Assignments

Q: Is the Paleo diet our natural diet?

A: Some people claim that the cause of our so-called “diseases of civilization” that are diet related, such as diabetes or high blood pressure, is that our diets have changed radically since the time that hu- man beings evolved hundreds of thou- sands of years ago. If we could go back to the way we were eating before, then we would be much healthier, they say.

It sounds pretty reasonable that if human beings evolved living a certain way and eating certain foods, and if we suddenly and rapidly change from those circumstances, there’s a risk of eating foods that are not necessarily the healthi- est for us.

This idea is supported by looking at modern foraging peoples, who don’t eat Western diets and who certainly don’t seem to suffer as much from conditions like diabetes or hypertension. So, superfi- cially, a Paleo diet makes a lot of sense.

Q: But not when you look deeper?

A: Right. The problem is that it’s really a fantasy to try to construct what early humans were eating.

First of all, what do you mean by early humans? The word “Paleo” doesn’t mean much from a scientific perspective.

Are you talking about the ancestors of the genus Homo, such as Australopithecus? Are you talking about other members of the genus Homo, like Homo erectus? Or do you mean humans in Africa before they migrated out of that continent? Or is it after they left Africa? Or are we talk- ing about people who were living the way that contemporary hunter-gatherers

do—people who forage and hunt but don’t use agriculture?

Q: What difference would that make?

A: Because so far as we can understand, the diets of all these different early hu- mans were really different. What people were eating 10,000 years ago at the dawn of agriculture, for instance, was doubt- less not what people were eating 100,000 years before that.

Q: Didn’t their diets also depend on where they were living?

A: Yes. Picking a specific place or time to say, “Oh yes, we should be eating like those people,” doesn’t make sense. Is seafood okay on a Paleo diet? I suppose it depends on whether you think Paleo people were living on the northwest coast of North America, or whether you think they were in central Africa, in which case

I don’t think there were a lot of shrimp available there.

Take the ancestors of the Inuit First Americans living in the Arctic. They get a lot of attention from Paleo enthusiasts because they relied on meat and seafood for food since so few edible plants grow up there. But the fact that nothing grows there just means that people can adapt to living without a lot of plant food. It doesn’t mean that they should live that way if they have a choice.

Q: The Paleo diet seems to assume that we’ve stopped evolving. Have we?

A: No. It’s clear that we are not the same as our Paleo ancestors. We’ve changed radically in some ways, like our resistance to diseases such as malaria, and not so radically in others, like the structure of our spines.

We didn’t evolve, evolve, evolve to a certain point and then go, “Phew! Done with that! We’re now perfectly adapted to our environment, and we can eat the same diet from now on. Then dang! Somebody developed agriculture, which was a mistake, and now we’re in trouble.”

There just wasn’t an ideal time and ideal diet from which we are now deviat- ing.

Q: What’s an example of how humans continue to change?

A: People say that humans are the only mammals that continue to drink milk past weaning, which is absolutely true. Some of them then conclude that it’s un- natural for mammals to do this, and that it’s therefore much healthier for us to not consume dairy foods.

Well, the fact is that a great number

The Paleo Solution. Everyday Practical Paleo. Paleo Comfort Foods. Paleo Slow Cooking. The Paleo Diet for Athletes. Paleo Desserts.

Dozens of books tout the wonders of the “original human diet.” But how certain

are we that there was an original diet? And if there was, exactly what did it

include? More importantly: Did cavewomen and cavemen really eat dessert?

Marlene Zuk is professor of ecol- ogy, evolution, and behavior at the University of Minnesota and author of the new

book Paleofantasy: What Evolution Really Tells Us about Sex, Diet, and How We Live (W. W. Norton & Company). Zuk spoke to Nutrition Action’s David Schardt by phone from St. Paul.

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With little or no evidence, the book prom- ises to help people with Alzheimer’s, Par- kinson’s, cancer, multiple sclerosis, chronic fatigue, autoimmune conditions, and more.

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Pondering PALEO

of human beings have evolved an abil- ity to keep digesting the lactose in milk throughout their lifetimes. That change happened just over the last 5,000 to 7,000 years, which is really quick from the standpoint of evolutionary change.

So saying that we should eat only what our ancestors ate before this ge- netic change happened makes as much sense as saying that we should eat only what our mammalian ancestors ate be- fore they came down from the trees and started living on the ground.

That’s not to say that there aren’t some people who have trouble digesting milk, but that’s different from saying that all people, all the time, would be better off without it.

Q: The Paleo diet shuns grains. Did early humans ever eat them?

A: The absence of starchy foods on a Paleo diet is really interesting because it’s based on a fantasy of what our an- cestors ate. Over the last 10 years, after

Paleo diets started to become popular, scientists have discovered traces of seeds and grains on the teeth of fossilized early humans. They’ve also found remnants of grains on stone cooking tools.

