By Kayla McDonell, RD | Authority Nutrition
High blood cholesterol levels are a known risk factor for heart disease.
For decades, people have been told that the dietary cholesterol in foods raises blood cholesterol and causes heart disease.
This idea may have been a rational conclusion based on the available science 50 years ago, but better, more recent evidence doesn’t support it.
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 the human body.
Many people think of cholesterol as being harmful, but the truth is that it’s essential for your body to function.
Cholesterol contributes to the membrane structure of every single cell in your body.
Your body also needs it to make hormones and vitamin D, and perform various other important 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 certain foods, such as eggs, meat and full-fat dairy products.
Bottom Line: 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 actually referring to the structures that carry cholesterol in the bloodstream. These are called lipoproteins.
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 makes up 60–70% of total blood lipoproteins and is responsible for carrying cholesterol particles throughout your body.
It is often referred to as “bad” cholesterol because it has been linked with 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 that people who have mostly small particles are at a greater risk of developing heart disease than those with mostly large particles.
Still, the most important risk factor is not the size of LDL particles. It’s the number. This measurement is called LDL particle number, or LDL-P.
Generally speaking, the higher 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 that HDL protects against the buildup of plaque inside your arteries.
It is often referred to as “good” cholesterol because having cholesterol carried by HDL particles is associated with a decreased risk of heart disease.
Bottom Line: Lipoproteins are particles that carry cholesterol around the body. A high level of LDL lipoproteins is associated with a greater risk of heart disease, whereas higher levels of HDL lipoproteins lower 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.
When your dietary intake of cholesterol goes down, your body makes more. When you eat larger amounts of cholesterol, your body makes less.
Because of this, foods high in dietary cholesterol have very little impact on blood cholesterol levels in most people.
However, in some people, high-cholesterol foods do cause a rise in blood cholesterol. These people make up about 25% of the population and are often referred to as “hyperresponders.” This tendency is considered to be genetic.
Even though dietary cholesterol does modestly increase LDL in these individuals, 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. People who have mainly large LDL particles actually have a lower risk of heart disease.
Hyperresponders 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.
So even though hyperresponders experience raised cholesterol levels when they increase their dietary cholesterol, the ratio of LDL to HDL cholesterol in these individuals stays the same and their risk of heart disease doesn’t seem to go up.
Of course, there are always exceptions in nutrition, and it is possible that some individuals see adverse effects from eating more cholesterol-rich foods.
Bottom Line: Most people can effectively adapt to a higher intake of cholesterol. Because of this, dietary cholesterol has little effect on blood cholesterol levels.
Dietary Cholesterol and Heart Disease
Contrary to popular belief, heart disease is not only caused by cholesterol.
Many factors are involved in the disease, including inflammation, oxidative stress, high blood pressure and smoking.
While heart disease is often driven by the lipoproteins that carry cholesterol around, dietary cholesterol has little to no effect on this.
The Myths About Cholesterol Are Based on Bad Research
The original studies that found a relationship between dietary cholesterol and heart disease were flawed.
One of the original experiments discovered this link after feeding cholesterol to rabbits, which are herbivores and do not consume cholesterol by nature.
Although these results are not relevant to human disease, the study sparked an increase in clinical studies aiming to demonstrate the same relationship in people.
Unfortunately, many of the studies that followed were also poorly designed and researchers selectively excluded information in order to sway results.
Higher-Quality Research Finds no Link With Heart Disease
More recent, higher-quality studies have shown that cholesterol in the diet is not associated with an increased risk of heart disease.
A lot of research has been done on eggs specifically. Eggs are a significant source of dietary cholesterol, but several studies have shown that eating them is not associated with an elevated risk of heart disease.
What’s more, eggs may even help improve your lipoprotein profiles, which could lower your risk.
One study in particular compared the effects of whole eggs and yolk-free egg substitute on cholesterol levels.
Individuals who ate three whole eggs per day experienced a greater increase in HDL particles and a greater decrease in LDL particles than those who consumed an equivalent amount of egg substitute.
However, it is important to note that eating eggs may pose a risk to diabetics, at least in the context of a regular Western diet. Some studies show an increased risk of heart disease in diabetics who eat eggs.
Bottom Line: Dietary cholesterol has no link with the risk of heart disease. High-cholesterol foods like eggs have been shown to be safe and healthy.
Should You Avoid High-Cholesterol Foods?
For years, people have been told that high-cholesterol foods can cause heart disease.
However, the studies mentioned above have made it clear that this is not the case.
It just so happens that many foods high in cholesterol are also among the healthiest foods on the planet.
These include grass-fed beef, whole eggs, full-fat dairy products, fish oil, shellfish, sardines and liver.
These foods are incredibly nutritious, so don’t avoid them just because of their cholesterol content.
Bottom Line: Most foods that are high in cholesterol are also super healthy and nutritious. This includes whole eggs, fish oil, sardines and liver.
Ways to Lower High Blood Cholesterol
If you have high cholesterol, you can often lower it through simple lifestyle changes.
For example, losing extra weight may help reverse high cholesterol.
Several studies show that a modest weight loss of 5–10% can lower cholesterol and decrease the risk of heart disease in overweight individuals.
There are also many foods that can help lower cholesterol. These include avocados, legumes, nuts, soy foods, fruits and vegetables.
Adding these foods to your diet can help lower cholesterol and reduce the risk of heart disease.
Being physically active is also important. Studies have shown that exercise has positive effects on cholesterol levels and heart health.
Bottom Line: High cholesterol can be lowered in many cases through simple lifestyle changes. Losing extra weight, increasing physical activity and eating a healthy diet can all help lower cholesterol and improve heart health.
Take Home Message
High blood cholesterol levels are a risk factor for heart disease.
However, dietary cholesterol has little to no effect on blood cholesterol in most people.
More importantly, there is no significant link between the cholesterol you eat and your risk of heart disease.
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