"the vegan diet is the only one shown to reverse heart disease", so right, the floor is yours. i've
heard also this in slightly different variations, plant-based diet, or a healthy plant-based diet
is the only one shown to reverse heart disease, different variations but people are essentially
referring to the same thing, and this stems from the Ornish lifestyle heart trial and the Esselstyn
report, and basically there's a number of caveats to these studies when you look at them
that don't really allow us to say that there is a reversal of heart disease, or a regression,
in the cardiovascular literature it's usually referred to as regression but it's essentially the
same idea, that the plaque is getting meaningfully smaller, and the focus tends to be on clinically
meaningful, so that it actually makes a difference clinically and in terms of risk,
so there's a number of concerns with these studies as justification to make this claim,
one is the design of the studies, so Esselstyn is not a trial per se, it's a case series,
so he's basically reporting his observations and the outcomes of his patients that he advised
that they should do this diet. there's no control group per se, there's a group that he
used as sort of a control that's essentially the group of people that did not adhere to the diet,
that did not want to or could not stick to his prescriptions, he's looking at them and saying,
look, these people had a higher rate of heart attacks and strokes than the group who did stick
with my my diet. there's nothing wrong with with him reporting those cases, it's great,
more doctors should do it, however, when we look at this type of evidence we have to analyze it
objectively, and there's a lot of confounders when something is structured this way, because
someone who can't stick with the diet, who falls off the wagon or won't stick with the
diet is also less likely to follow other type of health advice, also less likely to exercise,
more likely to smoke... at first glance, the interpretation would be, okay, so people
had these outcomes, they did better because they ate this diet. and that could be true,
we're not saying that that's ruled out, however because there are all these potential confounders,
it could also have little or nothing to do potentially with the diet,
right? these are all possibilities that we have to consider. these confounders
are always potentially present, so what you do is, depending on the design of the experiment,
you either adjust for them statistically, if it's a cohort study you're going to assess all
of those, who smokes and how much, exercise, bmi, education, socioeconomic status, all those things
are going to be recorded and then you're going to adjust statistically with multi-variable analysis
and you're going to get a sense of whether the effect of the diet still survives.
and here, because it's a case series, there's no such process so the confounders are
essentially unadjusted for. the other good way to address that is by doing a randomized trial,
you take your ideally homogeneous pool of volunteers, you randomly assign them to
the diet and the control group, and that is a more reassuring way of minimizing confounders.
so those are some of the concerns with Esselstyn. now, on that note, Ornish,
the lifestyle heart trial has a more robust design because it is a randomized controlled trial.
caveats are, pretty small number of participants,
not the end of the world, multi-pronged, so there were multiple interventions, it was four or five
interventions, so it was a diet, an exercise program, a relaxation/ meditation program,
reducing or stopping smoking, they lost weight, quite a bit compared to the baseline and to the
control group... so again, we have a multitude of things, if we wanted to say that this program had
a benefit in terms of the outcomes, i think that's fair to say, but to conclude that it's the diet
specifically, very difficult to sell that. so there's just too many things considered,
there's too many things used as an intervention for them to single one out of the five.
right. it's a multi-pronged intervention. and again, this is not to bash Ornish, this was the
experimental design, they didn't set out to prove specifically that the diet did it, they set out to
get the result, to get the best odds of improving outcomes and stopping growth of plaque or even
getting some reversal of plaque, right? so they threw everything they had at these people.
this is very common, the misunderstandings and the disagreements are often not on the data, it's the
interpretation of the data. so we should just be careful not to overstate it. the other thing
that is sometimes forgotten is that the ornish, the lifestyle heart trial wasn't a vegan diet,
it was a moderate vegetarian diet, so it had some dairy in there,
sometimes people forget that and go as far as saying it's the vegan diet, it has to be vegan,
if it's not a vegan diet you can't... that's not supported by the ornish trial, right?
