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Could a high-fat, low-carb diet similar to keto diets affect cardiovascular health? Image credit: Alejandro Moreno de Carlos/Stocksy.
  • Researchers investigated whether high-fat, low-carbohydrate, keto-like diets increase cardiovascular risk.
  • Keto-like diets were linked to twice as many cardiovascular events as standard diets.
  • Further research is needed to confirm the results.

The ketogenic or “keto” diet involves consuming around 10% of daily calories from carbohydrates, 30% from protein, and 60% from fat. The diet triggers a process called “ketosis,” wherein the body derives energy from burning fats rather than carbohydrates.

Some studies suggest that a keto diet can help with weight loss, make cancer cells more vulnerable to chemotherapy and radiation, and reduce blood sugar levels among those with diabetes.

Case studies, however, suggest that the keto diet may exacerbate or cause high cholesterol.

Further studies investigating how keto diets affect cardiovascular health could inform dietary options for individuals with different health profiles.

Recently, a study led by Dr. 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, assessed how low-carbohydrate, high-fat (LCHF) diets, similar to keto diets, may affect cardiovascular risk.

The research found that a LCHF diet almost doubled the risk of cardiovascular events when compared to a standard diet.

The study was presented at a conference held jointly by the American College of Cardiology and the World Heart Federation — the ACC Annual Scientific Session together with the World Congress of Cardiology.

For the study, the researchers analyzed information collected by the UK Biobank for individuals with data on serum lipids, metabolomic markers, and dietary patterns.

All participants had recorded their diet in a 24-hour food survey. Among them, 305 met the criteria for an LCHF diet, defined as consuming less than 25% of daily calories from carbohydrates and more than 45% from fat.

The researchers matched these participants with 1,220 individuals who were considered to be on a “standard diet,” and made up the control group. Participants’ average age was 54 years, and they had a mean body mass index (BMI) of around 27 — which placed them in the “overweight” category

Participants also had their blood drawn to measure their cholesterol levels. The researchers followed the participants for an average of 11.8 years.

The researchers noted that the diet is “keto-like,” due to its higher percentage of carbohydrates and lower levels of fats than a strict ketogenic diet.

During the follow-up period, 9.8% of participants on an LCHF diet versus 4.3% of controls experienced a cardiovascular event, including blockage in arteries, a heart attack, or stroke.

Those on LCHF diets had significantly higher LDL cholesterol levels and apolipoprotein B (ApoB) — a protein indicator of cholesterol levels.

“When people shift their caloric intake from carbs to fat, and especially if it is predominantly saturated fat such as from animal products, LDL cholesterol and ApoB will go up. This has been known for decades,” Dr. Liam R. Brunham, associate professor of medicine at The University of British Columbia, one of the study authors, told Medical News Today.

“What our study showed is that the effect is not uniform, but that there is a subgroup of people that will have severe hypercholesterolemia [abnormally high cholesterol levels] while on a LCHF diet. This is the group in whom the greatest increase in cardiovascular risk was observed,” he noted.

Dr. Dana Hunnes, assistant professor at UCLA Fielding School of Public Health, who was not involved in the study, told MNT that “[t]his type of diet is supposed to be used short-term, primarily in individuals who have seizure disorders or neurological disorders as ketones can pass through the blood-brain barrier.”

“A keto diet is high in saturated fats (typically), animal products, and may raise cholesterol levels and inflammation/ stress,” she explained.

“A low-carb, high-fat diet […] similarly tends to be high in animal products, saturated fats, and low in carbs and fiber. These properties can increase cholesterol levels and inflammation in the body, as well as potentially influence the microbiome and increase the risk for heart disease,” she added.

MNT also spoke with Michelle Routhenstein, a heart health dietitian at Entirely Nourished, a virtual nutrition counseling and consulting private practice. She told us that the study confirms her own observations.

“This study reiterates what I see in my private practice, [as] many individuals come to see me after being on the keto diet for several months with very high LDL and apolipoprotein A levels, two important [factors] that help establish risk for atherosclerosis,” she noted.

“The keto diet can be very high in saturated fat and low in soluble fiber, which negatively impacts both of these values,” Routhenstein cautioned.

When asked about the study’s limitations, Dr. Brunham noted that the study shows correlation but not causation.

He added that those on the LCHF and standard diet differed in characteristics such as BMI, obesity, and diabetes status, potentially skewing the results.

“In other words, it could be that people in the UK Biobank who reported consuming an LCHF diet were at greater risk of heart disease not because of the diet but because the people that choose this diet were inherently higher risk. We would need other types of studies such as randomized trials to fully understand this,” he noted.

Dr. John P. Higgins, a sports cardiologist at McGovern Medical School at The University of Texas Health Science Center at Houston, not involved in the study, added that further limitations include that diet and cholesterol levels were captured at only one time point.

He also questioned whether standard diets were really “standard” or whether they were a more healthy group overall.

“This type of study provides new insights to researchers and clinicians but should not be the basis for public policy,” cautioned Dr. Brunham.

“Given that there are still many unknowns in the field, a conservative implication would be that patients on a LCHF diet should monitor their lipid levels, and if they develop severe hypercholesterolemia should consult with a medical professional about managing their cardiovascular risk,” he added.

“I’ve been saying this for a while but, our bodies are not meant to live on ketones, and definitely not for any long periods of time,” noted Dr. Hunnes.

“These findings demonstrate that high intakes of animal products and fats seem to increase the likelihood or risk of a cardiac event; and this too, is something the science has agreed with for decades,” Dr. Hunnes added.

“The Mediterranean diet and Blue Zones diets are primarily [including] whole foods that are plant-based. We would be better served — as far as heart disease and other chronic conditions are concerned — to try and eat more like those who live in the Mediterranean or Blue Zones than a high-fat, high-protein, low-carb diet,” she concluded.