours (24 half lives) after consumption. "To be blunt," says Hickey, "the NIH gave a dose of vitamin C, waited until it had been excreted, and then measured blood levels."[9]

There is a strong advocacy movement for large doses of Vitamin C (see Advocacy arguments below), although not all purported benefits are supported by the medical establishment. Many pro-Vitamin C organizations promote usage levels well beyond the current Dietary Reference Intake (DRI).

[edit]
Therapeutic applications and doses
Vitamin C is needed in the diet to prevent scurvy, however, from the time it became available in pure form in the 1930s, some practitioners experimented with vitamin C as a treatment for diseases other than scurvy. Most notable was Fred R. Klenner, a doctor in general practice in Reidsville, North Carolina. He utilized both oral and intravenous vitamin C to treat a wide range of infections and poisons. He published a paper in 1949 that described how he had seen poliomyelitis yield to vitamin C in sufficiently large doses.

[edit]
Heart disease
Vitamin C is the main of the three ingredients in Linus Pauling's patented cure for heart disease, the other two being the amino acid lysine and nicotinic acid (a form of Vitamin B3).

[edit]
Viral diseases, and poisons
Orthomolecular medicine and a minority of scientific opinion sees vitamin C as being a low cost and safe way to treat viral disease and to deal with a wide range of poisons.

Vitamin C has a growing reputation for being useful in the treatment of colds and flu, owing to its recommendation by prominent biochemist Linus Pauling. In the years since Pauling's popular books about vitamin C, general agreement by medical authorities about larger than RDA amounts of vitamin C in health and medicine has remained elusive. Ascorbate usage in studies of up to several grams per day, however, have been associated with decreased cold duration and severity of symptoms, possibly as a result of an antihistamine effect [10]. The highest dose treatments, published clinical results of specific orthomolecular therapy regimes pioneered by Drs. Klenner (repeated IV treatments, 400-700+ mg/kg/day [11][12]) and Cathcart (oral use to bowel tolerance[4], up to ~150 grams ascorbate per day for flu), have remained experimentally unaddressed by conventional medical authorities for decades.

The Vitamin C Foundation recommends an initial usage of up to 8 grams of vitamin C every 20-30 minutes [13] in order to show an effect on the symptoms of a cold infection that is in progress. Most of the studies showing little or no effect employ doses of ascorbate such as 100 mg to 500 mg per day, considered "small" by vitamin C advocates. Equally importantly, the plasma half life of high dose ascorbate is approximately 30 minutes, which implies that most high dose studies have been methodologically defective and would be expected to show a minimum benefit. Clinical studies of divided dose supplementation, predicted on pharmacological grounds to be effective, have only rarely been reported in the literature. Essentially all the claims for high dose vitamin C remain to be scientifically refuted. The clinical effectiveness of large and frequent doses of vitamin C is an open scientific question.

In 2002 a meta-study into all the published research on effectiveness of ascorbic acid in the treatment of infectious disease and toxins was conducted, by Thomas Levy, Medical Director of the Colorado Integrative Medical Centre in Denver. He claimed that evidence exists for its therapeutic role in a wide range of viral infections and for the treatment of snake bites.

[edit]
Lead poisoning
There is also evidence that Vitamin C is useful in preventing lead poisoning, possibly helping to chelate the toxic heavy metal from the body. [14]

[edit]
Cancer
In 2005 in vitro research by the National Institutes of Health indicated that Vitamin C administered in pharmacological concentrations (i.e. intravenous) was preferentially toxic to several strains of cancer cells. The authors noted: "These findings give plausibility to intravenous ascorbic acid in cancer treatment, and have unexpected implications for treatment of infections where H2O2 may be beneficial." This research appeared to support Linus Pauling's claims that Vitamin C can be used to fight cancer.[5]

[edit]
Cataracts
It has been also suggested that Vitamin C might prevent the formation of cataracts. [6]

[edit]
Other effects
[edit]
Contraindications
The U.S. Dietary Reference Intake Tolerable Upper Intake Level (UL) for a 25-year old male is 2,000 mg/day. Vitamin C is recognized to be one of the least toxic substances known to medicine. Its LD50 for rats is 11,900 mg kg-1 [15], [16], [17].

