What actually causes high cholesterol? - Hei Man Chan

譯者: Lilian Chiu 審譯者: 麗玲 辛

In 1968, the American Heart Association made an announcement

1968 年，美國心臟協會 發佈了一項公告，

that would influence people’s diets for decades:

在往後的數十年影響了人類的飲食：

they recommended that people avoid eating more than three eggs a week.

他們建議大家一週 不要吃超過三顆蛋。

Their reasoning was that the cholesterol packed into egg yolks

他們的論據是，蛋黃中富含膽固醇，

could increase cardiovascular disease risk.

可能會增加心血管疾病的風險。

But it turns out that the reality is more complicated.

但事實證明，實情更複雜。

Let's delve into digestion to understand why.

為了了解原因，咱們先來 深入探討消化過程，

As your body processes a meal, it emulsifies fats into lipid droplets

當你的身體在處理一頓餐點時， 它會將脂肪乳化成脂肪滴，

that can then get absorbed in your small intestine.

脂肪滴在小腸中會被吸收掉。

These lipid droplets make their way to various tissues,

這些脂肪滴會進入多種組織中，

including your liver.

包括肝臟。

There, specialized cells unpack and reassemble them

肝臟裡有特化細胞 會將它們拆解再重新組裝

into lipid-protein packages, called lipoproteins,

成為脂肪與蛋白質的 複合物，稱為脂蛋白，

that are optimized to flow through your bloodstream.

被優化的脂蛋白能夠隨血液流動。

Lipoproteins are composed of different ratios of protein and fat,

脂蛋白是由不同比例的 蛋白質和脂肪組成，

so their density varies.

因此它們的密度也不盡相同。

VLDL, or very low-density lipoprotein,

極低密度脂蛋白（VLDL）

is mostly packed with fatty molecules, including triglycerides and cholesterol.

主要成分為脂肪分子，

包括三酸甘油酯和膽固醇。

VLDL delivers lipids to your muscle and fat cells

VLDL 會將脂質遞送 給肌肉和脂肪細胞，

to be stored and used for energy.

存儲起來並當能量來使用。

Afterwards, it’s converted into LDL, or low-density lipoprotein.

之後，它會被轉換為 低密度脂蛋白（LDL），

LDL is informally known as “bad cholesterol”

LDL 有個非正式的稱號： 「不好的膽固醇」，

because it’s associated with cardiovascular diseases.

因為它與心血管疾病相關。

This is because LDL is more prone to accumulating on blood vessel walls,

原因是因為 LDL 較容易 堆積在血管壁上，

which can cause inflammation.

就可能導致炎症。

The inflammation attracts specialized white blood cells, called macrophages,

炎症會吸引特化白血球細胞，

叫做巨噬細胞，

to remove the LDL buildup.

以除去堆積的 LDL。

But absorbing too many lipids can compromise macrophages,

但吸收過多的脂質 可能會危害到巨噬細胞，

causing more inflammation and triggering more macrophage recruitment.

造成炎症加劇， 因而需要更多巨噬細胞。

As the cells clump together, they form a fibrous, scab-like cap,

當這些細胞聚集在一起， 會形成像痂一樣的纖維狀覆蓋物，

effectively narrowing the artery.

實際上讓動脈變狹窄。

This can interfere with blood flow and weaken vessel walls,

這可能會干擾血流、 使血管壁變脆弱，

making clots and ruptures more likely.

增加血塊形成和血管破裂的可能性。

High-density lipoprotein. or HDL, on the other hand,

另一方面，高密度脂蛋白（HDL）

packs more protein.

由更多蛋白質組成。

It picks up excess LDL in the blood and brings it back to the liver,

它會把血液中多餘的 LDL 帶回肝臟，

where it can be excreted.

從那裡排出。

Because HDL is anti-inflammatory and keeps LDL in check,

由於 HDL 可以對抗炎症，

也能控制 LDL 的量，

it’s commonly called “good cholesterol.”

因此通常被稱為「好的膽固醇」。

Doctors order lipid panels to understand

醫生會透過血脂檢查

the concentrations of different kinds of lipoproteins

來了解各種脂蛋白 及其構成成份的濃度。

and their building blocks in your blood.

All lipoproteins are essential to your body’s functioning—

身體要運作，每種脂蛋白 都是不可或缺的——

but it can become a problem if the different kinds get out of balance.

但如果不同種類的脂蛋白 失去平衡，就可能造成問題。

Some people are simply predisposed to having higher cholesterol.

