There's nothing else in it.

沒有其他成分。

Pancake mix, on the other hand, is only about 11% fat.

反觀鬆餅粉，只有百分之 11 的脂肪。

And, yet, olive oil is good for you, and pancake mix is not.

但橄欖油卻比較健康，而鬆餅粉不健康。

Why is that?

為什麼呢？

As it turns out, the amount of fat we eat doesn't impact our weight or our cholesterol or our risk of heart disease nearly as much as what kind of fat we eat.

事實證明，我們吃下去的油脂含量並不會影響體重、膽固醇，或是得到心臟病的機率，吃下油脂的種類才會影響。

But let's back up:

讓我們看看一些背景知識：

What is fat?

什麼是脂肪？

If we were to zoom in on a salmon, which is a fatty fish,

把鮭魚放大來看，鮭魚是種很肥的魚。

past the organs, past the tissues, into the cells, we would see that the stuff we call fat is actually made up of molecules called triglycerides, and they are not all alike.

穿過器官、組織，進入細胞，我們可以看到所謂的脂肪事實上是由被稱作三酸甘油酯的分子所組成，而它們並不是都是一樣的。

Here's one example.

這有一個例子，

Those three carbons on the left, that's glycerol.

左邊這三個碳（C），那是甘油（丙三醇）。

Now, you can think of that as the backbone that holds the rest of the molecule together.

你可以把它想成一條支撐著其餘所有分子的骨幹。

The three long chains on the right are called fatty acids, and it's subtle differences in the structures of these chains that determine whether a fat is, let's say, solid or liquid.

右邊三條長鏈叫做脂肪酸，而這些長鏈中細微的不同決定了脂肪的種類，比如說，固態或液態脂肪。

Whether or not it goes rancid quickly, and most importantly, how good or how bad it is for you.

或脂肪腐敗的速度快慢，還有最重要的，是否對健康有益。

Let's take a look at some of these differences.

讓我們來看看這些差別。

One is length.

其一是長度。

Fatty acids can be short or long.

脂肪酸可以長或短。

Another, more important difference is the type of bond between the carbon atoms.

還有一個更重要的差別是碳原子相連的方式。

Some fatty acids have only single bonds.

有些脂肪酸只有單鍵。

Others have both single and double bonds.

其他的同時有單鍵和雙鍵。

Fatty acids with only single bonds are called saturated, and those with one or more double bonds are called unsaturated.

只有單鍵的脂肪酸叫飽和脂肪，而那些同時有單鍵和雙鍵的則叫做未飽和脂肪。

Now, most unsaturated fats are good for you, while saturated fats are bad for you in excess.

大多數未飽和脂肪酸對你都是有益的，而過多的飽和脂肪酸則有害健康。

For saturated fats, the story pretty much ends there, but not for unsaturated fats.

飽和脂肪酸該講得差不多都講完了，但是未飽和脂肪酸則更複雜一些。

The double bonds in these molecules have a kind of weird property; they're rigid.

這些分子中的雙鍵有種很奇怪的性質，他們很死板。

So, that means there are two ways to arrange every double bond.

所以這表示每一組雙鍵有兩種連結方式。

The first is like this, where both hydrogens are on same side and both carbons are on the same side.

第一種組合像這樣，兩個氫原子在同一邊，而兩個碳離子在同一邊。

The second way is like this.

第二種組合像這樣。

Now the hydrogens and carbons are on opposite sides of the double bond.

氫原子和碳原子分別在雙鏈的兩端。

Now, even though both of these molecules are made up of exactly the same building blocks, they are two completely different substances, and they behave completely differently inside of us.

雖然這兩組分子是由完全相同的建構組元組成，它們的內容卻大不相同，在體內起的反應也截然不同。

The configuration on the left is called CIS, which you've probably never heard of.

左邊這個配置結構叫做 CIS，你可能從來沒聽過。

The one of the right is called TRANS, and you probably have heard of trans fats before.

右邊這個叫做 TRANS，就是比較常聽到的反式脂肪。

They don't go rancid, they're more stable during deep frying, and they can change the texture of foods in ways that other fats just can't.

反式脂肪不會腐敗、在油炸過程中比較穩定，還可以改變食物的口感，這是其他油脂無法做到的。

They're also terrible for your health, by far worse than saturated fat, even though technically they're a type of unsaturated fat.

但它同時也有害健康，甚至比飽和脂肪更糟，雖然反式脂肪也算是一種未飽和脂肪。

Now, I know that seems crazy, but your body doesn't care what a molecule looks like on paper.

我知道這聽起來很瘋狂，但你的身體才不管這些分子被寫成化學式長怎樣。

All that matters is the 3-D shape where the molecule fits, where it doesn't, and what pathways it interferes with.

身體只在乎這 3D 分子能被放在哪裡、不能被放在哪裡，還有會干擾什麼路徑。

So, how do you know if a food has trans fat in it?

要怎麼知道食物裡有沒有反式脂肪？

Well, the only sure way to know is if you see the words, "partially hydrogenated" in the ingredients list.

唯一能確定的方式是看看成分表上是否寫著「部分氫化」。

Don't let nutrition labels or advertising fool you.

別被營養標示或是廣告詞愚弄。

The FDA allows manufacturers to claim that their products contain "0" grams of trans fat even if they actually have up to half a gram per serving.

FDA 允許製造商宣稱他們的產品完全不含反式脂肪，就算每一份食物內都含了 0.5 克。

But there are no hard and fast rules about how small a serving can be, and, that means, you'll have to rely on seeing those keywords, partially hydrogenated,

但關於「一份」食物份量可以多小，並沒有硬性規定，這表示你必須依靠關鍵字「部分氫化」。

because that's how trans fats are made, by partially hydrogenating unsaturated fats.

因為反式脂肪就是由部分氫化未飽和脂肪製成的。

So, let's go back to our olive oil and pancake mix from before.

讓我們回到橄欖油跟鬆餅粉的討論上。

Olive oil is 100% fat.

橄欖油是百分之百的脂肪。

Pancake mix is only 11% fat.

而鬆餅粉只有百分之 11 脂肪。

But olive oil is mostly unsaturated fat, and it has no trans fat at all.

但橄欖油大部份是未飽和脂肪，且不含任何反式脂肪。

On the other hand, more than half the fat in pancake mix is either saturated or trans fat.

反觀鬆餅粉中過半脂肪是飽和脂肪或反式脂肪。

And, so, even though olive oil has 10 times as much fat as pancake mix, it's healthy for you, whereas pancake mix is not.

所以雖然橄欖油的油脂含量是鬆餅粉的十倍，它卻是健康的，而鬆餅粉不是。

Now, I'm not trying to pick on pancake mix.

不是刻意找鬆餅粉的碴。

There are lots of foods with this type of fat profile.

很多種食物都有飽和脂肪或反式脂肪。

The point is this: It's not how much fat you eat, it's what kind of fat.

總歸來說，重要的不是攝取油脂的量，而是油脂的種類。

And what makes a particular fat healthy or unhealthy is its shape.

決定脂肪健康或不健康的關鍵是它的組成方式。