It’s looking like some early humans not only ate grain, but they also were grind- ing it into a crude flour and cooking that into a primitive form of pita bread.

There’s also good evidence now for a continued evolution in amylase genes. Amylase is an enzyme in our saliva and our small intestine that breaks down starches so we can absorb them. If you look at populations today that eat a lot of starch, they’ve evolved more cop- ies of amylase genes than populations that don’t eat much starch. Extra copies make the digestion of starchy foods even easier.

The moral is that you’re really on shaky ground every time you try to set up a “this is how it was and that’s how we should be” standard. We’re always revising our ideas of what early humans were like, and that is a worthwhile endeavor. But we shouldn’t do it to find what we’re supposed to emulate.

Q: We’re now learning that our microbiome can affect our health.

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Our ancestors may have eaten lean meat, but the recipes in many Paleo books call for ground beef and pork, lamb, sausage, bacon, and other fatty meats.

Paleo in Comparison “If it wasn’t on a caveman’s menu, it shouldn’t be on yours.” That’s the basic premise of a Paleo diet.

Translation: plenty of meat, poultry, eggs, seafood, vegetables, fruit, honey, and nuts, but no grains (breads, cereals, pasta, rice, oatmeal, cookies, pastries, cakes, muffins, etc.), beans, dairy foods, refined sugars, caffeine, or alcohol.

What does a Paleo diet look like? Most books give no specifics (like “eat 20 ounces of meat, poultry, or seafood and 12 cups of vegetables and fruit a day”). But we did find this sample day’s worth of food (2,200 calories) for a young woman in The Paleo Solution, by Robb Wolf (Victory Bell Publishing, 2010), one of the best-selling Paleo books on amazon.com:

Breakfast

Broiled salmon (12 oz.) Cantaloupe (1¾ cups)

Lunch

Broiled lean pork loin (3 oz.) Salad—lettuce (1½ cups), carrots (½ cup), cucumbers (¾ cup), tomatoes (11⁄3 cups), walnuts (5 halves), lemon juice (2 Tbs.)

Dinner

Lean sirloin tip roast (8 oz.) Steamed broccoli (3 cups) Salad—mixed greens (3 cups), tomato (¾ cup), avocado (½ cup), almonds (35), onions (¼ cup), lemon juice (2 Tbs.) Strawberries (1 cup) for dessert

Snacks

Orange (½) Carrots (¾ cup) Celery (1 cup)

How healthy is the Paleo diet (assuming this sample is typical)? On the plus side, it’s rich in fruits, vegetables, fiber, vitamins, potas- sium, and magnesium. It also has no refined sugar or white flour and it’s low in sodium (unless you pour on the sea salt).

But the diet has some drawbacks. Red meat—and especially processed meats (like sausage, ham, and bacon)—may raise the risk of colorectal cancer. The red meat (and the coconut oil and butter in some books) could be high in saturated fat. (Paleo books recom- mend lean meats, but the meats in their recipes often aren’t.) The diet is also high in cholesterol and low in calcium and vitamin D.

A safer bet: the diets used in the OmniHeart study, which lower blood pressure, LDL (“bad”) cholesterol, and triglycerides. They’re similar to the Paleo diet in that they have far more fruits and veg- etables and far fewer grains and sweets than the average American diet. But the OmniHeart diets limit red meats, saturated fat, and cholesterol. (See Nutrition Action, Oct. 2009, cover story.)

NUMBER OF DAILY SERVINGS*

Food (serving size) Paleo Diet OmniHeart

Meat, poultry, fish (¼ lb.) 8 4

Vegetables, fruit (½ cup) 27 9

Nuts (¼ cup) 1½ 1

Grains (½ cup or 1 slice bread) 0 4

Low-fat dairy (1 cup milk) 0 2

Oil, mayo (1 Tbs.) 0 4

Sweets (1 small cookie) 0 2

* We converted Paleo servings into OmniHeart servings for comparison.

Source: JAMA 294: 2455, 2005.

Has our microbiome changed?

A: We are quite different from our ancestors in our microbiome, the billions of microorganisms that reside on and in us that we didn’t know existed 25 years ago when the Paleo movement began.

Think of yourself as a coat hanger of humanity on which are draped this huge number of microbial cells. The microbiome is a part of who we are and it’s essential for our normal functioning. But it differs from person to person, from place to place, and probably over time.

We don’t know how much or in what ways our microbiome has changed from that of our ancestors, although we do have a hint that there have been enormous changes. Some of this probably has to do with changes in the atmo- sphere or diet, not evolu- tion. It’s more evidence that we are not who our ancestors were.

Q: Does Paleo food exist today?

A: Not really. Even if you wanted to try to eat what people were eating a long time ago, the majority of those foods are simply not available. Early humans were not eat- ing plants or animals that resembled very closely the plants or animals that we eat today.

