增肌与蛋白质的关系，运动员到底需要多少蛋白质？（上）
译者前言：还记得这两位医生吗？他们是一对夫妻，是《Keep It Simple, Keep It Whole》（保持简单，保持全食物）畅销书作者。
他们在这本书里的“食物健康程度评级表”得到坎贝尔博士的大力推荐，老玉米曾经在“何为低脂全蔬食饮食原则”的文章里翻译介绍给大家。
德国大学生丽萨刚刚用中文给大家详细解释了“食物健康程度评级表”的用法（点击阅读）。
他们在纪录片《餐叉胜于手术刀》中出现，并且是《餐叉胜于手术刀计划》作者，是新一代的非常棒的蔬食医生。
此演讲是康奈尔大学《蔬食营养》课的额外阅读资料（Bonus Resource)，虽然不属于正式课程内容，但非常值得一读。
此外，为更好地理解蛋白质，建议首先阅读 “ 你可能想不到最常见的蔬食中就含有8种必需氨基酸 ”，文章解释了 RDA 与 EAR 的关系，帮助理解蛋白质需求量 。
嗨，我是马特·莱德曼医生，一位经过认证的内科医生，专门从事营养和生活方式医学。
Hi, I’m Doctor Matt Lederman, a board-certified internist, who specializes in nutrition and life style medicine.
蛋白质是人们考虑转换为植物性饮食的一大问题。有时采用植物性饮食的运动员甚至更担心，所以我今天要试着解决一些这类问题。
Protein is a big concern for people thinking about converting to a plant-based diet. And sometimes even more of a worry for plant-based athletes, so I’m going to try and address some of those concerns here today.
简单的答案是我们每天获取太多蛋白质。
The short answer is that we get way too much protein per day.
事实上，我们最不需要担心的就是是否能获得足够的蛋白质。相反，我们应该关注我们摄取的蛋白质水平过高。这给我们的骨骼，肾脏和肝脏造成压力，因为这些器官会一直处在清理混乱中。与流行的观点相反，过量的蛋白质对运动员是不利的。
In fact, the last thing we need to worry about is not getting enough protein. Instead we should be concerned with the excessive levels of protein that we are getting. This stresses our bones, kidneys, and liver, as these are organs that get stuck cleaning up the mess. Contrary to popular belief, excess protein is not good for athletes.
1904年，耶鲁运动员了解到，将蛋白质摄入量降低至每天64克，运动表现提高35％，而他们开始吃的蛋白质超过100克。
In 1904, Yale athletes learned that decreasing protein intake to 64 grams per day, increased performance by 35%, and they were eating over 100 grams of protein to start with.
肌肉量是如何增加的呢？
How does muscle mass get built up?
部分原因在于基因，这部分是我们无法控制的。
It is partly genetics, which we have no control over.
部分原因在于激素，我们可以用药物来控制，例如类固醇和生长激素。
It is partly hormones, which we can manipulate with drugs, such as anabolic steroids and growth hormone.
还有部分原因在于肌肉负载的频率，比如举重，这是我们可以控制的。
And it is partly the frequency of which the muscle is loaded, such as weightlifting, which we do have control over.
所以这里的关键是，当我们做负重训练时，肌肉量会增加。
So the key here is that muscle mass is increased when we load it with weight.
一旦进行负重训练，肌肉扩张变大。所有肌肉都是如此。
Once loaded, the muscle hypertrophies, or enlarges. This happens to all muscles.
例如，这种情况心脏很常见。 当心脏在高血压情况下工作时，例如高血压的人，心脏中的肌肉会在一段时间后开始肥大或扩大。即使在没有补充额外蛋白质的人群中，心脏肥厚也会发生。
For example, it is very common in the heart. When the heart has to pump against high pressure, people with high blood pressure for example, the muscle in the heart starts to hypertrophy or enlarge after a period of time. And that hypertrophy happens even in people who do not supplement with extra protein.
出于某些原因，人们认为如果他们吃了大量的蛋白质，蛋白质就会被从肠道里推到二头肌中，但事实并非如此。
For some reason people think that if they eat tons of protein, it somehow gets pushed from their guts right into their biceps, but that is just not true.
事实上，在我的医学生物化学教科书中，它用粗体字表示：“成年人不能通过摄入过量的蛋白质来增加肌肉或其他身体蛋白质的数量。”然后它说：“如果饮食中摄取的蛋白质超过我们的需求，它被转化为糖原和甘油三酯，然后储存。”如果运动表现是一个问题，将过量的蛋白质转化为甘油三酯或脂肪引起我的担忧。
In fact, right in my medical biochemistry textbook it says in bold letters, “ Adults cannot increase the amount of muscle or other body protein by eating an excess amount of protein.” It then says, “ If dietary protein is consumed in excess of our needs, it is converted to glycogen and triacylglycerols, which are then stored. ” Converting excess protein to triacylglycerols or fat is concerning to me if performance is an issue.
