Many people think they are doing something good for their health with a low carb high fat diet. However, adherence to a low-carbohydrate, high-fat so-called ketogenic diet has now been associated with an increase in LDL and a 2-fold increased risk of cardiovascular events in a new observational study.
Bad news for followers of the popular low-carb, high-fat keto diet (LCHF). A prospective analysis confirms that this dietary pattern is associated with a significant increase in LDL cholesterol levels and an increase in incident cardiovascular events. “Our study found that regular consumption of a self-reported low-carbohydrate, high-fat diet was associated with elevated LDL cholesterol, or so-called “bad” cholesterol, and a higher risk of heart disease,” reports Iulia Iatan, attending physician-scientist at the Healthy Heart Program Prevention Clinic, St. Paul’s Hospital and University of British Columbia’s Centre for Heart Lung Innovation in Vancouver, Canada, and lead author of the study.
LCHF diets, in which ketosis is induced by consuming more protein and fat and less carbohydrate, are growing in popularity, with proponents reporting positive effects on obesity, diabetes and epilepsy, Iatan added. However, several case reports have shown that adherence to these diets leads to an increase in cholesterol levels in a number of populations, including highly trained athletes, leading some to conclude that hypercholesterolemia may not be as harmful in people who strictly adhere to a ketogenic diet. “There is a perception among patients and some members of the public that, despite the increase in LDL, there is nothing to worry about because it is part of the expected metabolic adjustment to diet,” says Liam R. Brunham, professor in the Department of Medicine at the University of British Columbia, Vancouver, Canada, and another lead author of the study. “This is probably not something that can be ignored, though,” Brunham further cautions.
Significantly increased LDL-C levels on a keto diet.
For the study, information on diet, estimated nutrient intake, and blood samples were obtained from the UK Biobank. A total of 1525 participants (mean age 54 years; 73% women) were included in a gender-specific analysis: Of these, 305 subjects followed the LCHF diet used in the study (<100 g carbohydrates per day or a carbohydrate content of <25% plus ein Fettanteil von>45%). These individuals were compared with 1220 subjects matched for age and sex who, according to the survey, ate a standard diet.
According to their own data, participants on a standard diet generally consumed more calories: 1992 kcal/day compared to 1450 kcal/day in the LCHF group. As expected, the average carbohydrate intake, expressed as a percentage of daily intake, was half lower in the LCHF group, while the percentage intake of proteins and fats was significantly higher and more concentrated on animal sources. Mean percent cholesterol intake represented less than 0.1% of total daily intake for participants on the standard diet, compared with 0.31% for the LCHF group.
During follow-up, LDL cholesterol levels remained lower (3.64 vs. 3.80 mmol/L; p=0.004) and triglycerides higher (1.53 vs. 1.34 mmol/L; p<0.001) in the standard diet group than in the LCHF group. Total cholesterol, non-HDL cholesterol, and apolipoprotein B were also significantly elevated in the LCHF group.
Association with increased cardiovascular risk.
The number of atherosclerotic cardiovascular disease (ASCVD) was also higher in the LCHF group. Over a period of up to 11 years, 9.8% of the LCHF group and 4.3% of those on the standard diet had an ASCVD event (p<0.001), an observation that persisted after adjustment for common CVD risk factors such as diabetes, smoking, obesity, and hypertension.
In an additional analysis stratified by LDL cholesterol levels, LCHF participants with the highest cholesterol levels (>5 mmol/L) had more than six times the risk of ASCVD compared with standard diet participants with LDL cholesterol levels of less than 3.5 mmol/L. Participants on a standard diet whose cholesterol levels were in the same range of >5 mmol/L did not have a significantly increased risk of ASCVD.
Is low carb high fat unfairly popular?
The study could not prove causality, Iatan stressed. “Overall, however, based on the results of our primary and secondary endpoints, we show that in a population-based cohort of British ancestry, habitual consumption of a self-reported low-carbohydrate, high-fat diet was associated with increased LDL cholesterol levels, increased ApoB levels, and increased risk of ASCVD events,” Iatan concluded.
Brunham pointed out that there are no prospective, randomized trials of ketogenic diets looking at effects on lipid profiles and cardiovascular disease. “Our study shows that there is at least reason to believe that this dietary pattern may increase cardiovascular risk,” Brunham points out. “The message for people on this diet, or for physicians with patients on this diet, is that lipid levels should be closely monitored, and if they develop severe hypercholesterolemia, their cardiovascular risk factors should be closely monitored and perhaps a shift away from this diet should be considered.”
Source: Iatan I: Association Of A Low-carbohydrate High-fat (Ketogenic) Diet With Plasma Lipid Levels And Cardiovascular Risk In A Population-based Cohort, Featured Clinical Research II, ACC Congress 2023.
CARDIOVASC 2023; 22(3): 24 (published 9/15/2013, ahead of print).
