Katz, MD: Paleo Diet

[Guest guest]

Fundamentally, I am a proponent of the Paleolithic

diet<http://en.wikipedia.org/wiki/Paleolithic_diet>.

However, much depends on the specifics of the Paleo diet in question. The

designation seems to be somewhat open to interpretation -- and thus the

dietary devilry may reside in the details.

That, in essence, is the punch line for this piece -- and I provide it right

away as a bow to a recent correspondent who reminded me that busy readers

want the take away, right away. I do, however, hope you hang in there for

the rest. Assuming so, let's start this tale at the beginning.

In June of this year, *U.S. News & World Report* published a ranking of

diets <http://health.usnews.com/best-diet> for weight loss and health

promotion. They circulated the contestants to a panel of 22 judges, all with

relevant expertise, who scored each diet in multiple categories. Scores were

tallied and winners declared. The overall winner for weight loss was Weight

Watchers. The Paleo diet fared rather

badly<http://health.usnews.com/best-diet/best-overall-diets>

..

Shortly after the rankings were published, I was contacted by ABC

News<http://abcnews.go.com/Health/caveman-diet-online-support/story?id=13897179>\

and

asked to comment on why the Paleo diet had been scored so poorly and

what I thought about it. My first comment was that I was one of the 22

judges, and that I had *not* scored the Paleo diet poorly. I went on to say

that I considered a true " Paleo diet " -- with an emphasis on eating foods

direct from nature and more plants than animals -- a good idea. I also noted

that the name could mask a host of ills, such as a diet of hamburgers, hot

dogs and bacon.

Apparently, the gist of my comments as quoted by ABC News suggested I was a

general critic of the Paleo diet, and also conveyed my impression that our

ancestors actually ate more plants than animals.

This resulted in correspondence from Loren

Cordain<http://hes.cahs.colostate.edu/faculty_staff/cordain.aspx?sm=a>,

a Professor in the Department of Health and Exercise Science at Colorado

State University, who has published extensively on our Stone Age diet and

its implications. Prof. Cordain's note was very civil, but nonetheless a

chastisement of my excessive emphasis on gathering over hunting, with a cc

to a veritable who's who in paleoanthropology.

I explained to Prof. Cordain, and the others listening in, that I am a

proponent of our true ancestral diet, while dubious about its many modern

variants. The notion -- expressed in much of Prof. Cordain's own work --

that our ancestors ate a lot of meat, has invited modern carnivores to run

up their " Paleo diet " banner and claim to be eating under it.

But they are not, because modern meat is not Stone Age

meat<http://www.ncbi.nlm.nih.gov/pubmed/9104571>.

There were no wild corned beef, salamis or pastramis in the Stone Age, so

processed meat is certainly off the Paleo diet menu. There were no grain-fed

cattle; no pigs fed slop; and no domesticated feed animals raised without

demands on their muscles, either.

The flesh of animals our ancestors ate was generally quite lean, often with

fat content around 10 percent of calories or lower. That fat was far more

unsaturated than the fat in most modern meats as well and even provided some

omega-3.

Prof. Cordain noted that the flesh of grass-fed cattle approximates the

Paleo experience, albeit imperfectly. Game does so even better. I concur --

but how much of this is there in the modern food supply? In my experience,

many people who use the Paleo diet as justification for carnivorous

preferences simply eat more of the kind of meat they tend to find. And

generally, they are not finding antelope.

The issue of animal vs. plant foods remained, however, and I was fully

prepared to simply respond with " mea culpa " (I know when I'm out of my

weight class!), when Dr. S. Boyd Eaton of Emory

University<http://www.ncbi.nlm.nih.gov/pubmed/16441938>was gracious

enough to contribute his views. While many papers examining the

proportion of hunting to gathering are based on averages among modern-day

hunter gatherers in diverse locales, Dr. Eaton has focused on African

populations thought to most closely approximate the original human

experience. Dr. Eaton's work suggests a plant:animal calorie ratio of

1:1<http://www.ncbi.nlm.nih.gov/pubmed/16441938>.

Which, in essence, suggests that any apparent differences I had with Prof.

Cordain were a bit about semantics (volume vs. calories), and a bit about

which data to emphasize. Since plants tend to be energy-dilute and animals

energy-dense, to get a 1:1 calorie ratio means a much greater than 1:1 ratio

of plant food volume to animal food volume. It means quite a lot of

gathering along with the hunting. Mostly plants, in other words, is not

demonstrably wrong. Seemingly in the company of Dr. Eaton, I think my

original assertion defensible.

