在科学秀中 我们不过多讨论科学饮食
We don’t talk a lot about dietary science here on SciShow
因为 平心而论 这样科学秀就更像是早已安排好的工厂在宣传商品 而不是帮助大众形成认知
because, frankly, it can seem like a hype factory designed more to generate goods than to generate understanding.
人们想听到的是为了健康 吃什么和不吃什么
People want to hear what to eat and what not to eat in order to be healthy.
关于这个问题……有点复杂
The problem with that… is that it’s complicated.
这个问题太复杂了而不适合用作标题
It’s too complicated to fit into a headline.
摄食大量脂肪会让你不健康 但摄食大量任何食物都是如此
Eating lots of fat will make you unhealthy, but so will eating lots of anything.
研究表明 当尝试帮助人们减肥时 减少脂肪摄入量是无用的
Studies show that cutting fat intake is useless when attempting to help people lose weight
如果那些能量用其他东西来代替 而人们往往这样做
if those calories are replaced by something else, which they tend to be.
如今 脂肪在化学上是相对明确的 但它却使饮食家 尤其是那些写了几十年的新闻工作者惶恐
Now fat is relatively straightforward chemically, but it’s boggled dietary scientists and, especially, journalists writing about it for decades.
但我们所了解的基本内容并不那么复杂 所以让我们走进脂肪的核心（去了解）
But the basics of what we understand aren’t that complicated, so let’s get to the heart of fat.
脂肪是生物体用来储能的分子结构……它们是很好的储能物质
Fats are molecules that organisms use to store energy…they are very good at that
因此 它们能转化成供生物体进行生命活动所需的大量能量
and so they can be converted into lots and lots of energy for running an organism,
无论是一粒种子成长为一棵植物 还是神经元在脑内产生刺激
whether it’s a seed growing into a plant or a neuron firing in your brain.
脂肪是特别好的储能物质
Fat is super good at energy storage.
在营养学中 我们将能量称为”卡路里”——热量的衡量单位
In nutrition, we talk about energy in “calories” which is really a measure of heat.
然而 根本上来说 要了解脂肪首先要了解它的能量密度
But, basically, the first thing to know about fat is that it is energy dense.
每克脂肪的能量要比同重量的蛋白质或碳水化合物高出两倍以上
So per gram, fat has more than twice the energy of protein or carbohydrates.
像我们所吃的所有东西一样 脂肪是由化学物质构成的
Fats, like everything we eat, are made of chemicals.
那些化学物质主要是由大量的碳原子链构成
And those chemicals are primarily composed of large chains of carbon atoms.
每个碳碳链都能在体内裂解并转化成可用的能量
Each of those carbon carbon bonds can be broken by your body and converted into usable energy.
脂肪的能量密度以及高脂肪饮食的人往往不太健康
The energy density of fat combined with the fact that people who ate high fat diets tended to be less healthy
是兴起于60年代且至少某种程度上延续至今的反脂肪潮的最初原因
was the original cause of the anti-fat craze that started in the 60s and continues at least to some extent today.
但结果表明 脂肪本身对人没有坏处
But it turns out that fats are not inherently bad for you,
实际上 它们是日常饮食必不可少的一部分
indeed, they are an absolutely necessary part of the diet.
但肯定有些脂肪比其它物质更能促进健康 有些又十分危险
But there are definitely some fats that promote health more than others, and some that are downright dangerous.
你已经听说过的主要分类：
You’ve heard of the main categories:
反式 饱和 不饱和 氢化 多元不饱和 欧米加-3-……
You got your trans, saturated, unsaturated, hydrogenated, polyunsaturated, omega 3…
所有这些都是屡次谈及却未曾论述过是什么意思的化学术语
all of these words are chemistry terms that get talked about a lot without discussing what they mean, like, at all.
但这是科学秀 所以让我们进行论述吧
But this is SciShow, so let’s go there.
