Poking holes in 'paleo'

Take ‘cave man’ diet claims with grain of salt, scientists say

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 human 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 says, 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. Modern humans typically produce their offspring decades before developing the diseases that kill or disable adults -- heart disease and strokes, for example.

If the people who lived before agriculture were healthier than modern people, 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."

GOOD OLD DAYS

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 at St. Paul and author of Paleofantasy: What Evolution Really Tells Us About Sex, Diet, and How We Live.

She says, "There's always been this thread of people wanting to live what they perceive is a more

ActiveStyle on 03/02/2015

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