What actually causes high cholesterol? - Hei Man Chan

翻译人员: Liwen Huang 校对人员: Marie Li

In 1968, the American Heart Association made an announcement

1968 年，美国心脏协会发布了一项

that would influence people’s diets for decades:

将影响人们饮食数十年的公告：

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

他们建议一周尽量不要吃超过三个鸡蛋。

Their reasoning was that the cholesterol packed into egg yolks

他们的依据是，蛋黄中富含的胆固醇

could increase cardiovascular disease risk.

会增加心血管疾病的风险。

But it turns out that the reality is more complicated.

但结果是实际情况更为复杂。

Let's delve into digestion to understand why.

让我们探究消化来明白为什么。

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

消化一餐饭时，身体会将脂肪乳化成

that can then get absorbed in your small intestine.

随后能在小肠中被吸收的脂滴。

These lipid droplets make their way to various tissues,

这些脂滴进入各种组织，

including your liver.

包括肝脏。

There, specialized cells unpack and reassemble them

在那儿，特化细胞将它们分解重组成

into lipid-protein packages, called lipoproteins,

脂质-蛋白质复合体，称为脂蛋白，

that are optimized to flow through your bloodstream.

脂蛋白被优化以流经血液。

Lipoproteins are composed of different ratios of protein and fat,

脂蛋白由不同比例的蛋白质和脂肪组成，

so their density varies.

因此它们的密度各不相同。

VLDL, or very low-density lipoprotein,

VLDL，即极低密度脂蛋白，

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

主要富含脂肪分子， 包括甘油三酯和胆固醇。

VLDL delivers lipids to your muscle and fat cells

VLDL 将脂质输送到肌肉和脂肪细胞

to be stored and used for energy.

储存和供能。

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

之后，它被转变为 LDL， 即低密度脂蛋白。

LDL is informally known as “bad cholesterol”

LDL 被通俗地称为“坏胆固醇”，

because it’s associated with cardiovascular diseases.

因为它与心血管疾病有关。

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

这是因为 LDL 更容易 积聚在血管壁上，

which can cause inflammation.

可能会引起炎症。

The inflammation attracts specialized white blood cells, called macrophages,

炎症吸引被称为巨噬细胞的特化白细胞

to remove the LDL buildup.

来清除 LDL 的积聚。

But absorbing too many lipids can compromise macrophages,

但是吸收过多的脂质会损害巨噬细胞，

causing more inflammation and triggering more macrophage recruitment.

引起更多炎症和巨噬细胞募集。

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

当细胞聚集时， 它们形成像痂一样的纤维帽，

effectively narrowing the artery.

实际上使得动脉变窄。

This can interfere with blood flow and weaken vessel walls,

这会影响血液流动并削弱血管壁，

making clots and ruptures more likely.

增加凝块和破裂的可能性。

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

另一方面，高密度脂蛋白，或 HDL

packs more protein.

含更多的蛋白质。

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

它将血液中多余的 LDL 带回肝脏

where it can be excreted.

排出体外。

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

由于 HDL 抗炎且控制 LDL，

it’s commonly called “good cholesterol.”

它通常被称为 “好胆固醇”。

Doctors order lipid panels to understand

医生开具血脂检查以了解

the concentrations of different kinds of lipoproteins

血液中各类脂蛋白的浓度

and their building blocks in your blood.

及其组成成分。

All lipoproteins are essential to your body’s functioning—

所有脂蛋白对身体机能都至关重要，

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

但如果不同的脂蛋白失去平衡， 就可能成为一个问题。

Some people are simply predisposed to having higher cholesterol.

有些人就是容易胆固醇更高。

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

例如，某些基因变体 导致 LDL 受体表现异常，

leaving more LDL circulating.

让更多 LDL 循环。

Otherwise, different lifestyle factors can influence blood lipid levels.

除此之外，不同的生活方式因素 也会影响血脂水平。

And food is one of them.

食物就是其中之一。

So, what’s the deal with eggs?

那么，鸡蛋是怎么回事呢？

Their yolks are indeed high in cholesterol,

它们的蛋黄胆固醇确实高，

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

这促使美国心脏协会于 1968 年 发布了每周三个鸡蛋的限制。

in 1968.

But while some of the cholesterol in your blood comes directly

虽然血液中的一些胆固醇直接 源自食物中的胆固醇，

from cholesterol found in food,

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

但其实身体中绝大多数胆固醇 是由摄入的不同脂肪合成的。

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

动物、棕榈和椰子产品中的 饱和脂肪和反式脂肪

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

会促使肝脏产生更多的 VLDL 和 LDL 复合体。

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

而鱼、坚果、和种子等食物中 富含的不饱和脂肪

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

具有抗炎特性， 有助于消除 LDL 的积聚。

A food’s fat composition has a greater effect

食物的脂肪成分相较于其胆固醇水平

on blood lipid concentrations than its cholesterol levels.

对血脂浓度的影响更大。

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

因此，蛋黄中的高胆固醇 其实无需太过担心。

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

蛋黄含有一些饱和脂肪，但没有过多，

and they also contain unsaturated fats.

蛋黄也含有不饱和脂肪。

Generally, an egg a day is considered nutritious.

通常，每日一个鸡蛋被认为是有营养的。

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

但这不只是吃了什么脂肪， 而是和脂肪一起吃了什么。

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

含纤维的水果、蔬菜和全谷物

通过影响脂肪在消化道中如何被吸收 来帮助降低 LDL 水平。

by affecting how fats are absorbed in the digestive tract.

Overall, getting plenty of unsaturated fats and fiber

总的来说，摄入足量的不饱和脂肪和纤维

seems to help keep LDL in check.

似乎有助于控制 LDL。

And other activities can also impact lipid levels.

其他活动也会影响血脂水平。

It's not yet totally clear why,

原因尚未完全清楚，

but resistance training and aerobic exercise

但是抗阻训练和有氧运动

can lower LDL and increase HDL.

可以降低 LDL 并提高 HDL。

This might be because they use more blood lipids for energy

这可能是因为它们用更多的血脂来供能

and boost the activity of HDL-producing enzymes.

以及提高合成 HDL 的酶的活性。

Meanwhile, smoking increases LDL buildup,

而吸烟则可能通过释放不稳定的、

perhaps by unleashing unstable free radical molecules

破坏脂质和血管壁的自由基分子

that damage lipids and vessel walls.

增加 LDL 的积聚。

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

但是，当生活方式的改变 对控制胆固醇水平没有帮助时，

as can be the case when genetics are at play,

例如有遗传因素作用时，

we luckily have some pretty effective therapies.

幸运的是，我们有一些非常有效的疗法。

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

他汀类药物是阻断 合成 LDL 所需的肝酶的药物。

Other cholesterol medications increase the production of enzymes

其他胆固醇药物增加分解甘油三酯

that break down triglycerides and promote LDL receptor activity,

及提升 LDL 受体活性的酶的产生，

helping clear it from the bloodstream.

帮助将其从血液中清除。

When it comes to cholesterol health,

谈到胆固醇健康，

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

重要的是要考虑全局， 综合饮食和其他方面，

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

这样事情才不会， 呃，乱七八糟。