A primary concern is people with unusual or unaddressed iron overload conditions, including hemochromatosis. Vitamin C enhances iron absorption. If sufferers of iron overload conditions take gram sized doses of Vitamin C, they may worsen the iron overload due to enhanced iron absorption.
Inadequate Glucose-6-phosphate dehydrogenase enzyme (G6PD) levels, a genetic condition, may predispose some individuals to hemolytic anemia after intake of specific oxidizing substances present in some food and drugs. This includes repeated, very large intravenous or oral dosages of vitamin C. There is a test available for G6PD deficiency [18]. High dose Vitamin E has been proposed as a potential protective factor.
[edit]
Side-effects
Vitamin C causes diarrhea in everyone if taken in quantities beyond a limit which is variable to the individual. Cathcart[4] has called this limit the Bowel Tolerance Limit and observed that it is higher in people with serious illness than those in good health. It ranges from 5 to 25 grams per day in healthy individuals to 300 grams per day in the seriously ill persons, such as those with AIDS and cancer. The diarrhea side-effect is harmless though it can be inconvenient. The diarrhea will cease as soon as the dose is reduced.
Large doses of vitamin C may cause acid indigestion (stomach upset), particularly when taken on an empty stomach. This unpleasant but harmless side-effect can be avoided by taking the vitamin along with meals, or by offsetting its acidity by taking an antacid such as baking soda.
[edit]
Alleged harmful effects
Reports of harmful effects of vitamin C tend to receive great prominence in the world's media. As such, these reports tend to generate much debate and more research into Vitamin C. Some of the harmful effects described below have been proven to be unfounded in later studies, while other effects are still undergoing further analysis.

In April 1998 the journal Nature reported alleged carcinogenic and teratogenic effects of excessive doses of vitamin C. The effects were noted in test tube experiments and on only two of the 20 markers of free radical damage to DNA. They have not been supported by further evidence from living organisms. [7]
In April 2000, University of Southern California researchers reported a thickening of the arteries of the neck in persons taking high vitamin C doses. It was later pointed out by vitamin C advocates that this can be explained by vitamin C's collagen synthesising role leading to thicker and stronger artery walls. (ref.6 para 10)
In June 2004, Duke University researchers reported an increased susceptibility to osteo-arthritis in guinea pigs fed a diet high in vitamin C. However, a 2003 study at Umeå University in Sweden, found that "the plasma levels of vitamin C, retinol and uric acid were inversely correlated to variables related to rheumatoid arthritis disease activity."
A speculated increased risk of kidney stones may be a side effect of taking Vitamin C in larger than normal amounts (>1g). The potential mechanism of action is through the metabolism of Vitamin C (ascorbic acid) to dehydroascorbic acid, which is then metabolized to oxalic acid[citation needed], a known constituent of kidney stones. However, this issue is still controversial, with evidence being presented for [8] and against [9] the possibility of this side effect. Vitamin B6 may mitigate this risk by decreasing oxalate production [10]. Additionally, thiamine may inhibit oxalate formation. Furthermore, correcting any magnesium deficiency [11] may decrease the risk of kidney stones by decreasing oxalate crystallization. Increasing one's fluid intake also helps to preventing oxalate crystallization in the kidney. There is evidence that a person's intestinal flora will influence how much vitamin C is converted to oxalate. Patients with a predispostion to form oxalate stones or or those on hemodialysis should avoid excess use of vitamin C.
[12][13][14]