此外，研究表明，增加蛋白质摄入量不仅没有帮助，而且可能有害。
Furthermore, studies show that increasing protein intake not only doesn’t help but can be harmful.
例如，一项研究表明，高蛋白饮食提供的碳水化合物不足以补充肌糖原，导致体液失衡和脱水。
For example, one study showed that high protein diets provided infufficient carbohydrates to replenish the muscle glycogen and resulted in fluid imbalances and dehydration.
另一项研究得出的结论是，由蛋白质而来的热量超过10％就足以将运动员，耐力跑步者置于正氮平衡状态。
Another study concluded that more than 10% of calories from protein was enough to put athletes, endurance runners, into positive nitrogen balance.
总之，随着摄取蛋白质的增加，不但没有益处，而实际上有潜在危害，。
In short, there was no advantage, and actually potential harm, with increasing protein consumption.
氮平衡是我们尝试估计需要多少蛋白质的一种方法。
Nitrogen balance is one way we try to estimate how much protein we need.
假设我们使用了所需要的所有蛋白质，并从尿液中的排出了多余的蛋白质，记住我们要避免摄取太多，因为分解和消除过量蛋白质的过程会对骨骼造成压力。
We assume we use all of the protein we need and eliminate the rest in our urine, and remember that we want to avoid having tons of excess because the process of breaking down and eliminating excess protein stresses our bones.
通过研究，我们可以通过测量氮平衡来看看我们是否摄取太少或太多的蛋白质。
In studies, we can measure our nitrogen balance to see if we are getting too little or too much protein.
研究人员寻找尿液中的氮。 我们使用氮测量氨基酸，因为氨基酸中含有氮。
Researchers look for nitrogen in the urine. We measure the amino acids using nitrogen because they have nitrogen in them.
一旦我们开始将氮排泄到尿液中，摄取更多的蛋白质有意义吗？
Does it make sense to consume more protein once we start spilling nitrogen into the urine?
那么这应该是我们的目标，只是刚好达到正氮平衡，然后就停在那里（停止摄取更多蛋白质）。请记住，就像热量一样，基于许多因素，包括运动、疾病等，您每天需要的蛋白质量会有所变化。 所以试图每天强迫自己摄取同样数量的蛋白质也不是一个很好的系统。
Well that should be our goal, to just barely achieve positive nitrogen balance and then stop there. And remember, just like calories, the amount of protein you need from day to day is going to vary somewhat, based on lots of factors, including exercise, illness, et cetera. So trying to force the same amount of protein into your diet each day is not a great system either.
此外，请记住，10％的热量来源于蛋白质足以在耐力运动员中实现正氮平衡，更不用说普通美国人了。它还表明，饮食中蛋白质的百分比较高，实际上降低了运动表现。
Also, remember that 10% of calories from protein was more than enough to achieve positive nitrogen balance in endurance athletes, let alone the average American. It also showed that higher percentages of protein in that diet, actually decreased performance.
这是有道理的，因为我们在食用足够量的蛋白质后所做的一切都是通过强迫身体消耗能量来消除所有过量蛋白质，从而给身体带来压力。
It makes sense because all we do after we consume adequate amounts of protein is stress our bodies by forcing them to expend energy to eliminate all of the excess protein.
事实是，根据世界卫生组织的说法，我们只需要约 5％ 的热量来自蛋白质。 而在 20 世纪 50 年代的研究表明，甚至比 5% 更少。
The truth is that according to the World Health Organization, we only need about 5% of our calories to come from protein. And studies back in the 1950s showed that we could get by with even less.
普通女性每天需要大约 30 克的蛋白质。 普通男性每天需要大约 40 克就能维持正氮平衡。
The average woman needs about 30 grams per day of protein. The average man needs about 40 grams per day to maintain positive nitrogen balance.
只要你从全食物中摄取足够的热量，那么你会得到所有你需要的蛋白质，注意加工食品如糖和油中不含蛋白质。
As long as you maintain sufficient calorie intake of whole foods, and note that processed foods like sugar and oil have no protein, then you’ll get all the protein you need.
事实上，如果你通过摄取全食物满足热量需求，每天少于30克的蛋白质是非常困难的。
In fact, if you meet your caloric needs with whole foods, it is very hard to get less than 30 grams of protein per day.
