• Kenneth Civello, MD

Ketogenic Diet: A Cardiologist Perspective

Every day a patient will ask me, “What type of diet should they be following to prevent heart disease?”


My answer has always been the Mediterranean diet, which numerous studies have proven is the best diet for a healthy heart. Despite the overwhelming data showing cardiovascular benefits with the Mediterranean diet, I commonly get the question


“What about the Keto diet, Ketogenic Diet, High Fat/ Low Carb Diet?"

My initial reaction is to dismiss it as a fad diet, but before I rejected the Ketogenic diet, I first wanted to read and research it.


To my surprise, this diet was not a new fad. It was a diet that was used in 1863 by Sir Willliam Banting as a primary method to lose weight. Later, Dr. William Osler who many consider being the "Father of Modern Medicine" used a High fat/ Low Carbohydrate diet to effectively treat Diabetes Mellitus.


What was the recommendation of the High Fat/ Low Carbohydrate Diet published by Dr Banting and Osler?

The answer: 75% Fat, 20% Protein, and 5% Carbohydrates.

Pretty close to the exact percentages that the "Fad" Keto diets recommended in 2018.


How did medicine forget this diet and why did we start to demonize fat? I imagine everything dates back to the 1960s when the sugar industry paid scientists to play down the link between sugar and heart disease. We have had five decades of research into the role of nutrition and heart disease that may have been primarily shaped by the sugar industry. For those interested, you can read, How the Sugar Industry Shifted Blame to Fat.


Despite the hundred-year-old data published by Dr. Osler. My concern as a Cardiologist was "What does all this fat do to blood cholesterol?"

Thankfully, modern-day scientists have looked and published research that provides some interesting but not common sense answers.


Before we explore the research on lipids, you need to know a couple of terms:

  1. HDL Cholesterol (Good Cholesterol). Think of it as the “healthy” cholesterol, so higher levels are better. HDL should be High. Experts believe HDL acts as a scavenger, carrying LDL cholesterol away from the arteries and back to the liver. There it’s broken down and passed from the body.

  2. LDL Cholesterol (Bad Cholesterol). A low LDL cholesterol level is considered good for your heart health. LDL should be Low. Think of it as less desirable or even lousy cholesterol, because it contributes to fatty buildups in arteries (atherosclerosis). Plaque buildups narrow arteries and raise the risk for heart attack, stroke, and peripheral artery disease can narrowed arteries in the legs).

  3. Triglycerides. Most common type of fat in the body; they store excess energy from your diet. A high triglyceride level combined with low HDL cholesterol or high LDL cholesterol is linked with fatty buildups in artery walls. This increases the risk of heart attack and stroke.

  4. Metabolic Syndrome. Metabolic syndrome occurs when a person has 3 out of 5 of the following

  • High Triglyceride level

  • Low HDL

  • Obesity, Elevated blood pressure and glucose.


The Metabolic syndrome can double your cardiovascular risk of heart disease.


So when we look at the Ketogenic diet and Low Carbohydrate Diet, we need to realize that it tends to help those with the Metabolic Syndrome since the research has demonstrated that the it lowers triglycerides and increases HDL (Good Cholesterol). Since HDL increases and Triglycerides decrease, this may result in lower risk of cardiovascular disease.


The Mediterranean Diet, also raises you HDL and lowers triglycerides but not as much as a Low Carbohydrate diet. See figure below from Comparison of Weight Changes using Low-Carbohydrate, Mediterranean, or Low-Fat Diet. Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet. N Engl J Med 2008; 359:229-241



When following a low fat diet a lower LDL will decrease your cardiovascular risk but if you overdo it with the carbohydrates since you are not eating fat, the increased weight gain and development of Metabolic Syndrome may offset the benefits of the LDL lowering. See figure below for diets effects on weight loss.




In the end, common sense is not always common, an article published by Forsythe showed us that our common sense thoughts that High-Fat diet will lead to High Fat in the blood were wrong. It turns out that when you are on a High-Fat diet, you burn fat as fuel, so you have lower levels of saturated fat in the blood.


Is all of this confusing for patients and physicians? Yes.

We need more research on diet, but I can see the tide continuing to shift toward increasing good fats (vegetables, nuts, seeds, and fish) and away from processed carbohydrates.


My primary concern is eating a ketogenic diet may be hard for some to follow and the avoidance of a lot healthy fruits and vegetables does worry me over the long term.


I still believe in the Mediterranean diet, but the Keto diet is not a fad and may be effective alternative to low-fat diets. Personal preferences and metabolic considerations might allow physicians and nutritionist to individualize dietary interventions based on their genetic makeup, weight, and medical conditions.


References 1. Limited Effect of Dietary Saturated Fat on Plasma Saturated Fat in the Context of a Low Carbohydrate Diet. LIPIDS Volume 45, Issue 10, October 2010, Pages: 947–962 2. Comparison of Low Fat and Low Carbohydrate Diets on Circulating Fatty Acid Composition and Markers of Inflammation. LIPIDS Volume 43, Issue 1, January 2008, Pages: 65–77 3. Carbohydrate Restriction has a More Favorable Impact on the Metabolic Syndrome than a Low Fat Diet LIPIDS Volume 44, Issue 4, April 2009, Pages: 297–309 4. Dietary Intervention to Reverse Carotid Atherosclerosis Circulation. 2010;121:1200-1208 5. Dietary Fats and Cardiovascular Disease: A Presidential Advisory From the American Heart Association. Circulation. 2017 Jul 18;136(3)


Studies Demonstrating Diet Effects on Weight Loss on Obesity N Engl J Med 2008;359:229-241 Nordmann et al., Arch Intern Med 2006;166:285-293 Hession et al., Obesity Reviews 2009;10:36-50 Santis et al., Obesity Reviews 2012;13:1048-1066 Hu et al., Am J Epidemiology 2012;176: S44-S54 Naude et al. PLOS ONE 2014;9:e100652

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