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【伪科学】:
吃虾+橙汁=中毒?专家:不可信!

【发布日期:2015年7月20日】
最近短信频传:吃虾+橙汁=中毒?

这个2001年老掉牙的伪科学传闻,至今还在网络流传。

吃虾+橙汁(维他命C)=“砒霜”=中毒?专家说:不可信!

听听人们怎么解释:



新闻辟谣:



新闻辟谣:





网络里的一些真相文字记录:

流言粉碎机:

“维生素C与虾不能同吃”?

来源:科学人

2010-12-14 16:26

流言:

台湾,一名女孩突然七孔流血暴毙。经初步验尸,断定为因砒霜中毒而死亡。一名医学院的教授被邀赶来协助破案。他仔细地察看了死者胃中取物后说:“砒霜是在死者腹内产生的。”死者生前每天会服食“维他命C”,晚餐又吃了大量的虾。问题就出在这里!

美国芝加哥大学的研究员通过实验发现,虾等软壳类食物含有大量浓度较高的五钾砷化合物。这种物质食入体内,本身对体并无毒害作用。但在服用维生素C之后,由于化学作用,使原来无毒的五价砷,转变为有毒的三价砷,又称为三氧化二砷,这就是们俗称的砒霜!故中其毒而死者,常是七窍出血。所以;为慎重起见,在服用维生素C期间,应忌食虾类。

真相:

砒霜确实是三价砷,维生素C也确实是还原剂,把五价还原成三价也是听起来合理的反应。对大部分高中毕业之后就没有接触过化学教育的人来说,这样的表述杀伤力确实很大。难怪这一流言的原型自2001年5月现之后[1],至今仍然在互联网的各个角落活跃着。

海鲜里的砷主要以有机砷的形式存在,无机砷的含量在海鲜里最多不超过总砷含量的4%,其中多是五价砷,少量是三价砷。而占主体地位的有机砷的危害非常之小,绝大部分以砷甜菜碱(arsenobetaine)的形式存在,它们基本上会被原封不动地排出体外[2]。如果要在这个问题上较真,我们反而应该担心包括大米和面粉在内的谷物产品,它们提供了我们日常饮食中大部分的无机砷[3]。由此可见,假如维生素C真能轻而易举地还原五氧化二砷从而让人中毒,那你该考虑的就不止是“吃不吃虾”的问题,而是“吃不吃饭”的问题了。

还好,我们似乎并未听说过有人因为吃“维生素C+大量米饭”而死的。除了流言中那个语焉不详的案例,我们也从没听说过因为吃“维生素C+大量虾”而中毒的。事实上,迄今为止(原文数据截至2006年底),尚未见一例被认为与鱼虾有关的砷中毒病例。[2]

关于“五价砷能不能在体内被维生素C还原为三价砷”的问题,存在一些讨论。不过,即使不考虑这个问题,也不难发现这个流言的可笑之处。假设人体是这个还原反应的绝佳场所,被吃进肚子里的五价砷一点不浪费的全部还原得到了三价砷。那么一个人要吃多少虾才足以中毒呢?

根据我国国家标准GB2762-2005,虾蟹类无机砷的上限是0.5mg/kg鲜重。也就是每千克鲜虾中,含无机砷不能超过0.5毫克。对于健康的成年人来说,砒霜的经口致死量约为100~300mg。按100mg砒霜来算,其中含有的砷元素为75mg(100mg*150/198)。假设流言中的受害者吃的全都是污染较重的,达到无机砷含量上限的虾,那么,她也需要吃下整整150公斤(75mg/0.5mg/kg)的虾,才足以“保证”被砒霜毒死。即使按照砒霜中毒下限5mg,食用的虾无机砷超标十倍来计算,那起码也得0.76千克的虾才足以被还原出来。对于一个小女生来说,通过这样的方式出现砒霜中毒反应之前,她也撑坏了。

结论:谣言破解。

这个谣言是用低级的化学知识来吓唬人的杰作。虾里的无机砷含量很低,就算是能被维生素C还原得到砒霜,那么微小的量,连中毒反应都不会出现,更别说是“暴毙而死”了。

延伸阅读:

详细资讯请见 《借我一双慧眼吧:虾和Vc的八卦恩怨》 ,Ent,科学松鼠会
松鼠田不野 《稻砷案》

参考资料:

[1] 网页:snopes
[2] PDF文件:Seafood arsenic: Implications for human risk assessment. Regulatory Toxicology and Pharmacology 47 (2007) 204–212.
[3] 松鼠田不野 《稻砷案》
[4] 半数致死量:描述有毒物质的常用指标,引起一半实验对象死亡的剂量。

2014.5 更新:

我搜索到了一篇来自1985年的文献,这是已知唯一一篇专门讨论Vc和海鲜同食的文献,但是因为年代久远,没有能找到它的全文,只有报纸对它的报道。

根据报道来看,文献认为Vc还原五价砷为三价是可能发生的反应,但其剂量根本不可能当时中毒致死。作者关注的是这一反应是否会导致长期致癌风险。

不过这一研究并没有后续,因为如上所述,今天我们知道虽然虾的含砷量很高,但几乎都是有机砷,和Vc不反应。而无机砷的主要摄入来源是大米、面粉等谷物。就算要关注它,考虑的也是Vc和饭是否能同食……

这篇论文是伊利诺伊大学的研究者做的,芝加哥的报纸对其进行了报道。这可能是流言误为“芝加哥大学”的原因之一。



资源来源: Snopes.com

Claim: Vitamin C users who eat shrimp risk death from arsenic poisoning.

Examples:

[Collected via e-mail, 2001]

F.Y.I.

Spread this message out to as many friends and families as possible, because this is a matter of life and death!!

I just read a medical report from my friend saying that: DO NOT eat shrimp (Prawn) if you have just taken VITAMIN C pills!! This will cause you to DIE in ARSENIC (As) toxication within HOURS!!

THIS IS NOT A JOKE!! There's been a case happened in Taiwan.

Take care!

[Collected via e-mail, November 2011]

This is a story that happened to the relative of a friend of mine. If you love your family and your friends, just tell them about this story.

There was a woman who suddenly died with blood coming from her eyes, ear, mouth, nose, skin and tongue. After the authorities investigated, they claimed she died of food poisoning.

Before she died, she ate a lot of shrimp, but so did the rest of her family and they didn't die. It turns out that the problem was that she drank a liquid vitamin C supplement immediately after she ate the shrimp.

Basically, Shrimp contains an Arsenic Pentoxide (As2O5) and when she ate shrimp, she drank Vitamin C at the same time. This caused a chemical reaction in her stomach. The Arsenic Pentoxide (As2O5) in the shrimp become Arsenic Trioxide (As2O3), which was very poisonous. Her heart, liver, kidneys, and blood vessels failed, and she died from massive blood loss.

So, be careful if you eat shrimp. Wait a few hours before you take Vitamin C. Don't allow vitamin C and shrimp to occupy your stomach at the same time.

[Collected via e-mail, February 2014]

I can't believe it is true. The message goes with a teenager died suddenly with blood swell out of her mouth, nose, ears, and eyes. The autopsy found that the girl had consumed a lot of shrimps and took vitamin C at the same time before her death. The shrimp and vitamin C in her digestion system combined the arsenic chemical AsO5 from the shrimp and the acid from vitamin C to produce the fatal cyanide As2O3. So, beware, not to eat shrimp and vitamin C at the same time.



Origins:

Nearly all animals carry some form of arsenic in their systems, and seafood in particular is one of the primary food sources through which human beings ingest arsenic. However, the organic forms of arsenic found in natural food sources such as seafood are typically much less harmful than their inorganic counterparts, and one would generally have to ingest very large quantities of them over very long periods of time to suffer any significant ill effects. This e-mailed scare began circulating on the Internet in May 2001 presumably suggests that prawns metabolize a particular arsenic compound ordinarily non-toxic to humans, Shrimp but when the prawns are ingested in combination with Vitamin C, something in the vitamin prompts the formation of a different arsenic compound which is highly toxic to humans.

