【編者按】

        黃金大米在中國引發(fā)過較大關(guān)注。2008年6月，一支由中美科學(xué)家組成的科研團隊在湖南衡陽的一所小學(xué)進行了相關(guān)實驗，25名小學(xué)生在未告知黃金大米轉(zhuǎn)基因的情況下，食用了黃金大米。2012年8月，該研究被國際環(huán)保組織綠色和平曝光，引發(fā)社會關(guān)注。中國疾控中心經(jīng)調(diào)查發(fā)現(xiàn)，實驗存在違規(guī)之處，這引發(fā)了民眾對轉(zhuǎn)基因、黃金大米安全性的進一步疑慮。

        2014年10月，在中國科學(xué)院與美國科學(xué)院共同主辦的“全球轉(zhuǎn)基因農(nóng)作物發(fā)展現(xiàn)狀和未來展望國際研討會”上，來自10個國家的18名全球生物技術(shù)研發(fā)領(lǐng)域的專家出席了會議，并發(fā)表了關(guān)于轉(zhuǎn)基因達(dá)成的8點共識，其中包括用于特定作物改良的轉(zhuǎn)基因方法對人和動物沒有任何負(fù)面影響、黃金大米是營養(yǎng)加強的轉(zhuǎn)基因作物，對維生素A缺乏癥提供了一種干預(yù)方法等。

       10月24日，澎湃新聞（m.dbgt.com.cn）在上海采訪了參加會議的黃金大米人道主義委員會執(zhí)行秘書、黃金大米工程負(fù)責(zé)人Adrian Dubock博士，并在此后半個月里，就一些技術(shù)問題以及觀點對其進行了郵件采訪，現(xiàn)將其對黃金大米、轉(zhuǎn)基因技術(shù)的介紹以及對一些反轉(zhuǎn)基因組織的評價以來信的方式展示。英文原文附于文末。

        

        維生素A缺乏癥是兒童失明的主要原因，每年全球有近50萬兒童受此困擾，如果在之后的一年里狀況沒有好轉(zhuǎn)，其中一半的兒童會因此死亡。更重要的是，最近20年的研究發(fā)現(xiàn)，VAD是一種營養(yǎng)獲得性免疫缺陷綜合癥?；加蠽AD的兒童或孕婦免疫力會減弱，難以抵抗疾病，一些對正常人而言常見的疾病對于VAD患者可能是致命的。充足的維生素A能預(yù)防全球范圍內(nèi)23% - 34%的5歲以下兒童的死亡率以及40%的孕婦死亡率。

        在中國的城市和農(nóng)村，VAD同樣常見。2004年，3-12歲中國兒童維生素A缺乏率為9.3%，其中城市為3.0%，農(nóng)村為11.2%。中國維生素A邊緣缺乏率為45％，其中城市為29%，農(nóng)村為50%。2006年的一項調(diào)查顯示，VAD在中國6歲以下兒童的感染率為12.2%，其中嚴(yán)重缺乏維生素A的比率為0.5%。那些住在貧困山區(qū)、母親受教育程度低、少數(shù)民族的兒童患VAD的風(fēng)險更大。在回顧2005年之前10年的數(shù)據(jù)后，WHO于2009年的一份報告稱，VAD是中國孕婦面臨的一個極其嚴(yán)重的公共安全問題。

        只有動物和人能夠合成維生素A。一份理想的營養(yǎng)均衡的膳食包括肉類、奶類以及果蔬類。植物中有色部分中的化學(xué)成分能被人體用于合成維生素A，而從動物類食物中，人體可以直接攝取維生素A。但不是每個人都能吃得起肉，而一般來說，人體從植物中提煉維生素A的效率較低。一個1~3歲的兒童每天需要8份深色綠葉蔬菜才能達(dá)到維生素A的推薦膳食供給量，鑒于食用植物合成維生素A的效率如此之低，那些貧困兒童難以通過蔬果的攝入補充足夠的維生素A。

        1990年代初期維生素A膠囊被發(fā)明，可以一年兩次為維生素A缺乏的地區(qū)居民提供補充，但VAD最直接的受害者：兒童，卻不是膠囊補給的受益者。因為擔(dān)憂可能的毒性，這些膠囊不會給兒童食用。此外，這些膠囊需要付費購買，將其運輸過去也需要費用，并聯(lián)系相關(guān)人員。