so bottom line, it's possible that the diet is having that effect but we just can't say based on
the evidence, it's possible that five or ten years from now more results will nail that a vegan diet
or a plant-predominant diet is sufficient to get these results, so right now i think we should be
agnostic with regards to the granularity, not the general idea of a plant-rich diet. to be clear,
you're not making the claim that the diet didn't cause the heart disease reversal,
you're saying that we don't have enough reason to believe that it did. yeah, exactly. it's not
convincing. i'm not convinced that the diet alone did it. it's possible. it's certainly possible,
we just don't have the evidence to say that, and certainly to say that it was a vegan diet that
did it and that only a vegan diet could do it, that is really a stretch. a couple more things:
the technique, without getting too into the weeds, the technique that was used, the imaging technique
is angiography. basically you're getting an image of the outline of the lumen of the artery and not
a measurement or a visualization of the plaque per se, and so there's some uncertainty there as well,
angiography gives you sort of a surrogate and sort of a guesstimate of plaque,
but it's not a reliable measurement of plaque, so if you see the, it's called the stenosis,
right? the narrowing of the artery where the plaque presumably is, and you can see that
widen a bit over time with a treatment, but there's more than one way that that can happen.
yes, the plaque could be shrinking, the artery could be dilating, there's even technical reasons,
the angle at which you're visualizing the artery could influence that as well, so there's just some
uncertainty there with the technique. there are more recent techniques that are used now in statin
trials and things like that that specifically look at the plaque and can measure the plaque more
accurately. there is also some specific criteria in the literature that are thresholds for where
it's considered clinically meaningful regression of plaque, and it's pretty hard to cross those,
even the the statin trials, most of them don't reach that bar, and these diet trials don't
even get close to that bar of really compellingly showing a reduction in plaque that is clinically
meaningful. another thing that's interesting to note, when people say the vegan diet is the
only one that has this effect, there have been other interventions, there's one actually that
was published last year, this large trial called CORDIOPREV, and they use the mediterranean diet,
classical mediterranean, right? not what people are eating nowadays in the mediterranean region,
right? not the mcdonald's and everything, but what's normally referred to as the mediterranean
diet in the literature and the classical mediterranean, with whole foods, lots of fruits
and vegetables, some dairy, olive oil, low in red meat, low in processed foods, etc. this was a very
large trial, a thousand volunteers over seven years, massive trial, and they used ultrasound
in the carotid arteries in the neck and there was a suggestion of a reduction in plaque size.
i would not claim that the mediterranean diet reversed heart disease, i think that would be
a bit of a stretch as well, but you see what I'm saying, if we're gonna claim that the suggestion
of reduction of plaque in the ornish trial proves reversal we have to admit these things as well,
we can't kind of gerrymander. let me see if i also understand this correctly, you said that
the ornish trial wasn't even a vegan diet, it was a vegetarian. yeah, the lifestyle heart trial,
i'm pretty sure was a moderate vegetarian diet, so it was largely plant-based, plant
predominant and it had some dairy in there. okay, so not only was it not even a vegan diet but to
use this trial is to also indirectly accept this mediterranean trial which also wasn't even a vegan
diet, because they included some amounts of... right. yeah, both both diets are plant-rich,
plant-predominant, maybe that's even fair to say,
the ornish diet almost certainly is getting more calories from plants than the mediterranean diet
but otherwise in terms of this suggestion of regression of plaque i think they're about
the same, someone who's a specialist in imaging might disagree, might think one technique is more
compelling than the other, to me it's not clear that one is super convincing and the other is not.
really important, a lot of this discussion on plaque size kind of misses the big picture, which
is the actual outcomes, right? at the end of the day, and this is very common in nutrition debates
and nutrition controversies and disagreements, is people harp on things that aren't necessarily the
biggest question that we have to answer. so plaque progression and speed of plaque progression,
that's absolutely relevant but at the end of the day what you care about is outcomes,
the risk of having a heart attack, a stroke, revascularization, of dying of coronary heart
disease. that's the million dollar question, and so, both the ornish trial and for example this
CORDIOPREV trial showed an improvement in symptoms and improvement in outcomes for these
plant-predominant diets, there's no reasonable doubt that healthy lifestyle including a diet
rich in unprocessed plant foods is a pillar of prevention and management of cardiovascular risk,
there's no real doubt about that, and the potential that these things have,
it's just that extra stretch of saying that it has to be 100% vegan otherwise you're killing yourself
and that only the vegan diet has shown this and not that, that's a little bit of an overstatement