Low Carb Diets Found to Feed Heart Disease

Written By Michael Greger M.D. FACLM on May 19th, 2015

People going on low carb diets may not see a rise in their cholesterol levels. How is that possible? Because weight loss by any means can drop our cholesterol. We could go on an all-Twinkie diet and lower our cholesterol as long as we didn’t eat too many. A good cocaine habit could do it. Anything that drops our weight can drop our cholesterol, but the goal isn’t to fit into a skinnier casket; the reason we care about cardiovascular risk factors like cholesterol is because we care about cardiovascular risk, the health of our arteries.

Now we have studies that measure the impact of low carb diets on arteries directly, and a review of all the best studies to date found that low-carb diets impair arterial function, as evidenced by a decrease in flow-mediated dilation, meaning low-carb diets effectively stiffen people’s arteries. And since that meta-analysis was published, a new study found the same thing: “A dietary pattern characterized by high protein and fat, but low carbohydrate was associated with poorer peripheral small artery function,” again measuring blood flow into people’s limbs. But peripheral circulation is not as important as the circulation in the coronary arteries that feed our heart.

There has only been one study ever done measuring actual blood flow to the heart muscles of people eating low-carb diets. Dr. Richard Fleming, an accomplished nuclear cardiologist, enrolled 26 people into a comprehensive study of the effects of diet on cardiac function using the latest in nuclear imaging technology–so-called SPECT scans, enabling him to actually directly measure the blood flow within the coronary arteries.

He then put them all on a healthy vegetarian diet, and a year later the scans were repeated. By that time, however, ten of the patients had jumped ship onto the low carb bandwagon. At first I bet he was disappointed, but surely soon realized he had an unparalleled research opportunity dropped into his lap. Here he had extensive imaging of ten people before and after following a low carb diet and 16 following a high carb diet. What would their hearts look like at the end of the year? We can talk about risk factors all we want, but compared to the veg group, did the coronary heart disease of the patients following the Atkins-like diets improve, worsen, or stay the same?

Those sticking to the vegetarian diet showed a reversal of their heart disease as expected. Their partially clogged arteries literally got cleaned out. They had 20% less atherosclerotic plaque in their arteries at the end of the year than at the beginning. What happened to those who abandoned the treatment diet, and switched over to the low-carb diet? Their condition significantly worsened. 40% to 50% more artery clogging at the end of the year.  In heart scans of the patients, as seen in my video, Low Carb Diets and Coronary Blood Flow, the yellow and particularly red areas represent blood flow through the coronary arteries to the heart muscle. The scan of one of the patients who went on a plant-based diet, shows how their arteries opened right up increasing the blood flow. Another person, however, started out with good flow, but after a year on a low-carb diet, they significantly clogged down their arterial blood flow.

So this is the best science we have, demonstrating the threat of low-carb diets, not just measuring risk factors, but actual blood flow in people’s hearts on different diets. Of course the reason we care about cardiac blood flow, is we don’t want to die. Another meta-analysis was recently published that finally went ahead and measured the ultimate end-point, death, and low-carb diets were associated with a significantly higher risk of all-cause mortality, meaning living a significantly shorter lifespan.

The reason I have so few videos about low-carb diets is that I already wrote a book about it. Carbophobia is now available free online full-text at AtkinsFacts.org. Atkins’ lawyers threatened to sue, leading to a heated exchange you’re sure to enjoy that I reprint in the book. I did touch on it Atkins Diet: Trouble Keeping it Up, though low carb diets don’t necessarily have to be that unhealthy (see my video Plant-Based Atkins Diet).