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You may have heard of alkaline water, it's the newest health trend hitting grocery shelves.
大家或许听说过碱性水，这是商店货架上的最新的热门健康趋势。
These products are essentially just water treated to have a more basic pH between 8 and 10 instead of water's usual neutral 7.
这些产品本质上来讲就是酸碱值（pH）介于8到10之间的水，一般的水为中性7.
And supposedly, they take your internal chemistry from acidic to alkaline, leaving you more hydrated and healthy.
按照此说法，这些产品能将你的体内的化学物质从酸性变成碱性，让你更水润健康。
Drinking alkaline water can even prevent bone loss and cure cancer if the health gurus are to be believed.
如果这些健康专家可靠的话，饮用碱性水甚至可以预防骨质疏松，治愈癌症。
But science doesn't back it up as any kind of miracle drink.
但是任何这种神奇的饮品都没有科学的支持。
The claim is based on an old idea often called the acid-ash hypothesis
这种说法的依据是一种旧观念—酸-灰假说
that a more acidic body leads to health problems like cancer and osteoporosis.
身体内的酸越多就会导致健康问题，如癌症和骨质疏松症。
And if an acidic body creates bad health, then making things a little more alkaline could prevent all sorts of diseases.
如果酸性身体会让人生病，那么让身体变成碱性就能预防所有疾病。
So for decades, folks have been coming up with special diets and now, beverages like alkaline water
几十年来，人类一直在提出各种特殊饮食，现在是饮料，如碱性水
that are supposed to raise your bodily pH and thereby cure cancer somehow.
这些饮料有望增加你体内的pH值从而治愈癌症。
But, there isn't one "bodily pH".
但是根本没有一个“身体pH值”。
Human blood has a pH around 7.4, for example, while muscles are a bit more acidic at a pH around 6.1.
人类血液的pH值约为7.4，而肌肉酸性更高，其pH值约为6.1.
And it's not easy to change those numbers with what you eat or drink.
想要通过吃喝改变这些数字并不容易。
For example, a study published in 2001 is often touted as showing that special diets can tweak internal pHs
例如，2001年发表的一项研究经常被吹捧为证明了特殊饮食可以扭转体内pH值
but even it didn't actually find much of an effect.
但是其并没有发现什么效果。
The researchers prepared two meal plans for 8 volunteers: an acidifying one,
这些研究人员为8名志愿者准备了两种饮食计划：一种是酸性饮食，
where the foods had higher amounts of phosphate in them and participants drank a low-pH water
他们的食物磷酸盐含量偏高并且参与者饮用的是低pH值的水，
and an alkaline one with loads of calcium and a high-pH water.
另一种是碱性饮食，含有大量的钙以及高pH值的水。
But after 4 days on the alkaline diet, while the subject's pee was noticeably less acidic
但经过4天的碱性饮食后，虽然参试者的尿液含酸量明显减少
the average blood pH only went up 0.014 units on average.
但平均血液pH值只增加了0.014单位。
That's less than the participants' daily variation, and likely within the level of error for the instrument used to detect it.
比参试者日常变化量还低，并且在检测工具允许的误差范围内。
It's actually a good thing they didn't find any big changes to blood pH based on diet.
其实他们没有在基于饮食的血液pH值中发现任何较大变化是件好事。
The range of pH where your cells work well is really narrow so big swings in either direction can damage your organs and even be fatal.
细胞运行良好的pH值范围很窄，因此不管哪一方向的大改变都会对你的器官造成损伤，甚至可能是致命的。
That's why your body has several systems in place for keeping acid-base levels balanced.
所以你的体内有几个系统保证酸碱含量的平衡。
For example, it can respond to decreasing pHs by getting rid of one of the most common acid forming molecules—carbon dioxide— by well, breathing a little more.
例如，它可以依靠多呼吸的方式摆脱最普通的酸性形成分子—二氧化碳从而对pH值的降低做出反应。
But usually, it's your kidneys that jump into action. They take whatever you have too much of in your blood and put it into your pee.
但通常是你的肾脏立即行动。它们会将血液中过多的物质以小便的形式排出。
And that's why urine pH does change based on what you eat or drink.
因此尿液pH值确实会因为你的吃喝而改变。
In that 2001 study, for example, the alkaline diet raised the subjects' urine pH by an average of 1.02 units.
例如，在那项2001年的研究中，碱性饮食将参试者尿液pH值平均增加了1.02单位。
So if you wanted to alter your blood pH by drinking an alkaline beverage, you'd have to interfere with your kidneys which, just to be clear, is a really bad idea.
所以如果你想通过饮用碱性饮料的方式改变血液pH值，那么你需要骚扰一下你的肾脏，但这是一个糟糕的想法。
And other parts of the body also regulate their local acidity,
身体的其他部分也调节它们自己的酸性，
either by making acidic or basic compounds or by throwing whatever they don't want into the blood and letting the kidneys take care of everything.
