限制蛋氨酸摄取来饿死癌细胞
本视频由 Michael Greger 医生于2013年9月18日制作，来自NutritionFacts.org。
译者前言：译文中没有包括视频中全部幻灯片，请观看完整视频。并请阅读：你可能想不到最常见蔬食中就含有8种必需氨基酸，较全面地了解氨基酸和蛋白质以更好地理解本文。
摘要：蛋氨酸限制 — 通过采取植物性饮食可以达到最佳的蛋氨酸限制 — 可能证明对癌症病人有重大影响，因为与正常组织不同，很多人类肿瘤需要蛋氨酸才能生长。
举个例子，在设计抗生素时，你不会制造一种破坏 DNA 的药物，因为这是人类和细菌共有的东西。它会杀死细菌，那没关系，但它也可能会杀了我们。
In designing an antibiotic, you couldn’t create a drug that destroyed DNA, for example, because that’s something that both humans and bacteria share in common. It would kill bacteria, all right, but it might kill us, too.
所以，许多抗生素产生作用是通过攻击细菌细胞壁 — 细菌有，但我们没有的东西。
So, many antibiotics work by attacking the bacterial cell walls — something bacteria have, that we don’t.
抗真菌剂可攻击真菌的独特细胞壁。农药可以通过攻击昆虫特殊的外壳来发挥作用。
Antifungals can attack the unique cell walls of fungus. Pesticides can work by attacking the special exoskeleton of insects.
但是，战胜癌症更困难，因为癌细胞是我们自己的细胞。因此，抗击癌症归结为寻找和利用癌细胞和正常细胞之间的差异。
But, fighting cancer is harder, because cancer cells are our own cells. So, fighting cancer comes down to trying to find and exploit differences between cancer cells and normal cells.
四十年前，一篇里程碑式的论文首次发表，显示许多人类癌症具有所谓的绝对蛋氨酸依赖性，就是说你可以在培养皿中培养正常细胞而不用给它们蛋氨酸。“正常细胞茁壮成长。”
Forty years ago, a landmark paper was published showing for the first time that many human cancers have what’s called absolute methionine dependency, meaning you can grow normal cells in a petri dish without giving them the amino acid methionine. “Normal cells thrive.”
但是，没有蛋氨酸，癌细胞就会死亡。例如，正常的乳房细胞， 无论有无蛋氨酸都会正常生长。
But, without methionine, cancer cells die. Normal breast cells, for example, grow no matter what — with or without.
但是，这里是白血病细胞，他们需要额外添加蛋氨酸才能生长，否则就死翘翘啦。
But, here’s leukemia cells, they need that extra added methionine to grow, or they just flatline.
癌细胞利用蛋氨酸作什么呢？肿瘤利用蛋氨酸会产生“气态含硫化合物”，经过专门训练的诊断犬实际上可以甄别出来。
What does cancer do with the methionine? Tumors generate “gaseous sulfur-containing compounds” with it, that specially trained diagnostic dogs can actually pick up.
有嗅痣犬可以挑选出皮肤癌[患者]。
There are mole-sniffing dogs that can pick out skin cancer.
有嗅呼吸犬可以挑选出肺癌患者。
There are breath-sniffing dogs that can pick out people with lung cancer.
嗅尿犬可以诊断膀胱癌。而且，是的，你猜对了...嗅屁犬可以诊断结肠直肠癌。
Pee-sniffing dogs that can diagnose bladder cancer. And, yes, you guessed it, fart-sniffing dogs for colorectal cancer.
医生现在可以将他们的“实验室”带到实验室。为术语“宠物扫描”提供了全新的含义。
Doctors can now bring their Lab to the lab. Gives a whole new meaning to the term “pet scan.”
无论如何，蛋氨酸依赖不仅存在于培养皿中的癌细胞系中。
Anyway, methionine dependency is not just present in cancer cell lines in a petri dish.
取自患者的新鲜肿瘤显示许多癌症似乎有生化缺陷，这使他们有蛋氨酸依赖性，“包括一些结肠，乳房，卵巢，前列腺和皮肤肿瘤。”
Fresh tumors taken from patients show that many cancers appear to have biochemical defects that makes them methionine-dependent — “ including [some] tumors of the colon, breast, ovary, prostate, and [skin].”
