We've received a number of questions and comments from a video Michael Greger MD put out yesterday. In the video, Dr. Greger states that “vegan couch potatoes” may have healthier carotid arteries than long distance runners who average 2,500 miles a year.
Is that correct? As a vegan, does this apply to you?
Well the study Dr. Gerger cities only applies to vegans eating a very special vegan diet – an unprocessed, calorie-restricted, low protein, low saturated fat, and 100% raw diet.
This is not your average “vegan couch potato” diet, and the researchers doing the study think it was the low calorie intake (CR) and the low protein nature of the diet that was largely responsible for the healthier carotid arteries, rather than the fact that the diet was vegan.
So unless you are eating a very healthy vegan diet – unlike the diet eaten by most vegans – Dr. Greger's video doesn't apply to you.
Here is a link to the full study Dr. Greger cites in his video. It was published 5 years ago by Luigi Fontana PhD, and it titled, “Long-term low-protein, low-calorie diet and endurance exercise modulate metabolic factors associated with cancer risk.” http://ajcn.nutrition.org/content/84/6/1456.long
Dr. Fontana, who is not vegan but follows a low-protein, calorie-restricted diet, discussed this study 5 years ago after it was published, at one of Dr. McDougall's Advanced Study Weekends.
As you can see from the study, the 21 vegan subjects were consuming “a low-protein, low-calorie diet composed of raw plant-derived foods and no processed foods,” for 2 or more years. The athlete group in the study, on the other hand, was eating the terrible Standard American Diet (SAD), had higher intakes of saturated fat, trans fat, much lower fiber, and a much higher intake of calories.
What this study actually shows most strongly is that even though the athletes were running an average of 48 miles a week and keeping their weight low as a result of that activity, they were unable to run off the bad heart disease effects of the SAD diet. You can't run your way to good health, if you're eating a bad diet.
It's interesting to compare the low-protein diet of the raw vegans in the study linked here: http://ajcn.nutrition.org/content/84/6/1456/T1.expansion.html – with the diet that the average vegan eats, linked here: http://www.veganhealth.org/articles/nutrientintakes (the studies in the second link are the two largest studies of vegans and vegetarians done to date, EPIC and AHS-2).
It's great to think that a “vegan diet” automatically protects you against heart disease – but the truth is it doesn't.
What can protect you, according to the scientific literature, are specific diets like the Pritikin Diet (which is not even a vegetarian diet), the Dean Ornish MD Diet (which is not a vegan diet), Dr. McDougall's or Dr. Esselstyn's Diets (which are vegan).
Although the number of healthy vegan eaters is growing, most vegans are not following these specific diet programs, as you can see by the average diet information for the EPIC and AHS-2 diets, linked above on veganhealth.org.
So when someone says “the vegan diet prevents heart disease” or “vegan couch potatoes have healthier arteries than marathoners,” it may be technically true in some people eating a very specific vegan diet, but it's not totally accurate.
The risk is that many people watch a video like this, thinking it is spotlighting a study about the generic “vegan” or “plant-based” diet, and they think, “Wow, I am getting incredible health benefits just from being vegan!” But since they are not eating a calorie-restricted raw vegan diet, or a McDougall or Ornish or Pritikin diet, the benefit from highlighted study doesn't actually apply to them.
It would be incredibly useful if videos like this actually spotlighted the particular diet from the study that produced a benefit, rather than just saying “a vegan diet” or “a plant-based diet.” By doing that, the public could be better educated about how they could get a benefit, by adopting the specific diet that delivered the benefit in the study, rather than touting “the vegan diet” as the presumed reason for the benefit (when the lack of animal products was just one aspect of the diet, and probably not the key one).
The devil is always in the details.
So this is the take-home message: when someone tells you “a vegan diet” or “a plant-based diet” can deliver this or that benefit, the question has to be: “Well what exactly were they actually eating?”
You may find it wasn't even a vegetarian diet, or that it was a special 100% raw, low-protein calorie-restricted diet, or a specific program of one of the doctors or organizations, which have conducted and published research on their dietary programs.
The truth is, the average “vegan diet,” according to research linked above, may not be all that healthy, and not much healthier than a non-veg diet. If you look at the Adventist Health Study (AHS-2), for example, you see that researchers called fish-eaters and occasional meat-eaters “vegetarian” for the purposes of the study, and in order to show a benefit. When meat-eaters and fish-eaters are removed and not included as “vegetarians,” there was no health benefit from the vegetarian diet compared to the non-veg diet, see: http://www.vegsource.com/news/2013/06/dont-go-vegetarian-or-vegan-for-health-benefits.html
A diet is not automatically healthy just because it's vegan.
Eliminating animal products is only one step in the right direction. Eliminating or minimizing processed vegan foods, saturated fat, salt, sugar, oils, concentrating on low calorie density, and so forth – principles found in certain plant-based diet programs – these are crucial if health is your objective.