要么是通过制造酸性或基本化合物质，要么是将不想要的物质扔进血液中，再由肾脏处理一切。
That means that your urine is pretty much the only bodily fluid you can alter by chugging alkaline water—with one other exception.
这意味着你的尿液是你可以通过碱性水改变的唯一体液——也有些其他例外。
You do have some external control over the pH in your stomach at least temporarily—
你确实可以对胃部pH值有些控制权—至少暂时如此—
because you can directly neutralize some of the acid there with what you put in it.
因为你可以直接用吃进胃里的东西抵消一些酸性。
And that's why alkaline water might be effective against one particular health issue: acid reflux.
因此碱性水或许可以有效对抗一种健康问题：胃酸反流。
Acid reflux is thought to occur because acidic stomach juices activate a digestive enzyme called pepsin.
据认为，胃酸反流的发生是因为酸性胃汁刺激了一种消化酶—胃蛋白酶。
If there's too much pepsin or it sloshes up into your esophagus or other places it doesn't belong,
如果胃蛋白酶过多或是胃蛋白酶溅进了食管或是其他不该存在的地方，
it binds to tissues and causes symptoms like burping and heartburn.
那么它就会留在组织上并导致打嗝和胃灼烧的症状。
And an article published in 2012 did find that alkaline water can deactivate pepsin.
2012年发表的一篇文章确实发现碱性水可以解除胃蛋白酶。
But that was done in dishes in a lab, not in an actual human body.
但是只在实验室的餐盘中进行了试验，并未对人体进行试验。
And we already have lots of cheap, readily available meds for neutralizing stomach acids that's the whole idea behind antacids.
我们已经有很多便宜现成可用的方法中和胃酸，就是抗酸药。
When you look closer at the other purported health benefits of drinking alkaline water, the evidence just isn't there.
当你想仔细琢磨一些饮用碱性水传说中的健康益处时，证据不在那里。
Take cancer, for example. Some scientists noticed that tumorous tissues are often more acidic than healthy tissues
例如癌症。一些科学家注意到癌组织通常比健康组织酸性更高
which is likely where people got the idea that reducing acidity could cure or prevent cancer.
可能这些人就是从这里得出这种想法的，好像减少酸性就能治愈或预防癌症。
And if that were the case, you'd think that bladder cancers would be especially susceptible to alkaline diets
如果真是这样，那么你就会认为膀胱癌尤为容易受碱性饮食影响
because urine pH can actually be influenced by what you eat.
因为尿液pH值真的会受到饮食的影响。
But a study of over 27,000 men from Finland in 2005 found that a lower urine pH didn't significantly increase the risk of developing bladder cancer.
但是2005年对27000多名芬兰男性的研究发现较低的尿液pH值并没有显著增加膀胱癌风险。
Similarly, many have claimed that alkaline water can prevent or help treat osteoporosis,
很多人宣称碱性水可以预防或帮助治疗骨质疏松症也是同理，
a disease where bones become less dense and more likely to break.
这种疾病是骨头密度变得稀疏且更容易骨折。
That's because, if your kidneys slack on the job, another way your body can
这是因为，如果你的肾脏怠工，换个说法就是你的身体会
buffer too much acid is to pull calcium and bicarbonate from bone, and less calcium means less bone mass.
缓冲过多酸，就会将骨头中的钙和碳酸氢盐挤出来，钙含量少了就意味着骨量更低。
However, a study from 2010 found no association between urine pH and a subjects' bone mass density or how many bones they broke.
但2010年的一项研究发现尿液pH值和参试者骨量密度或是骨折没有关联。
And meta-analyses have failed to find any connection between excreted acids and bone health.
荟萃分析也没发现分泌出的酸和骨头健康有任何关联。
So for all the conditions drinking alkaline water might prevent, so far we haven't seen a real case for any of them.
虽然饮用碱性水或许可以预防各种疾病，但目前为止我们并没有看见任何真实案例证明这一点。
And despite the acid-ash hypothesis existing for half a century,
尽管酸-灰假说已存在半个世纪了，
there hasn't been any direct research showing that an alkaline diet or alkaline water can improve a person's health.
但没有任何直接研究表明碱性饮食或碱性水可以改善健康。
Luckily, there don't seem to be any side effects, either, so if you want to drink alkaline water because you like the taste, more power to ya.
幸运的是，碱性水似乎也没有什么副作用，所以想喝就喝。
You'll just have some slightly more expensive pee. Thanks for watching this episode of SciShow!
只不过你的尿液更贵一点而已。感谢收看本期《科学秀》！
If you liked learning what actually happens to all that alkaline water you're drinking, you might like our episode on what doctors can learn by looking at your pee.
如果你想了解碱性水是怎么回事儿，你或许会喜欢我们的视频《医生能从你的尿液中看出什么》。
