The Paleo Diet Belongs in Caves: What You Really Need to Know About Diets

picture of Harry KellerBy Harry Keller
Editor, Science Education

Diets provide a great opportunity to exercise critical thinking. Pick any diet and pick it apart. Do this as a mental exercise or, if you teach, with your classes. Chances are that many of your students’ parents have dieted or are dieting. In this article, I am picking on the currently trendy Paleo diet.

The Paleo diet persists. I have a strange theory about diets. The first part is that people don’t like to diet. They like to eat whatever they choose. I suspect that this is especially true of libertarians. The second part is that many people see their food as a health problem and would like to change their eating patterns.

Many years ago, the Grapefruit Diet was very popular. This was great for people who loved grapefruit but not so much for those who found them too sour or too messy. Then, there was the problem that grapefruits are like the proverbial Chinese dinner that left you hungry shortly after finishing it. “Have another piece of grapefruit” just doesn’t work for most people.

Skeleton and restoration model of Neanderthal (La Ferrassie 1). Exhibit in the National Museum of Nature and Science, Tokyo, Japan.

Skeleton and restoration model of Neanderthal (La Ferrassie 1). Exhibit in the National Museum of Nature and Science, Tokyo, Japan.

Anyway, my theory is that diets are successful not if they work but rather when they cater to people’s desires. If you could get away with an ice cream diet, you’d have the world doing it because “everyone likes ice cream.” I haven’t yet seen a broccoli diet even though it would probably work better than grapefruit. 

There have been diets that eliminate carbohydrates or fats. There have been diets that emphasize protein intake. (These are dangerous because they put an extra load on your kidneys from all of the extra nitrogen and tend to load you with more saturated fats.)

Where does the Paleo diet fit in and what is it?

First of all, what does the name mean? It comes from the Paleolithic era. The word itself has a prefix of “paleo” meaning old and a root of “lithos” meaning stone. It doesn’t take too much noodling to figure out that Paleolithic refers to the Old Stone Age. Turns out that the Old Stone Age is really old. It began over two million years ago, maybe as much as 2.6 million. And it’s also comparatively young, ending around 10,000 years ago as the Mesolithic (Middle Stone Age) era began.

At the distant time of 2.6 million years ago, Homo sapiens had not yet appeared. Even fire had yet to be controlled. Regular use of fire began perhaps 400,000 years ago. Modern humans are estimated to appear about 200,000 years ago. The extant species 2.6 million years ago may have been Homo habilis, a tool-using species. Homo erectus appeared later with its earliest fossils being only about 1.6 million years old.

Simplifying, the Paleo diet has you eating meat, fruit, and vegetables but no grains, even whole grains. You avoid any processed foods but are allowed to cook. Grains supposedly were not part of the diets of our early ancestors, including those between 400,000 and 10,000 years ago after fire came to be used. The evidence on this point is not conclusive. People may have been eating grains in some areas as far as we can tell. Legumes also are proscribed. No peas, lentils, or beans are allowed. Even potatoes are eliminated. Nevertheless, eat your fill of eggs and meat, cooked of course.

The lack of fire is crucial to understanding the diet of the Lower Paleolithic Era. The oldest portion is termed “lower” because its sediments are in lower strata than more recent eras. This is the geological “law of superposition.” Newer stuff piles on top of older stuff. This is so obvious that you have to wonder about giving it a special name, but generations of school children must have something to memorize, after all.

The theory behind the Paleo diet is that evolution has been too slow to accommodate the newer forms of foodstuff that we consume today. While I’ll concede that Fritos and Twinkies are certainly of such recent vintage as to make any sort of evolutionary adaptation impossible, it’s necessary to look more deeply and find out what it means to eat as our ancestors did.

If you examine the situation carefully, you’ll find a number of contradictions and uncertainties. For example, the argument that we are evolutionarily suited to some particular set of foods fails because our success as a genus and, later, as a species is due to great adaptability in what we eat and not to some diet imagined for our predecessors. Because of this fact, the actual diet of our ancestors was highly dependent on geography. No specific diet can be attributed to any group without reference to location.

Moreover, the diet changed enormously when fire was tamed. Before fire, everything had to be eaten raw. There’s not much problem with raw fruit, raw leaves, raw nuts, or even raw roots, except that raw roots will not give up all of their nutrition in human stomachs and intestines. The situation for meat is much more severe, however.

Modern observation of chimpanzees shows that although they do capture and eat monkeys from time to time, the pieces of raw meat pass through their digestive systems little altered from when they were swallowed. Raw meat does not provide such a rich source of calories and protein for primates as it does for carnivores — by a large margin. In addition, the game being slaughtered in the Paleolithic was not the cattle standing in feedlots becoming fat and lazy today. These were tough wild animals, and chewing on their leathery muscles would have been quite a chore for hominids with their grinding, instead of slicing, molars.

