是自己生产维生素D，还是服用维生素D补充剂？
编译者老玉米的家在美国芝加哥，每年冬天差不多6个月，夏天也差不多6个月，春天和秋天都是极短时间。
就说今年春天吧，4月份还下了4场雪！这是我在芝加哥十几年来，第一次4月还下雪，而且不止一场。人类活动，确实造成极端气候的现象越来越多。人类和地球哪个先完蛋？我认同视频里的观点！
终于盼来春暖花开啦。一下子就热到可以穿短袖、短裤出去散步晒太阳啦！好喜欢蒲公英花呀，尽管它经常被当作讨厌的杂草从草坪上被人除掉。
老玉米去年回国前的一天去密执根湖边晒了一天太阳，虽然不是烈阳，有层淡淡的云，但已经变成“非洲人”啦。
到了北京机场，朋友见到我的第一句话就是：你晒黑了！我知道这句话说的太客气啦，其实是差点没认出我来！
回到洛阳的家，也一直有亲朋说我黑。确实如此呀，我在满大街见到的美女一个个都是皮肤白皙的。
在美国有专门把皮肤晒黑的沙龙，这种生意在中国恐怕没有市场吧？
老玉米今天话太多啦，言归正传，趁着春暖花开，把 Michael Greger 医生最新的有关维生素D的系列视频翻译出来，总共 6集。请持续关注，不要错过噢。
维生素D补充剂对糖尿病，减肥和血压有帮助吗？（系列1）
本视频由Michael Greger医生于 2016 年 6 月 29 日发布，来自NutritionFacts.org — 能救命的营养学。
Michael Greger 医生是畅销书《How Not to Die》一书作者，中文译本：繁体版书名为《食疗圣经》。简体版书名为《救命》，将于今年5月底出版。
视频摘要： 那些维生素D水平较高的人往往患肥胖、糖尿病和高血压的比率较低，但这是因果关系吗？ 介入试验终于把维生素D做了测试。
格雷格（Greger）医生笔记
DOCTOR'S NOTE
维生素D最新视频共六集，包括：
维生素D补充剂对糖尿病，减肥和血压有帮助吗？（系列1）
Do Vitamin D Supplements Help with Diabetes, Weight Loss, & Blood Pressure?
服用维生素D补充剂会否更长寿？（系列2）
Will You Live Longer If You Take Vitamin D Supplements?
应该摄取多少维生素D？（系列3）
How Much Vitamin D Should You Take?
基于自然水平的维生素D最佳水平（系列4）
The Optimal Dose of Vitamin D Based on Natural Levels
获得维生素D的最佳途径：阳光，补充剂或沙龙？（系列5）
The Best Way to Get Vitamin D: Sun, Supplements, or Salons?
适当晒太阳的风险和好处（系列6）
The Risks and Benefits of Sensible Sun Exposure
https://v.qq.com/txp/iframe/player.html?vid=o0654h4ngm8&width=500&height=375&auto=0
上一次我深入研究维生素D是在4年前，在那之后又发表了15950篇论文。我有很多后续的工作要做。
My last in-depth video series on vitamin D was done more than four years ago — as in 15,950 papers ago. I had a lot of catching up to do.
像这样的评论文章不断出版，把维生素D吹捧成为一种名副其实的万能药。
Review articles like this continue to be published, touting vitamin D as a veritable cure-all.
维生素D受体存在于体内大部分组织，包括大脑。
The vitamin D receptor is found in most tissues in the body, including the brain.
2000个以上的基因被维生素D调节。维生素D存在的24小时内，它会让数百个基因的表现发生改变。
Upwards of 2,000 genes may be regulated by vitamin D. Within 24 hours of vitamin D exposure, you can change the expression of hundreds of genes.
将D称作维生素实际上是一种用词不当。 根据定义，维生素不能在我们的身体内合成。但是我们可以在充足的阳光下制造所需要的全部D.
The term vitamin is actually a misnomer. Vitamins, by definition, cannot be synthesized within our body. But we can make all the D we need with sufficient sun exposure.
D不是一种维生素，而是一种由皮肤通过阳光照射产生的激素。
D is not a vitamin, but a hormone, produced by our skin in response to sunlight exposure.
它不仅是一种钙调节和骨骼健康的激素，而且还是一种生育和免疫以及大脑功能的激素。
And it’s not just a hormone of calcium regulation and bone health, but a hormone of fertility and immunity and brain function.
但它是万能药，还是“假先知”？
But is it a panacea, or a false prophet?
记得维生素E曾经流行时，被吹捧为可治疗许多临床疾病。
Remember when vitamin E was the vitamin du jour, touted as curative for many clinical disorders.
“维生素E：自由基保护者”，利用公众的恐惧，通常以补充剂销售形成一个数十亿美元的生意。毕竟，血液中维生素E水平低的人患癌症的风险高出50％。
“Vitamin E: the radical protector,” with supplement sales in general forming a billion-dollar business to capitalize on the public’s fears. After all, those with low levels of vitamin E in their blood had 50% higher cancer risk.
那么维生素A或β胡萝卜素又是怎么一回事呢？
Hey, and what about vitamin A or beta carotene?
毕竟，吃大量的绿色蔬菜、红薯和其他 β 胡萝卜素丰富的食物的人患癌症的风险比较低，因此应该让人们服用β 胡萝卜素补充剂。但是，当他们被测试时，β胡萝卜素补充剂反而增加癌症发病率。（译注：从食物里获得的天然β胡萝卜素，与吃β胡萝卜素补充剂效果是不同的，食物里有成千上万种成份，这些成份有协同作用。把其中一种成份单独拿出来，就失去了协同作用。所以蔬食营养学家都主张吃“全蔬食”，而不是营养补充剂。B12是特例，是细菌生产的。）
After all, people who eat lots of greens and sweet potatoes and other beta carotene-rich foods have lower risk of cancer; so, hey, let's give people some beta carotene pills. But when they were put to the test, beta carotene pills increased cancer rates.
