“What’s the “Natural”
Human Diet?” There are three broad theories
about evolution and food. One is that humans have
become adapted to the products of the
agricultural revolution over the last
10,000 years. Two is the
paleo view that 10,000 years is a blink
of an evolutionary eye, and that humans are adapted
to paleolithic diets with lots
of lean meat. But why stop there? The last 200,000 years as
mostly stone age humans represents just the last 1%
of 20 or so million years we’ve been evolving since
our common great ape ancestor. During our truly
formative years, the first 90% of
our existence one might say, our
nutritional requirements reflect an
ancestral past in which we ate mostly
leaves, flowers, and fruits, with some bugs
thrown in thanks to wormy apples
to get our vitamin B12. For this reason,
another approach that might improve
our understanding of the best dietary practices
for modern humans is to focus attention
not on the past, but rather on the
here and now; that is, on the study
of the foods eaten by our closest
living relatives given the bulk of our
ancestral diets and the lack of evidence supporting
any notable diet-related changes in human nutrient requirements,
metabolism, or physiology compared to our
fellow great apes. This could explain why
fruits and vegetables are not only just
so good for us, but vital to
our survival. We’re actually one
of the few species so adapted to a
plant-based diet, that we can actually die from
not eating fruits and vegetables, from the vitamin C
deficiency disease scurvy. Most other animals just
make their own vitamin C. But why would our body waste
all that effort making vitamin C, when we evolved
hanging out in the trees just eating fruits and
veggies all day long? It’s presumably not a coincidence
that the few other mammals unable to synthesize
their own vitamin C (like guinea pigs, some
bunny rabbits, and fruit bats) are all, like us great apes,
strongly herbivorous. Even during the
stone age, we may have been getting up
to ten times more vitamin C than we get today. And ten times more
dietary fiber, based on essentially rehydrated
human fossilized feces. The question is, are these
incredibly high nutrient intakes simply an unavoidable
by-product of eating whole plant
foods all the time or might they actually be serving
some important function like antioxidant defense? Plants create antioxidants to
defend their own structures against free radicals. The human body
must defend itself against the same
types of pro-oxidants, and so we have also
evolved an array of amazing
antioxidant enzymes, which is effective,
but not infallible. Free radicals can
breach our defenses, cause damage that
accumulates with age, leading to a variety
of disease, causing ultimately
fatal changes. That’s where plants
may come in. Plant-based,
antioxidant-rich foods traditionally formed the
major part of our diet, and so we didn’t
have to evolve that great of an
antioxidant system. We could just let the
plants in our diet pull some of
the weight, like the not-bothering-
to-make-vitamin C thing— let the
fruit do it. Using plants
as a crutch may well have
relieved the pressure for further evolutionary
development of our own defenses, meaning we’ve
become dependent on getting lots of
plant foods in our diet, and when
we don’t, we may suffer adverse
health consequences. Even during
the stone age this may not have
been a problem. Only in recent history did we start giving up
on whole plant foods. Even modern-day paleo
and low carb advocates may be eating
more vegetables than those on
standard western diets. There’s this perception that
low carbers are chowing down on the three B’s:
beef, bacon, and butter, but that’s just
a small minority. What they are eating
more of is salad. The #1 thing an internet
low carb community said they were eating more of
was vegetables—great! If people want to cut
their carb intake by swapping junk
food for vegetables, that’s not
the problem. The concern is the shift
to animal sourced foods. Greater adherence
to a low carb diet high in animal sources
of fat and protein was associated with
higher mortality for example, after
a heart attack, meaning they cut
their lives short. If there’s one takeaway from
our studies of ancestral diets, perhaps it’s that diets
based largely on plant foods promote health
and longevity.