“Low Carb Diets and Coronary Blood Flow” 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. You could go on an all-Twinkie
diet and lower our cholesterol if we were unable to eat
the dozen daily Twinkies necessary to maintain your weight. That’s why a good cocaine
habit can lower cholesterol. Chemotherapy can drop
cholesterol like a rock. Tuberculosis can work wonders
on one’s waistline. Anything that drops our weight
can drop your 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. Well, now we have studies
that have measured the impact of low carb diets
on arteries directly, and a review of all the
best studies done to date found that low carb diets
impair arterial function, as evidenced by a decrease
in flow-mediated dilation, meaning low carb diets effectively
cripple people’s arteries. And since the meta-
analysis was published another 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. Peripheral circulation is great, but what about 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, and this is it. 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, 10 of
the patients had jumped ship onto the low
carb bandwagon. At first I bet
he was upset, but surely soon realized he had an unparalleled
research opportunity dropped into his lap. Here he had extensive imaging of
10 people following a low carb diet and 16 following a
healthy 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. Thanks to the kind
generosity of Dr. Fleming we can actually see the changes
in blood flow for ourselves. Here are some representative
heart scans. The yellow and particularly
red represent blood flow through the coronary arteries
to the heart muscle. This patient went on
a plant-based diet and their arteries opened right up,
increasing the blood flow. This person, however,
started out with good flow, but after a year on
a low carb diet, they significantly clogged
down their arterial blood flow. This is the best
science to date, 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, and a meta-analysis was
recently published that finally went ahead and
measured the ultimate end-point, DEATH… and low-carb diets were associated
with significantly higher risk of all-cause
mortality, meaning low carbers living a
significantly shorter lifespan.