        在當(dāng)時，普及維生素A膠囊也是有爭議的事情。但不管怎樣，這種膠囊在過去25年間挽救了成千上萬人的生命。然而，上述其面臨的困境使其難以持續(xù)，這導(dǎo)致VAD每天仍能奪取6000多兒童的生命，這個問題需要聯(lián)合國或相關(guān)國家用下一個25年來解決。

        VAD通常與貧困有關(guān)，尤其是過度依賴碳水化合物，其不含有能在人體內(nèi)轉(zhuǎn)化為維生素A的有色物質(zhì)。一個典型的例子是大米，大米是很好的能量來源，但不含維生素A或鐵等微量元素，在一些以大米為主食的地區(qū)，大米能占日常飲食的80%以上。此外，大米也一直是最便宜的食物。

        黃金大米是第一個有針對性的設(shè)計出的食品，用以對抗VAD，其原理是往水稻里插入一段從玉米中提取出的基因。黃金大米被食用后能在人體內(nèi)轉(zhuǎn)變?yōu)榫S生素A，其實可以將其稱為最終的“有機作物”，因為水稻本身成為了維生素A的前體：β-胡蘿卜素的來源，這一成分不僅只是在水稻的葉子中，而同樣在水稻的谷子里，在食用部分里。

        2004年，在英國的一個實驗室里，研究者用轉(zhuǎn)基因技術(shù)成功創(chuàng)造了黃金大米。此后，黃金大米的培育均是通過傳統(tǒng)育種手段來實現(xiàn)。研發(fā)人員已經(jīng)捐贈了這一技術(shù)，供各國政府利用。黃金大米項目是非營利的，沒有一個人，也沒有一個組織，會因為推廣黃金大米而從中牟利。

        2001年時，長期反對轉(zhuǎn)基因技術(shù)的國際環(huán)保組織綠色和平組織聲稱，乳母食用18公斤烹飪好的黃金大米（相當(dāng)于6.3公斤干重的大米）才能補充足夠的維生素A。這是一派胡言。首先，當(dāng)時研究才剛剛開始，要食用多少才能補充足夠沒人能知道；其次，合理的估計（事后也得到證實）顯示黃金大米可以成為維生素A的有效來源。

        隨后黃金大米進入了實驗階段，先在美國用成人參與實驗，后在中國用兒童參與實驗。在中國的實驗是由湯光文博士和她的合作者操作的，湯光文本人是華裔。這一實驗在2003年就精心策劃好了，于2008年完成。與普通大米相比，黃金大米唯一的不同是多了β-胡蘿卜素。食物中（包括黃金大米）所含的β-胡蘿卜素的劑量對人體是安全的，而如果人體過量攝入，也不會轉(zhuǎn)變?yōu)楦嗟木S生素A，而是會將其排出。

        2008年在湖南衡陽的黃金大米實驗并不是安全性實驗，其安全性實驗早已在美國完成。涉及人體的實驗，尤其是涉及到兒童，不管是在美國、中國還是其他國家，都是被嚴(yán)格控制的。

        這項研究用了非常巧妙的辦法來分析β-胡蘿卜素轉(zhuǎn)化為維生素A的效率，其利用的是一小份血樣。研究結(jié)果很令人滿意：“就β-胡蘿卜素轉(zhuǎn)化效率而言，黃金大米比食用油、菠菜更高，一碗100~150克烹飪過的黃金大米（50克干重）可以提供給6~8歲的中國兒童60%的推薦攝入量”，“在補充維生素A上，在以大米為主食的區(qū)域，黃金大米能起到和肉蛋果蔬一樣的效果”。這些評語均引自湯光文發(fā)表于2012年8月的論文。顯然，2001年時綠色和平關(guān)于食用量的說法是錯的。此外，綠色和平出于反對一切轉(zhuǎn)基因的目的，還詆毀2008年衡陽實驗杰出的實驗結(jié)果，這一結(jié)果由湯光文及其合作研究者與一些中國家庭合作得出。

     2012年8月30日，綠色和平組織在中國發(fā)布了一份通稿，這份通稿是從遠(yuǎn)在德國的計算機服務(wù)器發(fā)出的，這份通稿稱“這一實驗不可能沒有違反科學(xué)和醫(yī)學(xué)倫理，而且還欺騙中國政府稱其叫停了研究”。這一新聞稿誤導(dǎo)了中國民眾。從實驗結(jié)束的2008年到2012年間，綠色和平?jīng)]有一點動作，倒是在2年之后突然質(zhì)疑，讓受試兒童及其家長開始擔(dān)憂。他們的擔(dān)憂又與媒體或社交媒體的關(guān)注呼應(yīng)，最后使得這個議題在微博上火了好幾周。