Fire changed everything. Not only does cooking meat make it possible to obtain much more nutrition from and make it easier to chew, cooking does the same thing to roots. Because the Paleo diet emphasizes meat eating, among other things, it really mimics the Upper Paleolithic Era more closely than the bulk of that era. It’s probable that even in the upper portion of the era, meat was not the primary source of nutrition.

Diets in the earliest Paleolithic would have consisted mainly of fruits and vegetables. The animal products consumed would most likely have been insect grubs and, if near water, aquatic animals that could be caught or pried from rocks and then eaten raw. It’s the earliest version of sashimi. There may have been some eating of carrion, if not too ripe, along with included maggots, probably considered a treat.

This is not my favorite diet. I doubt that it’s yours either. That’s really just fine because the Paleo diet fails to mention that the typical lifespan of our Paleo ancestors was very short. Evolutionary pressures were not disposed toward long life in those early days. Hardening of the arteries and strokes were probably essentially unknown then. Our long-ago ancestors mostly died of other causes long before the diseases of old age that we see today were noticeable.

For this reason, any diet based on the early hominids is meaningless for us. We are interested in longevity, and our distant ancestors were not being evolutionarily selected for long life, for avoidance of diseases of old age. Their diets could be absolutely awful for that purpose and still allow them to produce plenty of offspring.

Another factor is evolution itself. In 2.6 million years, our bodies can evolve to deal with different diets. We see that today in some people being lactose intolerant and others able to drink milk readily. Long ago, our children ceased to produce lactase (the enzyme responsible for making milk sugar, lactose, digestible) after they were weaned. Farming brought about the possibility of animal husbandry and of milking goats, sheep, and cattle. Those able to use this new food source, who did not lose their lactase early on, were able to survive better in hard times and become more successful in reproducing and passing on this gene to their progeny. This all happened relatively recently.

Our digestive systems are at least somewhat different than those of Homo habilis, making choices based on them or even on Homo erectus suspect. If diet has anything to do with health and longevity, then copying these early hominids makes little sense. Really! Do you wish to look like a typical Homo erectus? You’d certainly like to live longer.

How should diets be determined? As a scientist, I choose to use scientific evidence and research to find out how to eat, instead of attempting to infer some million-year-old diet from limited evidence. Doing so is not very easy because of a great many factors. I will assume that we wish to have optimal health and longevity and not to become a weight lifter or body builder or even a marathon runner.

Looking at current evidence, the Paleo diet has one part right. You should minimize your consumption of refined foods such as white sugar and white flour. Both contribute to becoming overweight and eventually diabetic. You should also avoid chemically processed foods such as hydrogenated oils that have been demonstrated to contribute to heart disease. Because a healthy digestive system helps to keep your body healthy, you should eat quite a lot of high-fiber foods. They help to clean out your intestines and to keep you “regular.”

However, the Paleo diet misfires on meat. Red meats should be minimized or even eliminated. Steak for breakfast followed by hamburger lunches, in turn followed by pot roast for dinner, is a recipe for heart disease and cancer. All medical research in recent years concurs. I haven’t seen the research on a diet of fowl and fish yet, but simply considering the problems of excess protein intake suggests that you should eat these in moderation. The same goes for eggs and cheese.

The newest research indicates that chronic tissue inflammation is behind a host of life-shortening diseases and that many factors can cause inflammation, including excessive saturated fatty acids as found in animal products. Even eating excessive calories can result in your own body manufacturing these to its own detriment.

A real Paleo diet would have you eating insect grubs and raw fish in addition to plenty of raw fruits, vegetables, and root vegetables. It might be supplemented occasionally by some meat that has sat out long enough to soften but not become poisonous. Yuck!

I, for one, do not have any desire to return to the caves anymore than I’d like to find myself infested with fleas and lice. We have learned much about how to live healthier and longer lives. Discoveries have added substantially to our lifespans. Penicillin alone added enormously. Early antibiotics are credited with adding eight years to our average lifespan and with saving millions of lives.

People like the Paleo diet because it lets them continue to consume meat at alarming rates not experienced by most of mankind until very recent times. Diets succeed in gaining adherents if they are easy to do and fit in well with a preexisting lifestyle. They fit preconceived ideas of what people like to eat. Eating plenty of meat is something that a great many people aspire to. It’s a sign of success.

If you reduce your consumption of animal products, you will feel better rather rapidly. Do not concern yourself with protein intake. All unprocessed food contains protein. Spinach, to name one, has more protein per calorie than just about any other ordinary food. After all, every living cell has protein, whether plant or animal.

Do not jump into any diet without first looking to see what’s behind it and whether it makes sense logically, not whether it feels good in your gut (pun intended). Don’t try to make extreme changes to your eating habits quickly. For example, eliminate “junk foods” first, and that includes soft drinks that either provide no nutrition (diet sodas) or are flavored sugar water. Next, avoid white flour products as much as possible. After that, your choices depend upon who you are and where you are. I personally prefer a whole-food, plant-based diet, and it works well for me. An Inuit would have problems with it though.

Let’s leave the Paleo diet where it belongs. In caves.

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