For years cholesterol was arguably THE big bad boogeyman of the health world. It was the evil harbinger of heart attacks. It was the punchline of many a hacky sitcom joke, usually involving an admonishing wife. It was to be avoided at all costs.
As nutrition science advanced, however, it became more and more clear that, whoops, eating cholesterol actually doesn't really impact your cholesterol levels. What's more -- whoops again! -- it might not be such a great indicator of heart health at all!
This evolving view of cholesterol will come to its 180-degree conclusion at the end of this year, when the US Department of Agriculture is expected to remove cholesterol from its official shit list, with a preliminary report saying there’s “no appreciable relationship” between the cholesterol in your food and the cholesterol in your blood. Why did the medical community flip-flop, and what does it mean for your Denver omelet habit?
Cholesterol is actually necessary. And your body already makes it.
Cholesterol is a type of fat made by your liver -- it plays a role in creating vitamin D, and maintains cell membrane health. Basically, you really need cholesterol if you want to be a functioning human, and your body does a fine job producing it.
You can also find cholesterol in food, but eating high-cholesterol foods doesn’t mean your blood cholesterol levels will increase. And some people simply make more cholesterol than others. “Everyone’s body is different, and you don’t know how much cholesterol your body is going to make,” says cardiologist Dr. Nicole Weinberg.
In other words, it's possible to have naturally high cholesterol, even if you eat an extremely healthy diet… or you could have pretty low cholesterol, in spite of dining on egg yolks, burgers, and milkshakes all day.
It all started with some dead Russian rabbits
Doctors got their first up-close-and-personal look at cholesterol in the late 19th century, when they started doing autopsies on people who died of heart attacks, says historian Laurie Endicott Thomas. Often, these patients’ arteries were clogged with “a soft yellowish white material that looks and feels like cheesecake,” she says. (Sorry for ruining cheesecake for you forever.) That gunk -- atherosclerotic plaque -- contained lots of fat and cholesterol. (Like cheesecake!)
As an experiment, Russian physiologist Nikolai Anitschkow fed wild rabbits a bunch of cholesterol, and boom: They developed atherosclerosis, too.
“Anitschkow concluded that high blood cholesterol levels were a necessary cause of atherosclerosis,” Thomas says. Who wouldn’t?
Trying the low-fat strategy only made obesity worse
The logical leap from Anitschkow's findings is that eating foods with lots of cholesterol will increase the amount of cholesterol in your body. Doctors ran with this conclusion, announcing a link between dietary fats, blood cholesterol, and heart disease in the 1960s, says Dr. Roger Clemens, who was a member of the USDA 2010 Dietary Guidelines Advisory Committee. In 1984, the National Institutes of Health advised Americans to cut their dietary fat to 30% of total daily calories, kicking off the low-fat craze and convincing a legion of Spandex-clad aerobics practitioners to bring calculators to the grocery store.
The result was a rush to make everything low fat, which usually meant artificial substitutes or a bunch of sugar. Low-fat substitutes for eggs, pasta, and desserts became de rigueur, and, later, the faux-fat nightmare known as olestra was unleashed on unsuspecting consumers. Remember olestra? Maybe it’s better if you don’t.
Did avoiding cholesterol let everyone’s hearts beat as one unified, plaque-free instrument of health and happiness? Not even close. “Obesity rates increased at that time, because instead of eating good-quality fats from the earth, we ate fats made by humans, such as fake butter or foods that were processed to take the fat out,” says dietitian Julie Fortenberry. “Those are things that caused inflammation.” Remember inflammation -- it'll be important.
How could the medical community be so wrong?
Quite a few reasons, actually. First, the studies that concluded dietary cholesterol was the cause of elevated blood cholesterol levels were flawed in their design, since they often couldn't separate cholesterol from things like processed sugar and flour. Also, clinical trials among small populations don’t always translate to the total population, Clemens says, and although words like “association” and “related” (e.g., high cholesterol levels are related to heart disease) sound convincing, the actual evidence “may be quite weak.”
Meta-analyses -- when researchers analyze hundreds of studies conducted over years, and on which most current cholesterol evidence relies -- are more reliable, but they can take decades to develop, according to Clemens. Throw in some aggressive marketing by drug companies and intense lobbying by the food industry, and you have our current misinterpretation of the link between dietary and blood cholesterol.
If cholesterol doesn’t cause coronary heart disease, what does?
Heart disease isn't caused by high cholesterol levels, but by inflammation in the body, Dr. Weinberg says. Inflammation can be caused by diet, infection, and diseases -- and while it sounds like a nebulous concept, doctors can actually measure your inflammation by checking your C-reactive protein levels.
“We are pretty convinced the number-one reason for heart disease is inflammation,” adds Fortenberry. “Cholesterol is actually the good guy that comes to help put out the fire. When your body realizes there’s inflammation, it produces more cholesterol to heal the inflammation. So it’s blaming the fireman for starting the fire.”
It's not the cholesterol in the food that elevates your blood cholesterol, but certain high-cholesterol foods (like red meat) may cause inflammation, which leads to cholesterol production in the blood. Another uber-popular, but cholesterol-free, food does as well: sugar. The story of cholesterol is a classic case of mistaking correlation for causation.
The cholesterol thing burned me! How can I trust a doctor again?
The science of nutrition is always evolving, and your best bet is usually to eat unprocessed foods as much as possible, things like fruits, vegetables, whole grains, lean proteins, and healthy fats in moderate portions. Doctors don’t have all the answers, but that doesn't mean you should never take a doctor's advice.
“Weigh news about diet and health carefully,” Clemens advises. “It can take years for the strongest evidence to emerge.”
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Missy Wilkinson wonders if, 30 years from now, she’ll pen an article called "The Rise & Fall of Inflammation." Follow her on Twitter at @missy_wilkinson and Instagram at @nowlistenmissy.