By Aparna Mani, MD, PhD
MGH Medical Walk-In Unit

We hear about cholesterol almost as often as we hear about the weather on the news these days – but what is it really and why is it such a hot topic?  Cholesterol is actually a type of fat particle that travels around in the bloodstream. It’s true that we get cholesterol from food, but our body also makes its own cholesterol in the liver. In fact, the liver can produce all the cholesterol our body needs even if we do not take in any cholesterol from our diet.  Foods that are high in cholesterol include mostly animal sources like meats, eggs, fish, poultry, and dairy products like whole milk and butter. Plant-based foods like fruits, vegetables, tofu and grains contain little to no cholesterol.

So what do we need cholesterol for?  Well, cholesterol is used for a couple of different things.  It’s a component of the outer layer of all of the cells in our body, it helps to make vitamin D and hormones like estrogen and testosterone, and it helps in the digestion of fats in the intestine. 

What’s the story about the good versus bad cholesterol?  To understand this a bit better, we need to take a closer look at how cholesterol gets around the body.  Because cholesterol does not mix easily with blood, it’s carried around in the bloodstream by a particle that acts as a kind of vehicle called a lipoprotein. There are several types of lipoproteins, but the ones you have probably heard of are HDL and LDL.  The LDL particles carry cholesterol around and deliver it wherever it’s needed in our body.  However, if we have too much LDL, the excess cholesterol can be deposited on the walls of our blood vessels.

Why is this a bad thing?  The deposits of cholesterol in the coronary arteries, the blood vessels that supply our heart, can form plaque. It’s exactly this plaque that can eventually rupture and cause a blockage in a coronary artery, leading to a heart attack. This is why LDL is often referred to as ’bad’ cholesterol.  But let’s look at another particle:  HDL cholesterol. What makes HDL different is that instead of depositing cholesterol in various parts of our body (including blood vessels), it picks up any extra cholesterol that is lying around and brings it back to the liver. The liver can take this extra cholesterol and either make it into something useful or recycle it.  This is why HDL is referred to as ‘good’ cholesterol.

The balance between LDL and HDL in our body is important.  We want to keep the levels of LDL low and the levels of HDL high so  our body can function well without creating too much cholesterol or plaque build-up in our blood vessels. Some of us might have a genetic predisposition that determines our LDL and HDL levels, but we also have a role in striking this balance through diet and lifestyle.  By eating a diet rich in fruits, vegetables and grains we can keep our LDL low.  Healthy activities such as exercise and refraining from smoking also help to strike the right balance between HDL and LDL cholesterol. Some of us may need medications to modify our cholesterol levels in addition to following healthy habits.  According to the American Heart Association, adults should get their cholesterol levels checked periodically so  their health care provider can make recommendations for keeping their cholesterol levels in good balance.