Stethoscope listening to a heartbeat

Is the ketogenic diet safe for the heart?

Stethoscope listening to a heartbeat

I was asked the other day whether or not eating a low carbohydrate, high fat diet such as a ketogenic diet would be safe for the heart. My answer was YES. However, honestly, up until about two years ago this would not have been my answer.

I remember about 15 years ago when the Adkins diet was a popular diet. Some of my family and friends were on this diet and had great results with it. I however, gave them a hard time, ‘yes you will lose weight but you will die from a heart attack’.

The theory was that eating all that saturated fat would increase cholesterol levels, which would increase the risk for atherosclerosis or clogging of the arteries and then heart attacks. We have since learned that this is not true. As I discussed in another blog, it was shown that people who switched from eating saturated fat to vegetable oils, which at the time was thought to be the healthier type of fat, actually had an HIGHER risk of heart attacks and death. (Ramsden 2016) (Ramsden 2013)

Those studies however, just looked at changing the types of fat that were eaten, i.e. stopping saturated fats and start using vegetable oils, not increasing the amount of fats in the diet. So what happens to cardiac risk factors (obesity, specifically waist circumference, hypertension, diabetes, high triglycerides and high systemic inflammatory markers such as CRP) when start eating more fats and fewer carbohydrates as in low carbohydrates diet? Several studies, which were recently published, answered just that question.

The first was a study published in the journal Obesity Reviews in 2012. This study reviewed 23 studies with a total of 1,141 obese patients eating a low carbohydrate diet for weight loss. They found improvement of all major cardiovascular risk factors associated with eating a low carbohydrate diet.   Specifically, the study found a significant decreased in weight, body mass index and abdominal circumference. Systolic and diastolic blood pressures were also decreased.   Markers for diabetes were improved including, fasting plasma glucose levels, gylcated hemoglobin (HgA1c) and insulin levels. Cholesterol levels were also improved; with lower levels of triglycerides and increased levels of HDL. Lastly the marker of inflammatory, CRP levels, were also improved (Santos, 2012)

Another study looked at very low carbohydrate or ketogenic diet specifically. This study reviewed a total of 13 studies, in which a total 1577 individuals were randomized to either very low carbohydrate diet or a low fat diet. The very low carbohydrate diet group had significantly greater weight loss, improvement of diastolic blood pressures, lower triglycerides and higher HDL levels. Fasting blood glucose, insulin levels, HgA1c and CRP all showed improvement in favor of the very low carbohydrate group compared to low fat groups. (Bueno, 2013)

The LDL levels in the very low carbohydrate group were increased, as expected from eating more saturated fats. However, as discussed in a prior post, it is not the LDL particle itself that is the problem: instead, it is the size of the particle that matters. There are actually two different types of LDL based on size. There is small and large size LDL. The small LDL particles are the ones that are believed to be harmful, or more prone to cause the clogging of the arteries that is of clinical concern. When LDL is exposed to high carbohydrates and high triglycerides, it is more likely to become oxidized or damaged, making the LDL a small dense particle. Whereas, it has been shown the type of LDL particles that are elevated when the diet contains a higher saturated fat (not the inflammatory vegetable oils) combined with carbohydrate restriction, are the larger sized LDL particles, which are the less artherogenic than the small dense LDL. (Krauss, 2006)

Then lastly, a study published in the journal Circulation, used carotid ultrasound as a way to measure atherosclerosis. The participants were randomized into a low fat diet, a Mediterranean type diet or a low carbohydrate diet. After 2 years of dietary intervention, they found that all 3 groups had a significant regression of the atherosclerosis plaques. This suggested that the low carbohydrate diet is at least as effective as the other diets in showing regression. The study did not have the power to show differences between the groups, but there was a slight trend for the greatest improvement seen in the low carbohydrate diet. (Shai, 2010)   Thus, based on this study eating a low carbohydrate diet does not increase risk of atherosclerosis disease; instead it may actually decrease it.

So yes I have to apologize to my friends and family who were ahead of the game. They were right all along. Based on these studies and others, I now come to realize that going on a low carbohydrate, high fat diet such as ketogenic diet is indeed safe for the heart. Not only may the ketogenic diet help you lose weight, it may also improve your cardiovascular risk factors and does not increase your risk of atherosclerosis.

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Bueno, N. B. (2013). Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. British Journal of Nutrition (110), 1178-1187.
Krauss, R. (2006). Seperate effects of reduced carbohydrate intake and weight loss on atherogenic dyslipidemia. American Journal of Clinical Nutrition (83), 1025-1031.
Ramsden, C. E. (2016). Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from the Minnesota Coronary Experiment (1968-73). British Medical Journal, 353, 1-17.
Ramsden, C. E. (2013). Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis. British Medical Journal, 346, 1-18
Santos, F. (2012). Systematic review and meta-analysis of clinical trials of the effects of low carbohydrate diets on cardiovascular risk factors. Obesity Reviews, 13, 1048-1066.
Shai, I. (2010). Dietary Intervention to Reverse Carotid Atherosclerosis. Circulation, 121, 1200-1208.