A low-carb, high-fat “ketogenic” diet may be linked to higher levels of “bad” cholesterol and double the risk of cardiovascular events like blocked arteries, heart attacks and strokes, according to new research.
“Our study found that regular consumption of a self-reported low-carbohydrate, high-fat diet was associated with higher levels of LDL cholesterol, or ‘bad’ cholesterol, and increased risk of heart disease,” said the study’s lead author, Dr. Iulia. Iatan, of the Heart Healthy Program Prevention Clinic, St. Paul Hospital and Center for Cardiopulmonary Innovation at the University of British Columbia in Vancouver, Canada, in a news release.
In the study, researchers defined a low-carb, high-fat (LCHF) diet as 45% of total daily calories from fat and 25% from carbohydrates. The study was presented Sunday at the American College of Cardiology Annual Scientific Session in conjunction with the World Congress of Cardiology.
“The rationale for our study came from the fact that we would see patients in our cardiovascular prevention clinic with severe hypercholesterolemia following this diet,” Iatan said during a presentation at the session.
Hypercholesterolemia, or high cholesterol, increases a person’s risk of having a heart attack or other adverse cardiovascular events.
“This led us to wonder about the relationship between these low-carbohydrate, high-fat diets, lipid levels, and cardiovascular disease. And so despite this, there is limited data on this relationship,” he said.
The researchers compared the diets of 305 people eating a low-carb diet with about 1,200 people eating a standard diet, using health information from the UK Biobank database, which followed people for at least a decade. .
Researchers found that people on the LCHF diet had higher levels of low-density lipoproteins, also known as LDL, cholesterol, and apolipoprotein B. Apolipoprotein B is a protein that coats LDL cholesterol proteins and may better predict heart disease that elevated levels of LDL cholesterol can.
The researchers also noted that the total fat intake of the LCHF diet participants was higher in saturated fat and had twice the intake from animal sources (33%) compared to those in the control group (16%).
“After an average of 11.8 years of follow-up, and after adjusting for other risk factors for heart disease, such as diabetes, high blood pressure, obesity, and smoking, people on a low-carb diet had twice the risk increased risk of having several major cardiovascular events, such as blocked arteries that needed to be opened by stenting procedures, heart attack, stroke, and peripheral arterial disease,” the researchers found, according to the news release.
The researchers said in the statement that their study “can only show an association between diet and increased risk of major cardiac events, not a causal relationship,” because it was an observational study, but their findings warrant further study, “especially when approximately 1 in 5 Americans report being on a low-carb, ketogenic, or full ketogenic diet.”
Iatan said the study’s limitations included measurement errors that occur when dietary assessments are self-reported, the study’s small sample size, and that most participants were British and did not include other ethnic groups.
The study also looked at the longitudinal effect of following the diet, whereas most people on a keto-like diet tend to follow it intermittently for shorter periods of time.
The majority of the participants, 73%, were women, which Iatan says is “very interesting to see, but also supports the available literature that women in general tend to follow more dietary patterns, tend to be more interested in to change their lifestyles. ”
Asked if there were any groups that weren’t harmed by following a low-carb diet, Iatan said how long people have been on the diet and whether or not they lose weight “can counteract any elevation in LDL.”
“The important thing to remember is that each patient responds differently. So there really is inter-individual variability between the response. What we found is that, on average, patients tend to increase their LDL cholesterol levels,” she said.
Most health experts say that the fad keto diet, which bans carbs so your body burns fat for fuel, cuts out healthy foods like fruits, beans and legumes, and whole grains. On the ketogenic diet, you limit your carb intake to just 20 to 50 per day; the lower the better. To put it in perspective, a medium banana or apple has about 27 carbs—the daily allowance.
Keto is short for ketosis, a metabolic state that occurs when your liver begins using stored fat to produce ketones for energy. The liver is programmed to do that when your body loses access to its preferred fuel, carbohydrates, and thinks it’s starving.
The ketogenic diet has been around since the 1920s, when a doctor stumbled upon it as a way to control seizures in children with epilepsy who were unresponsive to other treatment methods.
Low-carb diets like keto rely heavily on fat to fill you up. At least 70% of the ketogenic diet will be made up of fats; some say it’s more like 90%.
While you can get all that fat from healthy unsaturated fats like avocados, tofu, nuts, seeds, and olive oil, the diet also allows for saturated fats like lard, butter, and coconut oil, as well as whole milk, cheese, and mayonnaise. Eating lots of foods high in saturated fat increases the body’s production of LDL cholesterol, which can build up inside the arteries and restrict blood flow to the heart and brain.