What is cholesterol, and what does it do?

Cholesterol — we’ve all heard the name. Most often, it crops up in relation to heart disease. 

While high levels of some forms of cholesterol are linked to heart disease risk, it might surprise some of you to learn that cholesterol is essential for your survival. 

So, we’ll focus on what it is and why you can’t live without it.

Before we start, we should mention that this article isn’t an endorsement to increase your cholesterol intake: Your body can produce all it needs.

What is cholesterol?

Cholesterol is a yellowish, waxy substance. It’s a type of lipid, or fat.

You might be most familiar with dietary cholesterol, which is present in foods such as red meat, milk, egg, and shellfish. However, the vast majority of cholesterol in your body is produced by your body.

All of your cells contain cholesterol. In fact, every cell in every animal contains it. Even plants make it, but in much smaller quantities.

Although cholesterol is produced throughout your body, liver cells create the most.

Once created, cholesterol enters your bloodstream. It travels through your blood vessels in groups called lipoproteins. 

One type is the famous high-density lipoprotein (HDL) cholesterol. This is also called "good” cholesterol. Another is the infamous low-density lipoprotein (LDL), or “bad,” cholesterol.

In simple terms, LDL mostly moves cholesterol from the liver to the rest of the body, while HDL mostly shuttles cholesterol back to the liver. 

When a compound is produced in every cell and transported far and wide in your blood, you know it’s doing something important. So, what’s it up to in there?

Membranes

Each cell is wrapped in a membrane. Among other tasks, the membrane keeps important bits inside the cell and unwanted bits outside it.

Cholesterol is a vital component of these cell membranes.

Membranes are not solid, and their parts are in constant flux. They have to be flexible enough to bend and reshape when needed but sturdy enough not to burst and leak.

Cholesterol does two seemingly opposite jobs. It helps increase the order within the membrane, keeping all the components tightly packed. But at the same time, it makes sure that the membrane stays fluid. 

Membranes also act as gatekeepers. They have channels, or pores, that are specific to different compounds. These pores allow things to enter and leave the cell as required.

Cholesterol has a job to do here, too. It interacts with protein pores, helping guide the traffic into and out of the cell.

A building block

Cholesterol’s benefits extend beyond the cell membrane. It’s also crucial in producing many compounds.

For instance, cholesterol is essential for the production of the “sunshine” vitamin, vitamin D.

A form of cholesterol called 7-dehydrocholesterol is present in the upper layers of your skin. When sunlight hits this compound, it’s converted into vitamin D.

Vitamin D is involved in a wide range of functions. For instance, it's converted into an active form called calcitriol, which controls how much calcium is absorbed from your gut into your body. 

Calcium is vital for building and maintaining bones and teeth.

So, by extension, cholesterol helps keep your bones and teeth healthy. And much more besides.

Cholesterol also forms the building blocks of steroid hormones. These include progesterone, estrogen, testosterone, cortisol, and many others.

The importance of steroid hormones can’t be overstated; they’re important players in all manner of roles, including: 

• metabolism

• inflammation

• the immune system

• the development of sexual characteristics

Bile

Bile is another bodily product with a bad name. But bile helps you digest fats and oils by making them soluble. 

And without bile, fat-soluble vitamins — such as vitamins A, D, and E — can’t be absorbed. 

Bile also helps increase the absorption of nutrients by suspending them in blobs called micelles.

And cholesterol is vital for the synthesis of bile.

Celebrating cholesterol

Although we’ve only covered a handful of cholesterol’s important functions, it’s clearly a key player in the game of life. 

Finally, we should reiterate that eating more high-cholesterol foods won’t benefit your health. Your body can synthesize all the cholesterol you need.

Also, many of the foods that contain cholesterol are high in saturated fats. It’s best to enjoy these foods once in a while.