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Transcript
Preventive Medicine Column
March 24, 2017
The Case(s) for Veganism
As I write this, I am about to leave for Boston to speak at iV, the Ivy League Vegan Conference, at
Harvard. Prominent voices will gather there and collectively, one anticipates, make the case for veganism.
The timing is a bit ironic. A paper was just published in the Lancet, describing the lifestyle and
health status of the Tsimane. The paper generated considerable excitement, and widespread media attention,
because the Tsimane, a population in the Bolivian Amazon described as living “a subsistence lifestyle of
hunting, gathering, fishing, and farming,” were found to have “the lowest reported levels of coronary artery
disease of any population recorded to date.”
The Tsimane, obviously, are not vegans, as the references to both hunting and fishing indicate. On
the other hand, they are not hunting for meat in the supermarket, as I pointed out to one correspondent who
sent me the study and asked if his penchant for meat was now exonerated. My answer was perhaps, provided
it was satisfied by advent of bow and arrow and involved no cellophane.
The Tsimane, in common with our Stone Age ancestors, eat the meat of wild animals and fish they
obtain the hard and old-fashioned way. Those animals, in turn, get their food the hard and old-fashioned way,
too; they are not fed copiously in captivity. Consequently, their own bodies are lean, and represent the fats
they derive from their food sources. The result is that the Tsimane diet has virtually no trans fat, is very low
in saturated fat, and is quite low in total fat. The study authors report a diet that is 72% carbohydrate, 14%
fat, and 14% protein.
Of course, this diet made up of foods direct from nature is very low in simple starches, and sugars as
well. The authors note that the carbohydrate sources in the Tsimane diet are generally complex, and high in
fiber- just as vegetables, fruits, whole grains, beans, lentils, nuts, and seeds are. These, of course, are the
plant foods all but universally recommended for health promotion.
While the inclusion of meat in the Tsimane diet, conjoined to stunningly low levels of atherosclerosis
demonstrated by CT imaging of the coronary arteries, might seem a rebuke to vegan diet advocacy, it is a
mild rebuke at most. The nutrient composition of the Tsimane diet is much more akin to high-quality vegan
and vegetarian diets than to anything remotely like the meat-heavy diets that prevail in the U.S. and many
industrialized countries.
But even a mild rebuke, born of evidence, may deserve respect and certainly warrants reflection.
I have long noted, with all due respect to the ardent vegans among my colleagues, that we lack evidence to
prove that any one specific diet is the singular “best” for human health. This should come as no surprise
when you consider what kinds of studies would be needed to generate such evidence: randomized trials of
optimized versions of competing diets in large populations over a span of decades with incident disease and
mortality the outcome measures. The diet producing the greatest combination of longevity and vitality would
be the winner. Such a study has not been done, and don’t hold your breath.
What we do know, from a veritable sea of confluent evidence, is the basic theme of the optimal diet
for Homo sapiens. Famously described by Michael Pollan as “food, not too much, mostly plants,” it is just
so: a diet of minimally processed, wholesome foods, mostly plants, in any balanced and sensible combination.
The Tsimane diet represents such a combination. So do the Blue Zone diets, encompassing traditional
Mediterranean, Asian, vegetarian, and omnivorous variants.
I can’t support the argument I sometimes hear from colleagues that a vegan diet is “best” based on
human health considerations alone. There are, however, considerations other than our own health. There are
arguments for veganism related to ethics, the decent treatment of our fellow species, and the avoidance of
exposure to harmful food contaminants. There are compelling environmental arguments as well. The domestic
production of meat, and beef in particular, is associated with high environmental impact in every area of
importance: water consumption, land allocation, greenhouse gas emissions, and biodiversity.
This, then, is the message I am taking to the iV conference, as I add my voice to a chorus singing the
praises of well practiced veganism. We are omnivores, and we have choices. A good vegan diet is not the
only option for health promotion, but it is among the best. When the case is broadened from the health of
people to that of the planet, too, the case for veganism is very much fortified. After all, the Tsimane are few;
we are many.
-fin Dr. David L. Katz;www.davidkatzmd.com; founder, True Health Initiative