        事實上，只有三分之一的受試兒童吃過黃金大米，并且只吃過一次。其食用的黃金大米含有的β-胡蘿卜素約等于一小塊胡蘿卜。

        因此不難理解，英國環(huán)境、食品與農(nóng)業(yè)事務(wù)部國務(wù)大臣Owen Paterson將綠色和平組織反對黃金大米的行為稱之為“邪惡”。此外，綠色和平組織的聯(lián)合創(chuàng)始人Patrick Moore后來在1970年代離開了這一組織，如今他將該組織反對黃金大米的行為視為“反人類罪”。有個網(wǎng)站（www.allowgoldenricenow.org）在講這個事情，你們可以去看看。

        Letter from Dr.Adrian Dubock

        According to the data of World Health Organisation, VAD is very common, it affects 250 million children globally, and a significant number of pregnant women too.

        Vitamin A deficiency is the leading cause of childhood blindness globally, with up to half a million children affected each year, or which half of them die within 12 months if the condition is not treated. Even more important, and only recognised in the last 20 years, is that vitamin A deficiency is a nutritionally acquired immune deficiency syndrome. Children and mothers with insufficient vitamin A in their diets lose the protection of their normal immune defences against common or uncommon diseases. Diseases which should be survivable in well-nourished people become lethal. A universal source of vitamin A will prevent 23 – 34% of total under 5 years’ child mortality globally, and up to 40% maternal mortality.        

        Vitamin A deficiency in China

        Vitamin A deficiency is a common nutritional problem in China among the urban and rural populations. In 2004, the prevalence of vitamin deficiency among children of 3 to 12 years old was 9.3%: in the urban areas 3.0% and in rural areas 11.2%. The prevalence of marginal vitamin A deficiency was 45% of the whole population: with 29% in urban and 50% in rural areas. A 2006 survey found VAD affecting 12.2% of Chinese children 0 – 6 years, and severe VAD afflicting 0.5% of the same age group. Chinese children living in the poor western area having a mother with either poor education or of minority ethnicity have a high risk of VAD. Reviewing a decade’s data up to 2005, the World Health Organisation in 2009 reported that vitamin A deficiency was a severe public health problem for pregnant women in China.        

        Only animals and humans can make vitamin A. A balanced diet including animal products such as eggs, milk, butter, cheese and liver as well as coloured fruits and vegetables is ideal. The human body makes vitamin A from the chemicals in the coloured parts of plants we eat. Animal products eaten by humans provide actual vitamin A. But many people cannot afford to eat animal products. Normally the conversion efficiency from plants sources of vitamin A is very poor too.        

        “A young child between ages one year and three would need to eat eight servings of dark green leafy vegetables per day in order to meet the Recommended Dietary Allowance for vitamin A. The problem of the low bioavailability of vitamin A in plant foods has brought the sobering reality of the virtual impossibility for most poor, young children to meet their vitamin A requirements through vegetable and fruit intake alone. The low bioavailability of vitamin A from plant foods explains, in part, the presence of vitamin A deficiency among children living amid ample supplies of dark green leafy vegetables and other plant sources of vitamin A”.        

        Since the early 1990’s vitamin A capsules have been provided, ideally twice a year, in many places where the population suffers from vitamin A deficiency. But the capsules cannot be taken by the most vulnerable to the deficiency, very young children, because of toxicity concerns. The capsules have to be paid for, they have to be distributed which also costs money, and the relevant people have to be in contact. At the time of their introduction the use of vitamin A capsules was controversial. Undoubtedly however vitamin A capsule programmes have saved millions of lives in the last 25 years. But for the above reasons the programmes are unsustainable. And vitamin A deficiency remains problematic killing around 6000 under 5 years’ old children every single day that the United Nations and national governments have tried to overcome it for the same 25 years.        

        Vitamin A deficiency is often associated with poverty, and especially an overdependence in the diet of a carbohydrate rich food, without any of the coloured chemicals which the human body can turn into vitamin A. A good example is white rice: a good source of energy, but with no pro-vitamin A or other essential micronutrients, such as iron. In some rice consuming populations rice constitutes 80%+ of the daily diet. And as food prices increase the percentage of rice increases as it remains the cheapest.        