A study conducted back in 1985 did report that ingesting a combination of arsenic-bearing shellfish with high doses of Vitamin C could produce a toxic form of arsenic as described above through the reduction of arsenic pentoxide to arsenic trioxide:

Eating shellfish and popping huge doses of Vitamin C could prove lethal, say University of Illinois researchers who have made a surprising discovery about the nature of arsenic poisoning. The researchers in the university's animal sciences department in Champaign found that forms of arsenic usually considered harmless can become strongly poisonous through an interaction with Vitamin C. The unexpected finding by Gail Czarnecki, David Baker and John Garst concerns the way molecules of arsenic compounds are constructed. If atoms within the compounds share five electrons with neighboring atoms, they are said to be "pentavalent" and are fairly harmless. Several foods, especially shrimp and prawns, may contain high concentrations of such arsenic compounds. What the Illinois researchers found is that high doses of Vitamin C convert the pentavalent compounds into trivalent arsenic, a highly toxic poison. Cysteine, a chemical sometimes given as a treatment for heavy metal poisoning, also converts arsenic to the trivalent, highly toxic form.


The study did not find, however, that eating a single meal of shrimp in conjunction with taking an ordinary dose of Vitamin C was likely to cause one to keel over dead "within hours" from a fatal case of arsenic poisoning. The concern expressed was that, over a period of time, the repeated practice of eating arsenic-bearing shellfish while also taking megadoses of Vitamin C could result in chronic arsenic exposure leading to a increased risk of cancer. Nothing in the study found or suggested that a meal of shrimp and Vitamin C would cause one to "suddenly die with blood coming from your eyes, ear, mouth, nose, skin and tongue" — even if such a thing ever did happen, it must have occurred under very specific or extraordinary circumstances, or we'd be finding plenty of accounts of healthy-but-dead seafood lovers. We haven't turned up any news accounts of any death(s) occurring in Taiwan or elsewhere from this combination.

Barbara "arsenic and old plaice" Mikkelson

Last updated: 22 February 2014



同時吃蝦與維他命C會中毒?網路故事盛傳 飲食禁忌 專家嗤之以鼻

资源来源: 2009年05月22日 05:17 星島日報

  本報記者陸宜洛杉磯報道

  「一名台灣女子離奇死亡!原因是同時食用大量蝦子和維他命C,在體內形成砒霜,導致中毒而死。」這個從2001年就開始流傳的網路故事,雖經專家指證其不實謬論,但近日又被網友轉載,誤導許多平常有吃維他命的民衆不敢吃蝦。

  由於該網路故事言之鑿鑿,最初版本還指名道姓、連死者職業和背景都交代一清二楚;加上美國芝加哥大學研究人員的實驗佐證,蝦等軟殻類食物含有大量濃度較高的五鉀砷化合物,結合維他命C,的確會産生化學作用,將無毒的五鉀砷(As205)轉變為有毒的三鉀砷(As203),也就是俗稱的砒霜。

  而在2006年,版本還延伸成有人食用「檸檬蝦」後離奇死亡的勁爆文章,如今南加州華裔社區更接到翻譯成英文的版本,造成大衆對「服用維他命C應忌食蝦類」等説法深信不已。

  南加營養師劉宣宏分析,一般海産食物,蝦子等甲殼類的確含砷量較高,每1公斤約含42至174毫克,其中新鮮魚貝類會低些。而根據日本一項對三鉀砷的調查,日本人每日攝取三鉀砷量為0.1至1.22毫克,但以成人為例,引起中毒必須要達到體重每公斤5到50毫克的量,也就是位體重50公斤的成人,要攝取250至2500毫克的三鉀砷才會中毒。

