Low-carb diets don’t accelerate coronary calcification

coronary artery plaque

We have heard it time and time again. High-fat diets cause heart disease. Sure, they improve metabolic syndrome, insulin resistance and diabetes… they lower blood pressure and improve weight loss. But they might cause heart disease, so we shouldn’t recommend them.

Sometimes this sort of “logic” makes me ashamed to call myself a doctor.

Fortunately that debate is actively changing.

I was optimistic that a recent study on coronary artery calcification (CAC) and low-carb diets was going to speed up that change. Unfortunately, that doesn’t seem to be the case.

The study was just published in The British Journal of Nutrition and is the first to investigate whether or not low-carb diets are associated with the progression of cardiovascular disease as measured by CAC score. A CAC score is a simple, non-invasive test using a CT scan. It takes about 10 seconds, has a low level of radiation (about the same as a mammogram) and tells us if there is any calcium in the walls of the arteries in and around your heart. Although it does not tell us if you have blockages inside your arteries, it is an excellent marker of the presence of coronary artery disease and a very good predictor for risk of heart attacks in the next 10 years.

This was a prospective, observational study (a weak level of evidence based on Diet Doctor’s policy for grading scientific evidence) where they enrolled over 5,000 individuals, average age 63, and followed them with a baseline CAC and a repeat study 2.4 years later. They collected data about fat and carbohydrate consumption and in the end, they found no difference between the various levels of carbohydrate or fat intake in terms of development or progression of CAC.

British Journal of Nutrition: Low-carbohydrate diets and prevalence, incidence and progression of coronary artery calcium in the Multi-Ethnic Study of Atherosclerosis (MESA)

While on the surface this seems like it should exonerate low-carb diets of any cardiovascular concern. Unfortunately, this wasn’t the study to set the record straight.

For starters, they relied upon food frequency questionnaires, the same unreliable method that many nutritional epidemiology studies use.

Secondly, the results are muddied by the same confounding variables and healthy-user biases from which all epidemiological studies suffer.

Thirdly, the lowest carbohydrate cohort ate less than 43% of their calories from carbohydrates and more than 40% from fat, and the highest carbohydrate group ate more than 65% from carbohydrates and less than 22% fat. Those percentages don’t truly represent those following a very low-carb, ketogenic diet or even a moderately low-carb diet (less than 100 grams of carbs per day).

Finally, 2.4 years is too short of a follow-up period to realistically reach conclusions about coronary disease progression based on CAC.

Although this may be an encouraging start, higher-quality, longer-term studies that investigate the effects of a well-formulated ketogenic diet are needed to ultimately answer this question. In the meantime, the best evidence we have on the safety of a low-carb diet is its effect on surrogate markers such as blood pressure, insulin resistance, metabolic syndrome, HDL and triglyceride levels, size of LDL particles and others.

For me, that’s good enough to keep recommending low carb to most of my patients.

Thanks for reading,
Bret Scher MD FACC

Earlier

Management of blood cholesterol just got personal

Diabetes and heart health: Know your risk

Cholesterol deniers or statin pushers — is there a middle ground?

Heart disease

6 comments

  1. Pat
    What are your thoughts on daily aspirin use.. my husband had hypertension and was on medication, now since going low carb has come off it, but is not sure if aspirin is still needed
    Reply: #4
  2. Lauren
    Thanks for yet another clear, balanced review of the science. Dr Scher is a great addition to the Diet Doctor team.
  3. Carol
    Unfortunately they are looking in the wrong places. It’s a gut disbiosis....microbes not making K2 ....K2 not putting calcium in the right places ie bones problem. We have got my husbands score down by 300 in a year through a lot of research and a combination of strategies including driving insulin down with Keto, IF, fixing a lifetime of gut disbiosis, K2, vit D. I made the connection by coming at it from the other direction....why was my CAC score ok and my husbands stratospheric? Lightbulb moment....I’ve got perfect digestion whereas ......my husbands is terrible.....after a bout of disentry In Asia in his 20’s, the drugs stripped his bowel flora and so began a lifetime of terrible disbiosis.....the story continues but I think we’re making good progress and he will make it to 70 this year so his odds of not dropping dead are improving by the minute.
  4. Kristin Parker Team Diet Doctor

    What are your thoughts on daily aspirin use.. my husband had hypertension and was on medication, now since going low carb has come off it, but is not sure if aspirin is still needed

    Please encourage your husband to work with his doctor regarding medication and dosage.

  5. Cassieoz
    Thanks Brett for being sceptical of a study that could have been co-opted to support keto. Too many of the keto media heroes rightly reject weak research whose conclusions they disagree with, only to embrace poor weak anectdotal stuff that agrees with their own dogma. My mum always told me to be sceptical of anything that told me what I wanted to hear, to the same degree as that I refuted. Keep up the good work
  6. Lawrence
    @Pat, daily low-dose aspirin found to have no effect on healthy life span in older people according to a large NIH (National Institute of Health) -funded study in United States and Australia. This large study is 3 months old. I stopped taking mine...
    https://www.nih.gov/news-events/news-releases/daily-low-dose-aspirin-...

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