        Golden Rice        

        Golden Rice is the first purposefully designed food designed to be of assistance as an additional intervention to combat vitamin A deficiency. By inserting one gene from yellow maize, and one from a very commonly ingested by humans soil bacterium, the rice has been induced to make the coloured chemical which humans can turn into vitamin A when eaten. It is the ultimate ‘organic crop’: the rice plant itself makes the beta-carotene source of vitamin A, not just in the leaves as in a white rice plant, but also in the rice grain itself, the only part which is consumed by man.        

        The genetic modification which created Golden Rice occurred once, in a laboratory in UK, in about 2004. Since then only conventional breeding systems have been used to multiply the rice. The inventors have donated the nutritional technology free of any charge to governments who want to breed it into the rice varieties their people like to eat, and which grow well in their countries. The project is not-for-profit. No one, and no organisation, involved in the development of Golden Rice will gain financially from adoption of the nutritional technology or not.        

        Human Research and Greenpeace opposition        

        In 2001 Greenpeace, the political activist group already long opposed to any use of GM-technology in crop breeding, claimed that a breast-feeding woman would have to eat at least 6.3 kg of uncooked Golden Rice, nearly 18 kg of cooked rice, daily to obtain any benefit from it.'        

        This outrageous claim, the first of many, was without justification. At the time shortly after research had started, in the absence of human data, no one knew how much would be needed. Rational estimations were however much more realistic: it was expected, but at the time not known, that Golden rice could provide a useful source (beta-carotene) of vitamin A in the human diet.    

        Following similar research in USA with adults and Golden Rice, and in children in China with other plant sources of pro-vitamin A, Chinese born Dr Guangwen Tang and her mostly Chinese co-investigators undertook research with Golden Rice, spinach and beta-carotene (the coloured chemical) in oil and Chinese children. The field research, initially carefully planned in 2003 was completed in 2008. The only difference between Golden Rice and white rice is that Golden Rice contains beta-carotene. At the levels found in food, including Golden Rice, beta-carotene is safe. The human body excretes, and does not convert to vitamin A, what it does not need.        

        The Chinese research conducted with the full cooperation of families and a school in Hengyang in 2008 was not a safety test; safety was already established, and human research, especially research involving children, is very tightly controlled in both China and USA and other countries.        

        The research used very sophisticated methods of analysis of very small samples of blood to understand how efficiently the beta carotene was converted to vitamin A. The results were spectacularly good: ‘’The b-carotene in Golden Rice is as effective as pure beta-carotene in oil and better than that in spinach at providing vitamin A to children. A bowl of about 100 to 150 g cooked Golden Rice (50 g dry weight) can provide about 60% of the Chinese Recommended Nutrient Intake of vitamin A for 6–8-y-old children’’. “GR may be as useful as a source of preformed vitamin A from vitamin A capsules, eggs, or milk to overcome VAD in rice-consuming populations. Awareness of the vitamin A equivalence of plant foods provides a scientific basis for designing food-based nutritional programs to improve vitamin A status in many regions of the world where VAD is still common.” Both these quotes are from the scientific paper reporting the 2008 research with Chinese children published online on 8th August 2012. Clearly Greenpeace were very wrong in 2001, and had every reason (from their political perspective of opposing all gm-crops) to try and discredit these excellent 2012 results of Tang and her co-investigators obtained through the 2008 cooperation of Chinese families!        

        On 30th August 2012, Greenpeace from their German computer server issued a press release in China: “This study could not have taken place without a serious breach of scientific and medical ethics, and goes against a Chinese government decision to abort plans for the trial.” This Greenpeace press release misinformed the Chinese people, and having had zero reported issues in the official 2 years follow up of the research in 2008 to 2010, suddenly the parents of the children involved in the research became concerned. Their concern was echoed by social media, and the press, and the hysteria which developed caused the issue to be the most widely commented upon on Wei-bo for a couple of weeks.        

        In fact, one third of the children involved had consumed, on one occasion only, one small serving of Golden Rice containing approximately the same amount of beta-carotene as in a small carrot.        

        It is understandable that a UK Government Minister, Owen Paterson, responsible for Food, the Environment and Rural Affairs has called Greenpeace “Wicked” for their opposition to Golden Rice. Similarly, Patrick Moore, the co-founder of Greenpeace in the 1970’s left the increasing ‘a(chǎn)nti-human’ Greenpeace organisation and has accused them of crimes against humanity, for their opposition to Golden Rice (see: www.allowgoldenricenow.org )