  上述網路故事中的當事人,起碼吃下了6至14公斤蝦子(約220至512隻草蝦)才有可能中毒,一般人不可能一次吃到這麼多蝦子。劉宣宏表示,除非是大胃王比賽,否則很難在短時間內中毒,尤其人體擁有自我保護能力,對外來有毒物質入侵,腸胃道吸收能力會自行降低;另外,海鮮含有的砷多為「有機砷」,毒性低、容易從糞便排出體外,所以縱使食用1、2公斤的有機砷海鮮,中毒的可能性仍然不大。

  至於故事中引起化學反應的重要角色維他命C,劉宣宏指出,此種維他命為水溶性,在人體內代謝時間約為2小時,多會隨著尿液、汗水排出體外,且一般人每天可接受的攝取量為1萬毫克(約20片5百毫克維他命C);倘若在短時間內服用大量維他命C,人體還會自動藉著維他命C的酸性,加速腸胃道蠕動,造成腹瀉以排出體外。

  所以故事情節如果屬實,該女子得一次吃上幾百隻蝦子,還要在短時間內大量服用維他命C,並且沒有産生腹瀉等癥狀,才能讓體內的五鉀砷和維他命C起化學反應。

  香港浸會大學國際學院食物安全課程統籌劉信信也針對此故事作出評論,認為該化學反應可在實驗室裡出現,但在現實生活中,畢竟牽扯許多不定因素,不可能出現像實驗室同樣的條件,所以這種中毒現象要出現在人體其機會微之其微。



不要再传播下面这些似是而非文字了!拜托!
只要您上谷歌搜寻一下,就能知道其中的真相!
温馨提醒:不要再传播下面这些文字了:
【吃蝦的禁忌】

吃蝦的禁忌 請大家注意, 我有個在JKT的朋友, 吃了蝦,蟹再喝橙汁, 即刻走. ( 死) --現在很多飲料, 都有維他命C

我前天晚餐吃了一些蝦 ,回到家還好好的, 豈知吃了一粒 1000m g的維他命C, 馬上頭暈, 第二天上午還頭暈, 在床上休息一天才好.

一定要看!!

吃蝦的禁忌~~蝦+橙汁=死 ?

吃蝦的時候, 喝橙汁等於自殺

蝦>+ 維生素C = 砒霜------- > 女孩一夜暴斃臺灣

一名女孩突然無緣無故的七孔流血暴斃,一夜之間,就奔赴黃泉, 經過初步驗屍. 斷定為因砒霜中毒而死亡。 那砒霜從何而來?

一名醫學院的教授被邀趕來協助破案, 教授仔細地察看了死者胃中取物,不到半個小時, 暴斃之謎便揭曉。

教授說:死者並非自殺,亦不是被殺,而是死於無知的『它殺』」大家莫名其妙。教授說:「砒霜是在死者腹內產生的。」

死者生前每天也會服食「維他命C」,這完全沒有問題,問題出在 她晚餐吃了大量的蝦,吃蝦本身也是沒有問題的,所以她在家吃了都沒有事,但死者卻同時服用了「維他命! C」,問題就出在這!

美國芝加哥大學的研究員,通過實驗發現,蝦等軟殼類食物含有大量濃度較高的-五 鉀砷化合物。

這種物質食入體內,本身對身體並無毒害作用,但是,在服用「維生素C」之後,由於化學作用,

使原來無毒 的-五鉀砷 (即砷酸 酐,亦稱五氧化砷),其化學式為(As2O5),

轉變為有毒的三鉀砷 (即亞砷酸酐),又稱為三氧化二砷, 其化學式為(As2O3) ,這就是們俗稱的砒霜!

砒霜有原漿毒作用,能麻痹毛細血管,抑制巰基梅的活性,並使肝臟脂變肝小葉中心壞死,心、肝、腎、腸充血, 上皮細胞壞死,毛細血管擴張。

故中其毒而死者,常是七竅出血。

所以;為慎重起見,在服用維生素C期間,應當忌食蝦類。

看完後;請不要吝嗇,轉寄給你的同學和親友 --現在很多飲料, 都有維他命C。

給你自已&朋友正能量,請按「分享」!


温馨提醒:不要再传播上面这些文字了!








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