NEW ORLEANS — Following a keto-like diet can lead to serious heart trouble, a new study warns. Eating less carbohydrates and high amounts of fat displays an association with increased cholesterol levels and twice the risk of suffering heart problems such as blocked arteries, heart attacks, and stroke. Approximately one in five Americans are on a low-carb, keto-like, or full keto diet.
“Our study found that regular consumption of a self-reported diet low in carbohydrates and high in fat was associated with increased levels of LDL cholesterol— or “bad” cholesterol—and a higher risk of heart disease,” says lead author Iulia Iatan, MD, PhD, an attending physician-scientist at the Healthy Heart Program Prevention Clinic at St. Paul’s Hospital and University of British Columbia’s Center for Heart Lung Innovation, in a media release. “To our knowledge, our study is one of the first to examine the association between this type of dietary pattern and cardiovascular outcomes.”
Carbohydrates are one of the first sources the body uses for energy. Low-carbohydrate high-fat diets like the keto diet restrict the number of carbs you eat, forcing the body to break down fat for energy instead. The breakdown of fat in the liver creates ketones, chemicals the body uses as energy when there are no carbohydrates. People who advocate for a ketogenic diet often suggest limiting carbohydrates to 10 percent of your total calories. Instead, the focus is getting 20 to 30 percent of protein and 60 to 80 percent of calories from fat.
However, previous studies have linked a low-carb high-fat diet to the highest levels of LDL cholesterol. Doctors consider LDL to be the “bad” type of cholesterol that increases the risk of heart disease from atherosclerosis — a buildup of cholesterol in the coronary arteries. Despite that, study authors note the effects of a low-carb high-fat diet on a person’s risk for heart disease and stroke have been unclear.
1 in 10 people on a keto diet had heart problems
For the study, the research team defines a low-carbohydrate high-fat diet as taking in more than 25 percent of total daily calories from carbs and more than 45 percent from fat. They used data from a public health database in the United Kingdom to gather information on people’s diets. Over 70,000 people completed a one-time, self-reported 24-hour diet questionnaire and had their blood drawn to check cholesterol levels. From that group, 305 people had a diet resembling a low-carb high-fat diet. Researchers paired these individuals with 1,220 people who reported eating a standard diet.
People on a low-carb high-fat diet showed significantly higher levels of LDL cholesterol and apolipoprotein B (apoB) — the protein component sitting on LDL and other atherogenic lipoprotein particles. Previous studies suggest an elevated apoB helps predict the likelihood of cholesterol causing heart disease. Nearly 12 years after participants filled out the original questionnaire, people on the low-carb high-fat diet had more than twice the risk for cardiac problems. These included blockages in the arteries that required stenting procedures, heart attack, stroke, and peripheral arterial disease.
Results show 9.8 percent of participants on a low-carb high-fat diet experienced a new cardiac issue compared to people following a standard diet.
“Among the participants on an LCHF diet, we found that those with the highest levels of LDL cholesterol were at the highest risk for a cardiovascular event,” Iatan explains. “Our findings suggest that people who are considering going on an LCHF diet should be aware that doing so could lead to an increase in their levels of LDL cholesterol. Before starting this dietary pattern, they should consult a health care provider. While on the diet, it is recommended they have their cholesterol levels monitored and should try to address other risk factors for heart disease or stroke, such as diabetes, high blood pressure, physical inactivity and smoking.”
Not everyone will have health problems
According to the researchers, not everyone experienced the same outcomes while following a low-carb high-fat diet.
“On average, cholesterol levels tend to rise on this diet, but some people’s cholesterol concentrations can stay the same or go down, depending on several underlying factors,” Iatan says. “There are inter-individual differences in how people respond to this dietary pattern that we don’t fully understand yet. One of our next steps will be to try to identify specific characteristics or genetic markers that can predict how someone will respond to this type of diet.”
There are several limitations to consider when drawing conclusions from this study. The first is that people only provided information on their diet at only one point in their lives. It is possible their diet changed after nearly a decade. Additionally, people self-reported data to the health questionnaire, which can be inaccurate as they over or underestimate their eating habits. The research is also an observational study, meaning the researchers cannot exclude other variables like exercise and stress that could affect a person’s health.
The researchers presented their findings at the American College of Cardiology’s Annual Scientific Session Together with the World Congress of Cardiology.