Health and Science : The paleo diet: Should you eat like a caveman?

The problem with modern diets is that they rely too heavily on modern, processed foods. If only we emulated
the eating habits of our paleolithic predecessors, we’d be healthier and less obese. That’s the premise of popular
“paleo” diets.
“We are Stone Agers living in the Space Age,” writes
Loren Cordain in his book “ The Paleo Diet: Lose Weight
and Get Healthy by Eating the Foods You Were Designed
to Eat .” “Nature determined what our bodies needed
thousands of years before civilization developed, before
people started farming and raising domesticated
livestock,” writes Cordain, a professor emeritus at
Colorado State University.
The paleo diet consists of meat from grass-fed animals,
fish, fruit, vegetables, eggs, nuts, seeds and olive oil,
along with plant-based oils such as walnut, flaxseed,
avocado and coconut. The diet forbids grains, cereals,
legumes (such as beans and peanuts), potatoes, salt, dairy
products, processed foods and refined sugars. “The idea is
to try and mimic the food groups that our ancestors ate
before the advent of agriculture,” Cordain says.
Why should we eat like our ancestors did during the
Paleolithic period , which ended about 12,000 years ago?
Because our genes have changed very little in the 300 or
so generations since then, Cordain told me, and they’re
adapted to a world where food was hunted, fished or
gathered from the natural environment. Our bodies
didn’t evolve to run on the refined foods found on
grocery shelves today, he says.
But nor did we evolve to be healthy, says Daniel
Lieberman, a professor of human evolutionary biology at
Harvard University and author of “ The Story of the
Human Body: Evolution, Health, and Disease.” What
drives evolutionary adaptations isn’t health, it’s factors
that affect reproductive fitness, Lieberman says. “Natural
selection really only cares about one thing, and that’s
reproductive success.” Evolution favors traits that allow a
species to produce lots of offspring.
If the people who lived before agriculture were healthier
than us, they rarely lived long enough to reap these
benefits, says Kenneth Sayers, an anthropologist at the
Language Research Center of Georgia State University. It
was unusual for hunter-gatherers to live much beyond
reproductive age, he says, and “it’s hard to be healthy
when you’re dead.”
The paleo diet is built on nostalgia and erroneous notions
of how evolution works, says Marlene Zuk , an
evolutionary biologist at the University of Minnesota in
St. Paul and author of “ Paleofantasy: What Evolution
Really Tells Us About Sex, Diet, and How We Live .”
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She says “there’s always been this thread of people
wanting to live what they perceive is a more natural
lifestyle from the past, whether it’s pre-Industrial
Revolution or pre-agriculture or even the 1950s.”
The idea that the Paleolithic era represents some magical
time in our evolutionary history has no basis in fact, she
says. Evolution is a dynamic process that doesn’t build to
some perfect harmony or endpoint, but instead produces
a mishmash of trade-offs and compromises. As an
example of this, she points to bipedalism , which made
humans more mobile but also makes us prone to back
pain and difficulties giving birth. “It’s not like bipedal
humans should have said, ‘Wait, wait! Stay in the
trees!’ ” she says.
Another problem with the paleo diet is that it makes
unscientific assumptions about what our ancestors ate,
Lieberman says. “There was no one single paleo diet;
there were many,” he says. Our Stone Age relatives lived
in a diverse range of habitats, from tropical regions of
Africa to rain forests, boreal forests and tundra regions,
he says, and their diets varied according to what was
available in these habitats. “There is no one time and
place and habitat to which we’re adapted,” Lieberman
says.
Hominids (humans and our immediate ancestors from the
genuses Ardipithecus, Australopithecus and Homo) are
omnivores capable of living in a wide range of habitats,
eating a wide variety of foods, says Sayers, who recently
co-authored an article in the Quarterly Review of Biology
examining the ecology and diets of human ancestors.
Few health professionals would quibble with paleo diet
recommendations that involve increased physical activity
or the avoidance of highly processed foods, Sayers says.
But to set recommendations about what a modern diet
should consist of based on an estimation of what
paleolithic humans ate overlooks the wide variety of
foods that these ancestors consumed. “We are
‘generalists’ in the strongest sense of the word,” he says.
Some of the advice offered by the paleo diets makes
sense, Lieberman says, even if the stories to explain it
don’t. Few would dispute, for instance, that modern diets
often contain too much sugar and empty calories. But
other pieces of paleo diet advice contradict what we
know about human evolution, he says. For instance, paleo
diets forbid dairy products, but numerous people around
the globe have inherited a genetic mutation that enables
them to metabolize milk as adults. This trait evolved
independently at least seven times, Lieberman says, so
it’s simply wrong to say that humans haven’t evolved to
eat dairy foods.
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Nor is it correct to assert that our paleolithic ancestors’
diets were devoid of grain. “We know that hunter-
gatherers in the Middle East were eating grains,”
Lieberman says, because archaeologists have found
remains of wild barley they were gathering, along with
the mortars and pestles they used to grind this grain into
flour. Not every population ate grains, Lieberman says,
but those who had them available certainly did.
“Whether they were healthy was beside the point,” he
says.
Cordain points to studies — such as one from 2009, that
found that a paleo diet improved glycemic control and
several cardiovascular risk factors among 13 diabetic
patients — as evidence that his paleo diet can improve
health. But whether the diet is superior to other ways of
eating remains a point of debate.
Jessica Larson, a nutritionist and registered dietitian at
the Center for Nutrition Policy and Promotion at the
USDA, cautions, “At this time, there is not enough
research on the paleo diet and its potential impact on
health over time.”