化学公司正在争取成为第一个推出“蛋氨酸耗竭药物”的公司，但是，由于“蛋氨酸主要来源于食物”，更好的策略可能是通过降低蛋氨酸摄入量来降低蛋氨酸水平 — 完全不吃用于控制癌症生长的高蛋氨酸食物。
Chemo companies are fighting to be the first to come out “methionine-depleting drugs,” but, since “methionine is sourced mainly from food,” a better strategy may be to lower methionine levels by lowering methionine intake — eliminating high-methionine foods for cancer growth control.
有这样的想法；看这。“戒烟，食用富含植物的饮食，和其他生活方式措施可以预防大部分癌症。”
Here’s the thinking; look. “Smoking cessation, consumption of diets rich in [plants],…and other lifestyle measures can prevent the majority of cancers.”
不幸的是，人们不会这样做，并且，“因此，每年都有数十万美国人患上转移性癌症。
Unfortunately, people don’t do them, and, “as a result, each year, hundreds of thousands of Americans develop metastatic cancer.
化疗仅能治愈少数类型的转移性癌症......不幸的是，绝大多数常见转移性癌症（如乳腺癌，前列腺癌，结肠癌和肺癌）都是致命的。
Chemo therapy cures only a few types of metastatic cancer…Unfortunately, the vast majority of common metastatic cancers…[like breast, prostate, colon, and lung] are lethal.
因此，我们迫切需要治疗转移性癌症的新策略。而膳食蛋氨酸限制可能就是这样一种策略。
We therefore desperately need novel treatment strategies for metastatic cancer. Dietary methionine restriction may be one such strategy.”
那么，蛋氨酸在哪里呢？
So, where is methionine found?
蛋氨酸特别存在于鸡肉和鱼肉里。牛奶、红肉和鸡蛋里含量少些[比鸡和鱼]。
Particularly chicken, and fish. Milk, redmeat, and eggs have less.
但是，如果你真的想只吃低蛋氨酸食物，那就是水果，坚果，蔬菜，谷物和豆类。
But, if you really want to stick with lower methionine foods, fruits, nuts, veggies, grains, and beans.
换句话说，“采用主要吃纯素饮食可以实现蛋氨酸限制”。
In other words, “methionine restriction may be achieved using a predominately vegan diet.”
那么，为什么不是每个肿瘤科医生都这样做？
So, why isn’t every oncologist doing this?
“尽管近年来许多有前途的临床前和临床研究，饮食蛋氨酸限制和其他癌症治疗饮食方法尚未获得广泛的[传播]临床应用。
“Despite many promising preclinical and clinical studies in recent years, dietary methionine restriction and other dietary approaches to cancer treatment have not yet gained wide [spread] clinical application.
大多数临床医生和研究人员可能不熟悉癌症的营养疗法。 [啊，这是轻描淡写。]
Most clinicians and investigators are probably unfamiliar with nutritional approaches to cancer. [Ah, that’s an understatement.]
由于它已被检验了几十年，许多其他人可能会认为氨基酸限制是一种“旧想法”。
Many others may consider amino acid restriction as an ‘old idea,’ since it has been examined for several decades.
“然而，许多好的想法在临床上证明有价值前，如果不是几个世纪，也被埋没了数十年…随着进一步研究，饮食中的蛋氨酸限制，单独或与其它疗法相结合也许会证明对癌症患者产生重大影响。”
However, many good ideas remain latent for decades if not centuries before they prove valuable in the clinic…With the proper development, dietary methionine restriction, either alone or in combination with other treatments, may [also] prove to have a major impact on patients with cancer.”
译者注：虽然蛋氨酸是人体必需氨基酸之一，但我们平时经常吃的最普通的食物都含有足够的蛋氨酸，所以无需担心蛋氨酸会缺乏，我们要担心的是蛋氨酸太多。
下表列出了世界卫生组织（WHO）推荐的8种必需氨基酸含量，如果我们只吃其中一种食物，总热量吃够2200卡路里时，8种必需氨基酸及蛋白质含量：
参考资料：世界卫生组织（2007）人类营养中蛋白质与氨基酸需求量：
World Health Organization.(2007). Protein and Amino Acid Requirements in Human Nutrition: Report ofa Joint WHO/FAO/UNU Expert Consultation. Retrieved from:
http://whqlibdoc.who.int/trs/WHO_TRS_935_eng.pdf.
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