If you know anything about cholesterol, it's probably that there's  a bad kind and a good kind.

The bad stuff clogs up your arteries  and can lead to heart attack, while the good stuff helps clear out that problem. But it's a little more complicated than that.

There's a third kind of cholesterol  that gets a lot less press. It's so off-the-radar that many  doctors don't even test for it. And 20% of people have high levels  of this mysterious third cholesterol, leading to an untold number of deaths.

So let's talk about cholesterol:  the good, the bad, and the ugly. [♪ INTRO] First, I want to say a few words in  defense of our villainized friend. Justice for cholesterol! It isn’t all bad for you.

Sometimes it just gets a bad rap. Your body makes it because it  does some pretty important stuff like helping make your cell  membranes and hormones. So we can’t just get rid of it, entirely.

But it is complicated, because there’s  more than one kind of cholesterol. In fact, there’s more than just  “good” and “bad” cholesterol. And while they got those  nicknames for legitimate reasons, they’re also not so black and white.

So let’s just start at the beginning. Cholesterol is a molecule that travels  through your blood attached to lipoproteins. These protein and fat combo molecules carry  fat to the parts of the body that need it.

Because yes, fat is also needed in moderation. So your protein and cholesterol  duos travel all over the body. But they take a few different forms.

Like Low Density Lipoprotein, or LDL  cholesterol, has more cholesterol per protein. And High Density Lipoprotein, or HDL  cholesterol, has less cholesterol per protein. And these two forms of cholesterol  can be thought of as opposing forces.

It comes down to the effects  they have on your body. See, when you have too much LDL cholesterol  floating around, it tends to stick to the walls of your blood vessels instead  of flowing through like it’s supposed to. This buildup is called plaque.

It’s not the stuff that builds up on your teeth, but it accumulates in a similar  way until there’s a big problem. As more and more plaque builds  up on the sides of your arteries, the passageway for blood gets smaller and smaller. Eventually, a plaque can block the  flow through your blood vessels.

And a clot like that can end up  giving you a stroke or heart attack. So, LDL’s nickname, “bad cholesterol,” is  probably starting to make some sense right now. But HDL cholesterol works  in a totally different way.

While too many LDLs build up in a plaque-y  plug, keeping your blood from flowing around your body, HDLs work  to clear up that problem. HDLs can remove LDLs from your bloodstream and bring them to the liver  where they’re broken down. That’s why HDL is known as “good cholesterol.” It’s had that street cred since  1977, when a famous study found that more HDL was associated  with less heart disease!

And that’s still true. Kind of. The concept of “good” cholesterol is a  bit more nuanced than “bad” cholesterol.

A 2017 study in Copenhagen found that  you really want a certain amount of HDL, around 60 milligrams per  deciliter, to benefit from it. If you have too much more than that,  your risk for heart disease goes back up. And a recent study in the US found  that if you have less than that, it’s only associated with a greater  risk of heart disease for some people.

So, overall, we can say  that LDL is bad cholesterol and HDL is good cholesterol,  with some important caveats. But when your doctor reads out your  numbers with that disapproving look, they’re often not even considering  the other kind of cholesterol. Which is bad.

And let’s just say we haven’t  found many caveats for that. I’m talking about a type of LDL called  Lipoprotein (a), or LP(a) for short. We don’t even know exactly what LP(a)s  are supposed to do in our bodies, even though they separately evolved twice over  40 million years, so they probably do something.

What we do know is that too much LP(a) can carry an even higher risk for  heart issues than regular LDL. Which is weird because LP(a)s carry less  cholesterol on average than other LDLs. It turns out that these LP(a)s  can be dangerous all on their own without the extra cholesterol  because of their size and shape.

See, they can be pretty small, so they pass  into the inner lining of your blood vessels. When too much builds up, you  can get some nasty blood clots. LP(a)s can pull off this unfortunate trick  because they look a lot like a molecule that helps break down clots in your blood vessels, but they don’t do the whole  breaking down clots thing.

So, when there are lots of LP(a) around, it gets in the way of your  body’s clot removal systems. But the most awful thing about them is the extra protein they  have called Apolipoprotein A. That ApoA protein sticks to types of  molecules that cause big-time inflammation.

So when LP(a)s get into the  walls of your blood vessels, plaque starts to build up in the inner  lining and LP(a)s destabilize the plaque. At that point, it’s more likely to come off the  artery wall and completely cut off blood flow. And that’s when heart attacks and strokes happen.

All of this kind of makes you wonder  why you’ve never heard about LP(a)s and why your doctor doesn’t check for them! I mean, c’mon! We’ve known about LP(a) since the 60s, but it’s still not on the  standard test for cholesterol?

Well, even though it’s seriously risky to  have a lot of LP(a) floating around your body, and about 20% of the world does, It just doesn’t have the same  A-list publicity as HDL and LDL. And maybe that’s because we  don’t exactly have a solution for the LP(a) problem right now. Don’t get me wrong.

We’re not completely stumped. We’re in phase III clinical  trials for RNA interference drugs that seem to significantly  reduce LP(a)s in your body. This type of treatment reversibly turns off  the gene that tells your body to make ApoA.

Basically, it adds in new genetic code that  facilitates the breakdown of the protein’s code. So you make fewer particles  of the ugly cholesterol. And if these trials keep going well, we  might have an effective treatment soon!

As for your other cholesterol problems, there are concrete steps you can  take to keep yourself healthy. As with most health related topics,  what you do to manage your levels may be different from someone else  because cholesterol can work differently depending on your genetics, your  general health, and many other factors. But pretty much every study  agrees that high LDL is bad.

So ideally, you want to try to  keep that down however you can. Eating food with high amounts  of saturated or trans fat can dangerously raise your LDL cholesterol. They seem to disrupt the process of breaking  down cholesterol and fat in your body, and they also activate the  pathway that makes cholesterol.

So avoiding fatty meats and fast food  can help get your LDL levels down. Also, exercising can increase your HDL  cholesterol, but not to dangerously high levels. So you get a lower risk for cardiovascular disease when you move your body in healthy ways.

Some people also find that medications called  statins help manage cholesterol levels. Statins slow your liver’s role in  making cholesterol in the first place, by limiting an important enzyme in the process. So, if cholesterol seems  complicated, that’s because it is.

Experts are still learning about how different  kinds of it contribute to your health, especially now that we realize it  doesn’t work the same way for everybody. But at least now you know there’s more than  just “good” cholesterol and “bad” cholesterol. Even if the third kind is pretty bad, too. [♪ OUTRO]