The Truth About How Your Diet Affects Your Cholesterol

High cholesterol is a serious problem in America, affecting nearly one in three adults. It may seem that simply avoiding high-cholesterol foods is a good way to solve this public health crisis — but in reality, the connection between diet and blood cholesterol levels is much more complicated.

Yes, dietary cholesterol is present in certain foods, and eating these can, in fact, affect blood cholesterol levels in the body. But even the leading health and nutrition experts aren't sure exactly how big a role cholesterol from food plays in a person's overall cardiovascular health.

Because cholesterol is also produced by our bodies, genetics are also a big factor. Other lifestyle components — like physical activity, smoking and eating a lot of processed or fried foods (whether they're high in cholesterol or not) — can make a difference, too.

It's a complex topic, and it's normal to be confused about what you should — and shouldn't — eat and do to keep your cholesterol at a healthy level. Here, we'll break down the latest science on the topic, and get expert opinions on what really matters.

Cholesterol is a fatty, waxy substance that circulates in our blood, explains Luke Laffin, MD, a cardiologist at the Cleveland Clinic. It's produced by the liver and, because of genetic and lifestyle differences, some people make more cholesterol than others.

The body needs cholesterol to build cells, according to the American Heart Association. But too much cholesterol can build up and form plaques that clog arteries, making them stiff and narrow, so it's difficult for blood to circulate freely in the body. This condition is called atherosclerosis, and it raises a person's risk for blood clots, heart attacks and strokes.

Read more: The 9 Best Cholesterol-Lowering Foods

There are two types of cholesterol: LDL, which stands for low-density lipoprotein, and HDL, which stands for high-density lipoprotein. LDL cholesterol is considered "bad" cholesterol, because it increases the risk of plaque buildup.

HDL cholesterol, on the other hand, is considered "good" cholesterol because it transports cholesterol molecules from the bloodstream back to the liver for disposal, according to the Harvard T.H. Chan School of Public Health.

Just like cholesterol is produced in the human body, it's also produced by the animals we consume for food. "Anything with a liver is going to have cholesterol," says Gabrielle Mancella, RD, a corporate wellness dietitian at Orlando Health.

That cholesterol isn't just circulating in animals' bloodstreams; it's also present throughout their bodies — and in the animal products we eat, such as meat, poultry, eggs, milk and other dairy products.

Read more: 4 Reasons to Eat Just a Little Bit Less Meat

Plants, on the other hand, do not contain cholesterol. Some plant-based products (like coconut and palm oil), however, do contain fats that can affect cholesterol levels in the body — more on that later.

"One of fiber's most important jobs is to remove cholesterol from the body. It basically creates a little nest for the cholesterol molecules to sleep in and be shipped out with our waste."

Scientists used to think that eating a lot of dietary cholesterol would obviously have a big impact on cholesterol levels in the blood. High-cholesterol foods that had previously been though of as healthy — like eggs and shrimp, for example — have gotten a bad rap because of these assumptions.

Today, health experts know it's not that simple. In a June 2018 review published in the journal Nutrients, researchers concluded that the latest science "does not support the notion that dietary cholesterol increases the risk of heart disease in healthy individuals."

Instead, research suggests that trans and saturated fats found in foods have a much bigger effect on cholesterol levels than dietary cholesterol itself. In fact, the review states, there is "ample evidence that saturated fatty acids and trans-fats increase cardiovascular disease risk." One reason for the confusion could be that foods high in cholesterol — like butter, cheese and beef, for example — also tend to be high in saturated fats.

Read more: Your Ultimate Guide to Fats and Why Your Body Needs Them

So does that mean dietary cholesterol plays no role whatsoever in blood cholesterol? Not exactly, says Dr. Laffin. "There still is not true consensus from medical professionals on this topic," he says.

"We know that about 70 to 80 parent of cholesterol is produced in the liver, and we really don't have a lot of control over that," he adds. "But the other 20 to 30 percent can certainly be related to diet, and that can really vary from person to person."

For example, the 2018 review points out that it's still unclear how dietary cholesterol affects people with diabetes. Some people also have genetic predispositions that make them more sensitive to the effects of dietary cholesterol, says Dr. Laffin.

For overall heart health and healthy cholesterol levels, Dr. Laffin recommends following a "diet of moderation," and favors a Mediterranean-style eating plan.

"Eating more whole foods and more plant-based foods, and eliminating packaged and highly processed foods, are some of the best things you can do," he says.

Mancella agrees that it's important to limit the amount of saturated fats in your diet, and to make sure you're getting plenty of plant-based foods like fruits, vegetables, nuts and seeds.

Not only are these foods low in saturated fat and free of dietary cholesterol, but they're also high in fiber — an important weapon in the fight against high blood cholesterol.

"One of fiber's most important jobs is to remove cholesterol from the body," says Mancella. "It basically creates a little nest for the cholesterol molecules to sleep in and be shipped out with our waste."

Read more: 19 High-Fiber Foods — Some May Surprise You!

It's also important to avoid trans fats, which are often found in fried foods, packaged baked goods, margarines and vegetable shortening. Like saturated fats, these molecules trigger the liver to make more cholesterol and have been shown to raise levels of LDL cholesterol specifically.

What's more, a July 2020 analysis in BMJ Evidence-Based Medicine reviewed current diet guidelines for people with familial hypercholesterolemia and concluded that a low-carbohydrate diet significantly improves cardiovascular disease biomarkers compared to a low-fat diet, calling for more clinical trials around this.

And while Dr. Laffin doesn't think people should cut out shellfish completely, he does warn that this food group tends to be high in cholesterol. A 3-ounce serving of shrimp, for example, is only about 100 calories but contains 179 milligrams of cholesterol, according to the USDA; that's 60 percent of the recommended daily value of 300 milligrams.

"The bottom line is we really don't know what that means for every person," he says. "When we talk about how people should eat more fish, we really don't mean shrimp and lobster and crab — we mean things like salmon and halibut."

As for eggs, the jury is still out on their true impact on cholesterol levels in the body.

While the 2018 review found no good evidence that eating eggs impacted cardiovascular health, a more recent study did find cause for concern: A March 2019 meta-analysis published in JAMA found that the more eggs people ate, the higher their risk for cardiovascular disease and death — a relationship that seemed to be directly linked to dietary cholesterol intake.

Still, says Dr. Laffin, eggs are a good source of protein and nutrients like vitamin B12 and zinc, and most people can eat up to six eggs a week without worrying about their effects on heart health. (One large egg contains 186 milligrams of cholesterol, or about 62 percent of the recommended daily value, according to the USDA.)

While diet is certainly important for overall cardiovascular health, sometimes even the healthiest diet and lifestyle may not be enough to fully protect against high cholesterol. This may be especially true for people with a genetic condition called familial hypercholesterolemia, notes the American Heart Association.

"We've seen people who are vegetarians and marathon runners who still have dangerously high levels," says Dr. Laffin. "If you have family members with really high cholesterol or a high risk for heart disease — if they've had a heart attack in their 30s or 40s, for example — that can be a sign that there's a genetic component there."

That's why it's important to know your cholesterol numbers, as well as your family history, and to talk with your doctor if you think you're at risk for or have high cholesterol.

"It's not that it's one or the other, lifestyle or medication," says Dr. Laffin. "You still have to watch your diet and exercise and those things are going to be beneficial — but it may be just as important to add a drug to your regimen as well."