碳原子有四个未配对的电子 所以每个碳原子易于和另外的四个原子结合
Carbon has four unpaired electrons, so each carbon atom likes to bond to four other things.
这是甲烷：碳原子和四个氢原子结合
This is methane: carbon bonded to four hydrogens.
是的 我在使用snatoms——我非常感兴趣的Veritasium分子模型元件
And yes, I am using snatoms– Veritasium’s molecular modeling kit which I’m very excited about.
如果这个原子是在一条饱和的碳键中 那其中的两个将会成为另外的碳原子
If the carbon is in a saturated carbon chain, two of those things will be other carbons–
除非它是在链尾
unless it’s the end of the chain.
且那其中两个将会成为氢原子
And two of those things are going to be hydrogen.
如果这条碳键看上去是一连串的碳原子 每根碳键连接两个碳和两个氢
If this is what the carbon chain looks like with a bunch of carbon atoms, each bonded to two carbons and two hydrogens
那就是一个饱和的脂肪分子
that is a saturated fat
脂肪分子往往是固体且大多存在于动物身上……还有椰子
which tend to be solid and are mostly made by animals…though also coconuts.
与饱和脂肪分子相浸透的是氢原子
The thing that saturated fats are saturated with is hydrogen.
每个碳原子与两个氢原子结合 除了最后一个是与三个氢原子结合
Every carbon is bonded to two of them, except the last, which is bonded to three.
不饱和脂肪分子不饱和
And unsaturated fats are not saturated.
它们有更少的氢原子……怎么会这样呢
They have fewer hydrogens…how?
在整条链中 它们在两个碳原子之间至少得到一个双链
Well they’ve got at least one double bond between two carbons in the chain.
每个双链意味着少两个氢原子
Each double bond means two fewer hydrogens.
所以不饱和脂肪分子没有每个碳原子拥有的氢原子多
So unsaturated fats don’t have as many hydrogens as they could have per carbon atom.
然而这并不是听上去那么小的一个改变
And this is not as minor a change as it might sound.
单链可以轻易地绕轴转动 但双链将结构固定于特定的位置
Single bonds can rotate around their axis no problem, but double bonds lock a structure into place.
双链可以将链固定成一个结或是直线
And that double bond can either lock the chain into a kink or lock it straight.
事实上 脂肪链中的双链几乎都是将链固定成一个结
In nature, a double bond in a fat chain almost always locks it into a kink.
而这防止了脂肪分子堆积成块 使得它们在室温下更能保持液态
This prevents the fat molecules from stacking into lattices making them more likely to be liquid at room temperature.
因此 不饱和脂肪往往是液态 也就是油 它们大多取自于植物和鱼类
So unsaturated fats tend to be liquid, making them oils, and come mostly from plants and fish.
结状排列称为”顺式异构体” 线状排列称为”反式异构体”
The kinked configuration is called the “cis isomer” and the straight one is the trans isomer.
“异构体” 这个词仅表示这些分子具有相同的化学分子式
The word ‘isomer’ just means that the molecules have the same chemical formula,
但是是不同的形状
but are different shapes.
这些不同的形状……很重要
And the different shapes matter…a lot.
饱和脂肪不如不饱和脂肪健康 因为饱和脂肪易于堆积
Saturated fats are less healthy than unsaturated fats because they pack together easily and
会在动脉血管中形成斑块 还会和胆固醇相互作用使之滞留血流中
can form plaques in your arteries and can also interact with cholesterol making it build up in your bloodstream.
顺式不饱和脂肪（接下来都称不饱和脂肪）不易堆积
Cis unsaturated fats (which the rest of the world just calls unsaturated fats) don’t stack well
因此不会形成斑块
and so don’t form plaques.
因此差异就存在了 但差异并不像我们过去认为的那样大
So that difference exists, but it isn’t as big as we used to think it was.
结果表明我们的身体很善于处理我们摄取的任何东西……
It turns out our bodies are pretty good at dealing with whatever we throw at it…
只要我们的身体足够熟悉（这些物质）
as long as it’s fairly familiar.