"Rebound scurvy" is a theoretical, never observed, condition that could occur when daily intake of Vitamin C is rapidly reduced from a very large amount to a relatively low amount. Advocates suggest this is an exaggeration of the rebound effect which occurs because ascorbate-dependent enzyme reactions continue for 24-48 hours after intake is lowered, and use up vitamin C which is not being replenished. The effect is to lower one's serum vitamin C blood concentration to less than normal for a short amount of time. During this period of time there is a slight risk of cold or flu infection through reduced resistance. Within a couple of days the enzyme reactions shut down and blood serum returns to the normal level of someone not taking large supplements. This is not scurvy, which takes weeks of zero vitamin C consumption to produce symptoms. It is something people who take large vitamin C supplements need to be aware of in order to gradually reduce dosage rather than quit taking Vitamin C suddenly. (ref.6 para 4) This is a theoretical risk for those taking supplements - e.g. if they find themselves severely ill, and in a hospital without the supplements, at a time when they need normal or better levels of vitamin C to fight the disease (ref.[4] and search for "The major problem"). At this time, many doctors and hospital staff do not know much about nor administer megadosing of supplements, so that patients may have to rely on friends or relatives to bring them their supplements.
Some writers [15] have identified a theoretical risk of poor Copper absorption from high doses of Vitamin C, although little experimental evidence supports this. However, ceruloplasmin levels seem specifically lowered by high vitamin C intake. In one study, 600 milligrams of Vitamin C daily did not decrease copper absorption or overall body copper status in young men, but led to lower ceruloplasmin levels similar to those caused by copper deficiency [16]. In another, ceruloplasmin levels were significantly reduced [17].
There are stories circulating among some folk remedy proponants that doses of around 12 grams per day of Vitamin C can induce an abortion in women under 4 weeks of pregnancy. [18] This is not supported by scientific research however. [19]
Recent studies into the use of both Vitamin E and C as possible help in preventing oxidative stress leading to pre-eclampsia has failed to show any benefit,[20] but did increase the rate of babies born with a low birthweight in one study.[21]
[edit]
Sources of vitamin C
Vitamin C is obtained through the diet by the vast majority of the world's population. The richest natural sources are fruits and vegetables, and of those, the camu camu fruit and the billygoat plum contain the highest concentration of the vitamin. It is also present in some cuts of meat, especially liver. Vitamin C is the most widely taken nutritional supplement and is available in a variety of forms from tablets and drink mixes to pure ascorbic acid crystals in capsules or as plain powder.

[edit]
Plant sources

Rose hips are a particularly rich source of vitamin CCitrus fruits (orange, lemon, grapefruit, lime), tomatoes, and potatoes are good common sources of vitamin C. Other foods that are good sources of vitamin C include papaya, broccoli, brussels sprouts, black currants, strawberries, cauliflower, spinach, cantaloupe, kiwifruit, cranberries and red peppers.

Emblica officinalis often referred to as Indian gooseberry, is one of the richest known sources of vitamin C (720 mg/100g of fresh pulp or up to 900 mg/100g of pressed juice.)– it contains 30 times the amount found in oranges.

The amount of vitamin C in foods of plant origin depends on:

the precise variety of the plant,
the soil condition
the climate in which it grew,
the length of time since it was picked,
the storage conditions,
the method of preparation. Cooking in particular is often said to destroy vitamin C - but see the section on Food preparation.
The following table is approximate and shows the relative abundance in different raw plant sources. The amount is given in miligrams per 100 grams of fruit or vegetable (in comparison, one teaspoon of pure vitamin C weighs 4,500 miligrams)...

Plant source Amount
Billy Goat plum 3150
Camu Camu 2800
Wolfberry 2500
Rose hip 2000
Acerola 1600
Amla 720
Seabuckthorn 600
Jujube 500
Baobab 400
Blackcurrant 200
Red pepper 190
Parsley 130
Guava 100
Kiwifruit 90
Broccoli 90
Loganberry 80
Redcurrant 80
Brussels sprouts 80
Lychee 70
Persimmon 60
Papaya 60
Plant source Amount
Strawberry 60
Orange 50
Lemon 40
Melon, cantaloupe 40
Cauliflower 40
Grapefruit 30
Raspberry 30
Tangerine 30
Mandarin orange 30
Passion fruit 30
Spinach 30
Cabbage raw green 30
Lime 20
Mango 20
Melon, honeydew 20
Tomato 10
Blueberry 10
Pineapple 10
Pawpaw 10
Grape 10
Plant sour