有些人天生就比較容易 有較高的膽固醇。

For example, certain gene variants cause LDL receptors to behave abnormally,

比如，某些基因變異會導致 LDL 受體的運作異常，

leaving more LDL circulating.

讓更多 LDL 在體內循環。

Otherwise, different lifestyle factors can influence blood lipid levels.

此外，某些生活方式 也可能會影響血脂濃度。

And food is one of them.

其中之一是食物。

So, what’s the deal with eggs?

那麼，這和蛋有什麼關係？

Their yolks are indeed high in cholesterol,

蛋黃的膽固醇含量的確很高，

which prompted the American Heart Association’s three egg weekly limit

因此美國心臟協會在 1968 年 提出每週三顆蛋的上限。

in 1968.

But while some of the cholesterol in your blood comes directly

但，雖然血液中的膽固醇 部分直接來自食物中的膽固醇，

from cholesterol found in food,

your body actually makes a vast majority of it from the different fats you consume.

其實大部分是由身體 用攝取的各種脂肪製造出來的。

Saturated and trans fats, found in animal, palm, and coconut products

肉類、棕櫚油，和椰子產品中的 飽和脂肪和反式脂肪

can drive your liver to create more VLDL and LDL packages.

會促使肝臟產生更多 VLDL 和 LDL 複合物。

Unsaturated fats, meanwhile, are abundant in foods like fish, nuts, and seeds,

相對的，在魚、堅果，和種子 等食物中富含的不飽和脂肪

and have anti-inflammatory properties that help counteract LDL buildup.

則具有抗炎特性， 有助於消除 LDL 的堆積。

A food’s fat composition has a greater effect

食物的脂肪組成

比它的膽固醇含量 更會影響血脂濃度。

on blood lipid concentrations than its cholesterol levels.

So the high cholesterol found in egg yolks isn’t actually of too much concern.

所以其實可以不用太擔心 蛋黃中的高膽固醇。

Egg yolks contain some saturated fat, but not too much—

蛋黃含有一些飽和脂肪，但不太多，

and they also contain unsaturated fats.

且蛋黃也含有不飽和脂肪。

Generally, an egg a day is considered nutritious.

一般來說，一天 吃一個蛋是很營養的。

But it's not just what fats you eat, but what you eat them with.

但，重點不只是你吃進什麼脂肪，

還有你搭配什麼一起吃。

Fibrous fruits, vegetables, and whole grains help lower LDL levels

多纖維的水果、蔬菜，和全穀類 都有助於降低 LDL 含量，

by affecting how fats are absorbed in the digestive tract.

因為它們可以影響 消化道中的脂肪吸收方式。

Overall, getting plenty of unsaturated fats and fiber

總的來說，攝取 大量不飽和脂肪及纖維

seems to help keep LDL in check.

似乎有助於控制 LDL。

And other activities can also impact lipid levels.

其他活動也可能會影響脂質含量。

It's not yet totally clear why,

目前還無法確定為什麼，

but resistance training and aerobic exercise

但阻力訓練和有氧運動

can lower LDL and increase HDL.

可以降低 LDL 並增加 HDL。

This might be because they use more blood lipids for energy

原因可能是因為這些活動 會使用較多的血脂作為能量，

and boost the activity of HDL-producing enzymes.

並提升 HDL 生成酵素的活性。

Meanwhile, smoking increases LDL buildup,

同時，吸煙會增加 LDL 的堆積，

perhaps by unleashing unstable free radical molecules

可能是因為會釋放 不穩定的自由基分子，

that damage lipids and vessel walls.

傷害脂質和血管壁。

But when lifestyle changes don’t help to manage cholesterol levels,

但，若改變生活方式仍無法 協助控制膽固醇含量時，

as can be the case when genetics are at play,

比如若是遺傳上的問題 就有可能如此，

we luckily have some pretty effective therapies.

很幸運，我們還是 有一些非常有效的療法。

Statins are drugs that block a liver enzyme required to produce LDL.

他汀類藥物可以阻斷 製造 LDL 必要的肝臟酵素。

Other cholesterol medications increase the production of enzymes

其他降膽固醇藥物 可以增加酵素的生成，

that break down triglycerides and promote LDL receptor activity,

這些酵素會分解三酸甘油酯， 並促進 LDL 受體的活性，

helping clear it from the bloodstream.

有助於清除血液中的 LDL。

When it comes to cholesterol health,

說到膽固醇健康，

it’s important to keep the whole picture in mind— on and off the plate—

重要的是要考量整體情況——

包括盤上的食物和其他因子——

so things don't get all, you know, scrambled.

才不會搞到像炒蛋一樣亂糟糟。