Of course, the true beginning of a story about our Stone Age diet resides

not with *U.S. News & World Report*, but in the Stone Age. The Paleolithic

era, spanning our use of rough stone implements, extends some 4 million

years into the past.

We may reasonably limit ourselves to the latter half of that span and focus

on the emergence of our Homo

*erectus*<http://en.wikipedia.org/wiki/Homo_erectus>forebears, thought

to be the first highly effective human hunters, roughly 2

million years ago. Our own species, sapiens, arose roughly 300,000 years ago

and our particular subspecies, sapiens sapiens, roughly 30,000 years ago.

Agriculture was not part of the human experience until roughly 12,000 years

ago -- and once it was, nothing was ever the same. But that's a story for

another time.

The Stone Age thus provided several thousand millennia to shape the

adaptations of our genus, and several hundred to shape those of our species.

We carry the genes of the well-adapted, because ancestors not well-suited to

survive, reach adulthood and make babies ... make very poor ancestors. Like

all modern creatures, we are the posterity of pre-modern creatures who " had

the stuff, " and paid it forward.

Among the stuff that mattered was the capacity to extract all necessary fuel

from available foods. This is very easy to understand at the extremes: a

person who required for their survival a nutrient not found on this planet,

would not survive on this planet. A person who could not tolerate a nutrient

essential for survival, such as water, similarly would not survive. While

this is so obvious as to be trivial, it conceals a subtlety: food came

first, physiology came after. There were plants before there were creatures

that could survive by eating plants. There was water before there were

creatures that needed to drink water.

And the same extends to every detail of dietary intake. We are adapted to

survive on protein, carbohydrate and fat because those are the three kinds

of macronutrients this planet provides. We " need " iron and calcium and

essential amino acids and potassium and vitamin C -- because the food supply

available to us on this planet provides them. If it did not, we could not

possibly need them and be here to talk about it. Other creatures that needed

what the planet *did* provide would be here in our place.

It just stands to reason that the diet that shaped our physiology in the

first place would tell us something about the diet for which that physiology

is best suited now. If you find that hard to swallow, consider how we decide

what to feed animals in a zoo. To my knowledge, no clinical trials are

involved in which the lions are tried on a diet of hay and the koalas on a

diet of mackerel. Instead, the animals are all given food approximating what

they were eating in the wild -- their native diet. If this is relevant to

every creature on the planet, how likely is it that it would be irrelevant

to us?

This, then, is the basic argument for the " Paleo diet. " But there is more to

consider. Throughout much of the Stone Age, mean human life expectancy was

all of about 20 years and the life span extended only to about 40. While it

makes sense that our native diet is apt to be good for us, we cannot

conclude that a diet best suited to a two- to four-decade life is just as

good for an eight-decade life.

Our Stone Age ancestors had a high caloric throughput, meaning lots of

calories both out and in every day, due to the high energy demands of Stone

Age survival. Perhaps consuming 4,000 or so calories a day -- and burning

them all -- should be required before the " Paleo diet " label truly pertains.

Dr. Eaton among others suggests that our Paleolithic ancestors consumed as

much as 100 grams of fiber daily<http://www.ncbi.nlm.nih.gov/pubmed/16441938>,

from a variety of plant foods eaten in large enough quantities to fuel that

high energy demand. If 100 grams of fiber a day were required to defend a

Paleo diet claim, there would be very few signed up.

In reality, virtually no one today practices anything close to a true Stone

Age diet and no one at all practices such a diet perfectly. When was the

last time you saw a mammoth?

When the Paleo diet label is used to justify a diet of sausages and bacon

cheeseburgers, the concept has wandered well off the reservation. When used

as guidance away from processed foods and toward a diet based on a variety

of plants, nuts, seeds, eggs, fish and lean meats (preferably wild game), it

is eminently reasonable, and no doubt a vast improvement, over the typical

American diet. Stone Agers did a lot more running than we do and most

certainly did not run on Dunkin'!

We don't know that even a well-practiced Paleo diet is the " best " choice for

health, as compared to a Mediterranean diet, a traditional Asian diet, a

mostly-plant diet, or a well-balanced vegan diet. We do know that a

population of some 7 billion people cannot eat as much meat as a population

in the millions did, without doing the irreparable harm to the planet that

is already far advanced.

That our native diet is relevant to our health seems little less than

self-evident. That we can't get back to the Stone Age from here is equally

so. Exactly how we apply lessons from the past to our current dietary

practices will decide whether effects on our future health, and that of our

planet, are as hoped- or otherwise. So the details matter; let's chew on

them carefully.

*

*

*Dr. L. Katz; www.davidkatzmd.com*

LINK <http://www.huffingtonpost.com/david-katz-md/paleo-diet_b_889349.html>

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