For decades, people have been told that the dietary cholesterol in foods raises blood cholesterol levels and causes heart disease. This idea may have been a rational conclusion based on the available science 50 years ago, but more recent evidence calls this into question.
High blood cholesterol levels are a known risk factor for heart disease. Whether dietary cholesterol causes them is a different question.
This article takes a close look at the current research on dietary cholesterol and the role it plays in blood cholesterol levels and heart disease.
What is cholesterol?
Cholesterol is a waxy, fat-like substance that occurs naturally in your body.
Many people think that cholesterol is harmful, but the truth is that it’s essential for your body to function.
Cholesterol contributes to the membrane structure of every cell in your body.
Your body also needs it to make hormones and vitamin D, as well as perform various other essential functions. Simply put, you could not survive without it.
Your body makes all the cholesterol it needs, but it also absorbs a relatively small amount of cholesterol from some foods, such as eggs, meat, and full-fat dairy products.
SUMMARY
Cholesterol is a waxy, fat-like substance that humans need to survive. Your body makes cholesterol and absorbs it from the foods you eat.
Cholesterol and lipoproteins
When people talk about cholesterol in relation to heart health, they usually aren’t talking about cholesterol itself.
They are referring to lipoproteins — the structures that carry cholesterol in the bloodstream.
Lipoproteins are made of fat (lipid) on the inside and protein on the outside.
There are several kinds of lipoproteins, but the two most relevant to heart health are low-density lipoprotein (LDL) and high-density lipoprotein (HDL).
Low-density lipoprotein (LDL)
LDL comprises 60–70% of total blood lipoproteins and is responsible for carrying cholesterol particles throughout your body.
It’s often referred to as “bad” cholesterol, as it has been linked to atherosclerosis, or the buildup of plaque in arteries.
Having a lot of cholesterol carried by LDL lipoproteins is associated with an increased risk of heart disease. In fact, the higher the level, the greater the risk.
There are different types of LDL, mainly broken down by size. They are often classified as either small, dense LDL or large LDL.
Studies show Trusted Source that people who have mostly small particles are at a greater risk of developing heart disease than those with mostly large particles.
Still, the size of LDL particles is not the most important risk factor — it’s the number of them. This measurement is called LDL particle number, or LDL-P.
Generally, the higher the number of LDL particles you have, the greater your risk of developing heart disease.
High-density lipoprotein (HDL)
HDL picks up excess cholesterol throughout your body and takes it back to your liver, where it can be used or excreted.
Some evidence indicates Trusted Source that HDL protects against the build up of plaque inside your arteries.
It’s often referred to as “good” cholesterol, as having cholesterol carried by HDL particles is associated with a decreased risk of heart disease.
Lipoproteins are particles that carry cholesterol around your body. A high level of LDL lipoproteins is associated with a greater risk of heart disease, whereas a high level of HDL lipoproteins lowers your risk.
How does dietary cholesterol affect blood cholesterol?
The amount of cholesterol in your diet and the amount of cholesterol in your blood are very different things.
Although it may seem logical that eating cholesterol would raise blood cholesterol levels, it usually doesn’t work that way. The body tightly regulates the amount of cholesterol in the blood by controlling its production of cholesterol.
Blood cholesterol levels are mostly determined by the amount of fats and carbohydrates in the diet, not by dietary cholesterol. Recent research has found that for most people, consuming an egg a day had no affect on their cholesterol.
However, in some people, high-cholesterol foods raise blood cholesterol levels. These people are often referred to as “hyperresponders.” This tendency is considered to be genetic.
Even though dietary cholesterol modestly increases LDL Trusted Source in these people, it does not seem to increase their risk of heart disease.
This is because the general increase in LDL particles typically reflects an increase in large LDL particles — not small, dense LDL. In fact, large LDL particles appear not toTrusted Source have any effect on a person’s risk of heart disease.
An older study Trusted Source found that hyper responders also experience an increase in HDL particles, which offsets the increase in LDL by transporting excess cholesterol back to the liver for elimination from the body.
As such, while hyper responders experience raised cholesterol levels when they increase their dietary cholesterol, the ratio of LDL to HDL cholesterol in these people stays the same, and their risk of heart disease doesn’t seem to go up.
Of course, there are always exceptions in nutrition, and some individuals may see adverse effects from eating more cholesterol-rich foods.
Medically reviewed by Avi Varma, MD, MPH, AAHIVS, FAAFP