迄今为止 更糟糕的是反式不饱和脂肪
Worse by far are the trans unsaturated fats.
这些几乎都是通过增加氢原子或”部分氢化”了一些不饱和脂肪（如大豆油）制造的
These are almost all manufactured by adding hydrogens or “partially hydrogenating” some unsaturated fat like soybean oil.
所以反式脂肪和氢化脂肪是同样的东西……
So trans fat and hydrogenated fats are the same thing…
一个指的是它们产生的过程 另一个指的是它们的化学结构
one refers to the process through which they are created, the other their chemical structure.
这些脂肪均有双链且易于堆积……事实上 它们比饱和脂肪更易于堆积
These are fats that have double bonds AND stack well…in fact, they stack even better than saturated fats
而我们的生物化学系统并不是专为分解它们而设计的
AND our biochemical systems aren’t designed to break them down
而且它们与胆固醇不能相互作用
AND they interact badly with cholesterol.
日常反式脂肪的摄入增加2％就相当于增加了23％的心脏病几率
A two percent increase in daily intake of trans fat corresponds with a 23% increase in the chance of heart disease.
令人惊奇地是 它们最初被视为饱和脂肪的健康替代品
Amazingly they were initially seen as a healthy alternative to saturated fats
然而如今在美国 它们正被全面取缔
and are now in the process of being completely banned in America.
如今 即使在这些种类中有变种 在那变种中有
Now, even in these categories there’s variation, and inside that variation comes
更多活跃却不为人知的研究领域
more active areas of research where less is known for sure.
多元不饱和脂肪或有超过一个双链的脂肪或多或少比单不饱和脂肪健康……
Polyunsaturated fats, or fats with more than one double bond might be more or less healthy than monounsaturated fats…
因为它们既有利又有弊 所以没有人真正赞成
no one really agrees because they both have benefits and drawbacks,
而且它对整条链中双链的位置起着重要作用
and it matters where in the chain the double bonds are.
你大概可能二者兼有之
You should probably have some of both.
如果双链恰好在倒数第三个碳原子前面
And If the double bond is just before the third carbon from the end,
我们称之为欧米加-3-脂肪酸 它们似乎有很多益处
we call that an omega three fatty acid and they seem to have a wide range of benefits.
它们也是两种基本脂肪酸之一（另一种是欧米加-6-）
And they’re also one of the two essential fatty acids (the other being omega 6).
基本化合物是那些我们身体赖以正常运转但自身不能合成的化学成分……
Essential compounds are chemicals that our bodies need to function correctly but can’t manufacture on their own…
因此 为了生存 我们确实需要摄食那些脂肪
so we literally need to eat those kinds of fats in order to survive.
的确 一般而言 我们摄取脂肪是为了生存
And indeed, we need to eat fat in general to survive.
适量的脂肪对身体有好处
It’s good for you…in the correct quantities.
那些就是关于脂肪的基本知识
So those are the basics of fat you guys!
脂肪本身贮存了大量的能量 因此当你需能时 它们是很好的选择
They have TONS of energy in them, so they’re great when you need calories.
但也易于摄食过多卡路里
But they also make it super easy to eat too many calories.
它们对生命是必不可少的 尝起来也不错 对身体也好
They’re absolutely necessary for life, they taste good and are good for you,
但不饱和脂肪更好 而反式脂肪很可能害死你
but unsaturated fats are better and trans fats might very well kill you.
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If you want to help support this show, just go to patreon.com/scishow.
如果你对Snatoms感兴趣——我不确定这个募资敲门砖是否还在运行——
And if you’re interested in Snatoms– I’m not sure if the kickstarter is still going on–
但它们基本上就是这些小型磁模元件
but they’re basically these little magnetic modeling kits.
它们真酷 我们会在简介里附上链接
They’re very cool, we’ll put a link in the description.