Human beings have been influencing the foods they eat ever since there were people. For example, the ancestors of apples were nasty, horrible, little tiny bitter things that, really, why would one eat them?

The ancestor of corn that was used by peoples in the Americas for quite a long time was called teosinte. It looked like the head of a grass seed, which it basically was, and nothing like what people eat now.

The meat in the supermarket, even grass-fed beef, has also been modified from its ancestors by breeding. People un-

derestimate the degree to which human beings have affected everything in their environment.

Q: Don’t some people say that they feel healthier eating a Paleo diet?

A: I’m not arguing with people who say, “I started eating this way and I feel great.” More power to you. But it’s also perfectly possible that people who eat in a variety of other ways, as long as they’re not sub- sisting on Coke and Cheetos, would be healthy as well.

The way to find that out is not to look more closely at what early people were supposedly eating. It’s to gather evidence about who we are now.

Q: S. Boyd Eaton, the Emory University professor who co-wrote The Paleolith- ic Prescription in 1988, which helped start the Paleo movement, says that he eats a “soft version” of the Paleolithic diet, which includes whole grains, low- fat dairy foods, and wine. Those are foods that are usually forbidden on a strict Paleo diet.

A: That’s exactly the point. You can call the diet Paleo, but let’s take as an inspira- tion what we think was a healthy way to live and then figure out which aspects of the diet make the most sense, relying on science, not on an idealized version of our earlier selves, for the answers.

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Shed Pounds on Paleo? No Evidence Earlier this year, US News & World Report asked a panel of 22 diet experts to rank 28 popular diets. The criteria: Were they effective for short-term or long-term weight reduction? Were they easy to fol- low? Were they safe and nutritionally balanced?

Topping the list was the DASH diet. (A variation of DASH called OmniHeart is the diet recommended by most health experts. See Nutrition Action, Oct. 2009, cover story.)

Dead last? The Paleo diet, which the panel noted was supported by studies that were “few, small, and short.”

Loren Cordain, an exercise physiologist at Colorado State University and author of The Paleo Answer: 7 Days to Lose Weight, Feel Great, Stay Young, disputed the panel’s conclusions.

“Five studies, including four since 2007, have tested ancestral—or Paleo—diets and have found them superior to Mediterranean diets, diabetic diets and typical Western diets in regards to weight loss, cardiovascular disease risk factors, and risk factors for type 2 diabetes,” he wrote to the magazine.

But all five studies cited by Cordain were just as US News said: small and short term. Three of the five didn’t compare people who were randomly assigned to either the Paleo diet or another diet.1-3 Without that “control group” following another diet, researchers couldn’t tell if people lost weight because they were on a particular diet or simply because they were participating in a study.

In one of the two studies that did compare Paleo with other diets, Swedish researchers randomly as- signed 29 middle-aged or older men with heart dis- ease and pre-diabetes or type 2 diabetes to an “Old Stone Age” diet (lean meat, fish, fruits, vegetables, root vegetables, eggs, nuts) or to a “Mediterranean” diet (whole grains, low-fat dairy foods, vegetables, fruits, fish, oils, margarine).4

After 12 weeks, the Paleo eaters had lost no more weight than those on the Mediterranean diet. How- ever, the Paleo group did have lower blood sugar levels after a glucose tolerance test, which measures how well insulin controls blood sugar.

Two years later, the same researchers looked at 13 men and women in their 60s with type 2 diabetes. The volunteers were told to eat a Paleo diet for three months and then a standard diet for people with diabetes for three months, or vice versa. The Paleo diet had more fruits, vegetables, lean meat, fish, nuts, and eggs, and no grains, dairy, beans, refined fats, sugar, candy, soft drinks, or beer.5

They ended up eating 300 fewer calories a day on the Paleo diet, which may explain why they lost seven more pounds during those three months. And their triglycerides were lower. But there were no differenc- es in blood sugar levels after a glucose tolerance test.

The bigger question: What happens over the long run? At least three trials have compared diets that were either high or low in protein, carbohydrates, or fat—such as Atkins, Ornish, Weight Watchers, and The Zone—on a total of more than 1,200 people.6-8

After one or two years, none of the diets out- shined the others. What mattered most was whether people stuck to them. (The more extreme diets—like the high-protein Atkins and the low-fat Ornish—were the hardest to stay on.)

The bottom line: There’s no good evidence that the Paleo diet will make those extra pounds vanish.

1 Diabetes 33: 596, 1984. 2 Eur. J. Clin. Nutr. 62: 682, 2008. 3 Eur. J. Clin. Nutr. 63: 947, 2009. 4 Diabetologia 50: 1795, 2007. 5 Cardiovasc. Diabetol. 8: 35, 2009. 6 JAMA 293: 43, 2005. 7 N. Engl. J. Med. 360: 859, 2009. 8 Ann. Intern. Med. 153: 147, 2010.