New UBC research suggests that the ketogenic or “keto” diet — a popular weight-loss diet that involves consuming low amounts of carbohydrates and high amounts of fats — may pose an increased risk to cardiovascular health.
The study, presented over the weekend at the American College of Cardiology’s annual scientific session together with the World Congress of Cardiology, found that a keto-like diet may be associated with higher levels of “bad” cholesterol and twice the risk of cardiovascular events such as chest pain, blocked arteries requiring stenting, heart attacks and strokes.
“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,” said lead author Dr. Iulia Iatan, a physician-scientist at UBC’s Centre for Heart Lung Innovation and the Healthy Heart Program Prevention Clinic at Providence Health Care’s St. Paul’s Hospital. “To our knowledge, our study is one of the first to examine the association between this type of dietary pattern and cardiovascular outcomes.”
Low-carbohydrate, high-fat (LCHF) diets, like the keto diet, restrict consumption of carbohydrates that are the body’s primary source of energy. By depriving the body of carbohydrates, it is forced to start breaking down fat for energy instead.
For the study, Dr. Iatan and her colleagues defined an LCHF diet as consisting of no more than 25 per cent of total daily calories from carbohydrates and more than 45 per cent of total daily calories from fat. They dubbed this an LCHF diet and “keto-like” because it is somewhat higher in carbohydrates than a strict keto diet. Proponents of the keto diet generally suggest limiting carbohydrates to 10 per cent of total daily calories, protein to 20-30 per cent and obtaining 60-80 per cent of daily calories from fat.
The research team analyzed data from the UK Biobank, a large-scale database with health information from over half a million people living in the United Kingdom who were followed for at least 10 years. Upon enrollment in the biobank, participants completed a self-reported diet questionnaire and had blood drawn to check their cholesterol levels.
“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,” Dr. Iatan said. “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.”
“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 and higher risk of cardiac events.”
Dr. Iulia Iatan
The study’s findings also suggest that not everyone responds to an LCHF diet in the same way.
“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,” Dr. Iatan said. “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.”
A limitation of the study is that participants provided dietary information at only one point in time, which should be considered when interpreting the study findings, Dr. Iatan said.
Because the study was observational, it can only show an association between the diet and an increased risk for major cardiac events, not a causal relationship. However, Dr. Iatan said the findings merit further research in prospectively designed studies, especially when approximately one in five Americans report being on a low-carb, keto-like or a full keto diet.