β胡萝卜素、维生素A和维生素E补充剂有可能会增加死亡率，实际上变成花钱买补充剂却缩短自己的寿命。
Beta carotene, vitamin A, and vitamin E supplements may increase mortality, in effect we'd be potentially paying to shorten our lifespan.
所以，你可以理解医学界对所宣称的维生素D功能的怀疑，维生素D现在正享受阳光下的时刻（译注：意为对维生素D功能公开的质疑）。
So, you can understand the skepticism in the medical community regarding claims about vitamin D, which is now enjoying its moment in the sun.
拥有价值 5 亿美元的维生素D补充剂行业并没有什么帮助，更不用说高利润的维生素D测试行业，他们喜欢谈论的是那些显示维生素D水平较高可能会降低患心脏病、癌症、糖尿病、自身免疫疾病和感染的风险的研究。
Having a half-billion dollar vitamin D supplement industry doesn’t help matters in terms of getting at the truth, not to mention the highly lucrative vitamin D-testing industry that loves to talk about the studies suggesting having higher vitamin D levels may reduce the risk of heart disease, and cancer, and diabetes, autoimmune diseases, and infections.
但大部分研究都来自观察性研究 — 这意味着研究将血液中较高的D水平与较低的疾病风险相关联。 这并不意味着维生素D是“因”（译注：因果关系中的“因”）。
But most of this research stems from observational studies — meaning studies that correlate higher D levels in the blood with lower disease risk. It doesn’t mean vitamin D is the cause.
这就像早期的β胡萝卜素数据。血液中更高的水平可能只是健康饮食的标志。
It’s like the early beta carotene data. Higher levels in the blood may have just been a marker of healthy eating.
谁拥有高β胡萝卜素水平？是那些吃了大量绿色蔬菜和红薯的人。就像维生素D水平可能只是健康行为的标志。
Who has high beta-carotene levels? Those who eat lots of greens and sweet potatoes. Just like vitamin D levels may also just be a marker for healthy behaviors.
谁拥有高D水平？ 那些是经常在外面跑来跑去的人。记住，是户外活动！户外活动！较高的维生素D水平，可能只是更多体力活动的表现，举例来说。
Who has high D levels? Those that run around outside. And those that run around outside, RUN around outside. Higher vitamin D levels may just be a sign of higher physical activity, for example.
所以，当你看到这样的研究时，在维生素D水平较高的人群中糖尿病发病率显著降低，但这并不意味着给人维生素D一定会有所帮助。必须接受测试。当这样做时，会发现维生素D补充剂没有所宣称的作用。对预防或治疗2型糖尿病没有益处。
So, when you see studies like this, showing significantly lower diabetes rates among those with higher vitamin D levels, it doesn’t mean giving people vitamin D will necessarily help. You have to put it to the test. And when you do, vitamin D supplements fall flat on their face. No benefit for preventing or treating type 2 diabetes.
因此，当补充剂公司围绕这个问题进行研究时，表明肥胖与缺乏维生素D有关系，因为大多数人群研究显示肥胖者的血液中维生素D水平较低，是因为他们的户外运动较少，又或者是因为它是脂溶性维生素，所以只是被困于所有脂肪中？
So, when supplement companies wave around studies like this, suggesting vitamin D deficiency plays a role in obesity, because most population studies show lower vitamin D levels in the blood of those who are obese, is that because they’re exercising less, or, simply because it’s a fat-soluble vitamin, and so is just lodged in all the fat?
人们可能会认为肥胖的日光浴者会产生更多的维生素D，因为他们有更多的皮肤表面积。但是同样的日光浴，肥胖者维生素D不到（正常体重者的）一半，因为它会被脂肪吸走。
One might expect obese sun bathers would make more vitamin D since they have more skin surface area. But the same exposure leads to less than half the D, because it gets socked away in the fat.
这就是为什么肥胖者可能需要的维生素D剂量是一般人的2到3倍— 虽然可能在减肥后，维生素D从脂肪中释出，并回到血液循环中。
That’s why obese persons may require two to three times the dose of vitamin D — though they may get it back when they lose weight, and release it back into the circulation.
所以，这将解释人口数据。事实上，当把维生素D做测试时，尝试将维生素D作为治疗肥胖症的方法，根本不起作用。
So, that would explain the population data. And indeed, when you put vitamin D to the test, try vitamin D as a treatment for obesity, it doesn’t work at all.
动脉健康也有类似的故事。那些维生素D水平低的人的冠状动脉血流量更糟糕，动脉粥样硬化较多，动脉功能较差。但如果真的在随机对照试验中进行了测试，结果令人失望。在降低血压方面也不起作用。
Similar story with artery health. Those with low vitamin D levels have worse coronary blood flow, more atherosclerosis, and worse artery function. But if you actually put it to the test in randomized controlled trials, the results are disappointing. Also ineffective in bringing down blood pressures.
这些都增加了越来越多的科学家对维生素D补充剂除了改善跌倒，骨折，普通感冒和全因死亡率之外的任何疾病的能力提出质疑。
So this all adds to the growing body of science casting doubt on the ability of vitamin D supplementation to improve anything beyond just falls, fractures, the common cold, and all-cause mortality.
等等! 什么？！ 维生素D补充剂可以让你活得更久？ 这很重要。 请看下回分解。
Wait! what?! Vitamin D supplements can make you live longer? That’s kind of important. I’ll explore that next.
（ 注：视频翻译及字幕制作：老玉米 ）
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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：
往期热文推荐：
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)。
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