例如，如果你吃了 2000 卡路里的燕麦，你认为你会得到多少蛋白质？ 82 克。
For example, how much protein do you think you get if you eat 2,000 calories of oats? 82 grams.
我每天吃大约 3000 卡路里的热量，如果我只是吃了 3000 卡路里的玉米，我会得到多少蛋白质？ 80 克。
I eat about 3,000 calories per day, so how much protein would I get if I ate 3,000 calories of just corn? 80 grams.
即使只吃 2000 卡路里的西瓜，也有 40 克蛋白质。
Even 2,000 calories from watermelon alone has 40 grams of protein.
西兰花比牛肉含有更多的蛋白质。（译注：按热量计算）
Broccoli has more protein than beef.
大自然是有智慧的，因为它设计了一个系统，我们可以得到需要的一切，只要我们吃足够全食物来满足热量需求。
Nature was smart because it designed a system where we could get everything we need as long as we ate enough whole foods to meet our caloric needs.
例如，如果你有一天没有运动，你只能从一餐中吃掉 500 卡路里的燕麦，如果你运动，你可以吃 750 卡路里的燕麦。
For example, if you don’t exercise one day, you may only eat 500 calories of oats for a meal, and if you do exercise, you may eat 750 calories of oats for a meal.
你吃的量取决于你的热量需求，并且会受到你的大脑和饥饿信号的调节，所以你的绝对蛋白质摄入量从 16.7 克蛋白质增加到 25 克蛋白质，只需增加摄取的燕麦数量从 500 卡路里到 750 卡路里。该食物中的蛋白质百分比保持不变，这是大自然所设计的。
The amount you eat depends on your caloric needs and will be regulated by your brain and the hunger signals it sends out, so your absolute protein intake just went from 16.7 grams of protein to 25 grams of protein just by increasing the amount of oats consumed from 500 calories to 750 calories. The percentage of protein in that food remained the same, which is what nature intended.
当我们改变膳食中蛋白质的比例时，实际上改变了我们这个汽车燃料的设计和构成。
When we change the percentage of protein in our diets, we are in effect changing the design and makeup of the fuel for our car.
它在数十亿年的进化过程中更加安全和经过测试，保持燃料不变，并根据需要使用更多燃料。
It is much safer and tested over billions of years of evolution, to keep the fuel the same and just use more of it as needed.
按照汽车燃料的建议，我们应该为自己的身体做同样的事情。
We follow that advice for our car, and we should do the same for our bodies.
（ 翻译及编辑：老玉米 ）
参考文献：
Craig WJ, Mangels AR, American Dietetic Association. Position of the American Dietetic Association: vegetarian diets. J Am Diet Assoc 2009 Jul; 109(7): 1266-82.
Food & Agriculture Organization. (2001). Human Energy Requirements Report of a Joint FAO/WHO/UNU Expert Consultation. Retrieved from: Italy. http://www.fao.org/docrep/007/y5686e/y5686e08.htm#bm08.
Lappe FM. Diet for a Small Planet. New York, NY, Ballantine Books. 1985.
McDougall J. The McDougall Plan. LaVerne TN, Ingram Book Company. 1983.
Osborn TB, Mendel LB. Amino Acids in Nutrition and Growth. J Biol Chem 1914; 17: 325.
World Health Organization. (2007). Protein and Amino Acid Requirements in Human Nutrition: Report of a Joint WHO/FAO/UNU Expert Consultation. Retrieved from: http://whqlibdoc.who.int/trs/WHO_TRS_935_eng.pdf.
译后记：烧汽油的车不能烧柴油，这个是大家的共识。有智慧的大自然提供的全蔬食（whole food, plant-based）已经可以提供身体所需。
为什么还有人热衷于吃把蛋白质从食物中分离出来的蛋白质粉呢？不论是动物来源亦或是植物来源的蛋白质粉？
蛋白质粉有哪些危害？
鉴于篇幅所限，请听下回分解！
德国美女大学生 丽萨 用中文特别推荐符合 “低脂全蔬食” 原则的健康食谱公众号：
延伸阅读：吃素是技术活儿？《救命》作者Michael Greger 医生手把手教你怎么吃最有营养！
Michael Greger 医生畅销书《How Not To Die》简体中文版《救命》今年5月出版，点此了解详情。（友情链接，老玉米不参与书的销售）
关于编译者：老玉米是美国康奈尔大学坎贝尔营养研究中心《蔬食营养》证书持有者。老玉米的先生是美国内科医生(MD)，也是位“蔬食医生”(Plantrician)。
老玉米衣食无忧，退休金也准备好了，开这个公众号纯粹是吃饱了撑的。
您的点赞和转发是老玉米继续工作下去的动力！