I imagine most readers of this blog would expect a group of subjects to do better on a Paleolithic diet as compared to a standard American diet, but there are few studies actually making the comparison. One was posted yesterday in the Advance-0nline-Publication section of the European Journal of Clinical Nutrition that shows subjects following a Paleolithic diet made major metabolic changes, and made them rapidly.
Before we get into the study, let’s make sure we’re all on the same page when we discuss the Paleolithic diet. We we say Paleolithic diet, what are we really talking about?
The Paleolithic era refers to that period of history of the genus Homo, which began more than 2 million years ago and ran until the Neolithic period started circa 10,000 years ago. The Neolithic era dates to the time when early man set down roots both literally and figuratively when he started to cultivate plants for food and domesticate animals. The Paleolithic era ends and the Neolithic era begins with the advent of agriculture.
So what did Paleolithic man eat? We don’t know precisely because Paleolithic man didn’t leave any written records, menus, cookbooks, etc. The only records Paleolithic man left are the cave paintings, of which Lascaux in France is the most famous. Virtually all of these paintings feature animals prominently, which would lead one to believe that animals figured greatly in the lives of Paleolithic people. Since they didn’t domesticate these animals, and since it seems unlikely that they kept zoos, the most obvious reason these early people focused so much artistic effort on these animals is that they ate them. Carbon-13 isotope studies bear out that idea as the same carbon isotopes found in grass are also found heavily concentrated in the bones of Paleolithic man and other known carnivores, which leads to one of two conclusions: either Paleolithic man spent his days grazing or he ate animals that grazed. I would opt for the latter interpretation.
Keep this idea of Paleolithic man as a meat eater along with the idea of the cave pictures in your mind. We’ll return to them later, but first, let’s look at this study.
Nine healthy, sedentary, non-obese subjects (6 men; 3 women) over the age of 18 recruited from the San Francisco Bay area completed the study. These subjects had their starting diets analyzed – all were on their own version of the standard American diet – and a battery of tests done on them to evaluate multiple metabolic parameters.
Once the beginning data was in hand, the researchers started the subjects on a ramp up to the full Paleolithic diet by giving them daily increases of fiber and potassium.
For the intervention phase, beginning day 1, for adaptation purposes, a series of 1-day cycle diets with gradually increasing levels of potassium and fiber were developed by the research dietitians. This was to allow the subjects’ intestinal tract and potassium handling systems to adjust to the markedly higher dietary content of fiber and potassium. ‘Ramp 1′ diet was given for 1 day, ‘Ramp 2′ diet for 3 days, ‘Ramp 3′ diet for 3 days and finally the ‘Paleo diet’ for the remainder of the study.
Once ramped up, the subjects went on the full Paleo diet for 10 days. An interesting twist to this study was that the subjects were monitored carefully for any signs of weight loss over the course of the study, and any subjects losing even small amounts of weight were encouraged to eat more of the Paleo foods in an effort to maintain their starting weights. Since weight loss itself can bring about metabolic changes, the researchers wanted to make sure that any changes came about as a result of the diet composition and not as a side effect of weight loss.
What did they eat?
Meat, fish, poultry, eggs, fruits, vegetables, tree nuts, canola oil, mayonnaise and honey were included in the Ramp and Paleo phases of the diet. We excluded dairy products, legumes, cereals, grains, potatoes and products containing potassium chloride (some foods, such as mayonnaise, carrot juice and domestic meat were not consumed by hunter-gatherers, but contain the general nutritional characteristics of preagricultural foods).
Hmmm. More about which later. For now, here is a layout of the specific foods the subjects ate during the ramp and the full Paleo diet.
The macronutrient composition of the regular diets of these subjects was 18% protein, 44 % carbohydrate and 38% fat. The Paleo diet was 30% protein, 38% carbohydrate and 32% fat, mostly unsaturated, as the authors were quick to point out.
After the 7 day ramp period and the 10 days of Paleo dieting, subjects experienced large changes in most parameters measured. Lipid changes are shown in the table below.
As you can see, there were significant decreases in triglycerides, total and LDL-cholesterol with no change in HDL-cholesterol.
The body of the paper reports an insignificant decrease in blood sugar after the Paleo diet, but the units listed in the paper are incorrect, which is one of the hazards of dealing with a pre-publication paper. All the kinks haven’t been worked out.
Fasting insulin levels plummeted by more than two thirds in (11.5 to 3.6 µU/ml) and the total area under the insulin curve was lowered by almost half. What these figures tell us is that the diet made these subjects much, much more sensitive to their own insulin. In other words, they required substantially less insulin to keep their blood sugars in the normal range. Since they were producing less insulin, they had less circulating insulin, which meant less fat storage, less arterial stiffening and less of all the things that too much insulin causes.
Along with the improvements in lipids and insulin sensitivity, the subjects experienced a significant drop in diastolic blood pressure and a decrease in mean arterial pressure. These improvements likely occurred in part because these subjects had substantially increased brachial artery diameter, a measure of arterial distensibility. There arteries had become less stiff and more pliable over a mere 17 days of dietary change.
Urinary potassium loss increased, indicating an increased potassium intake by the subjects. And urinary calcium excretion decreased.
Another interesting aspect of this study is that these findings were pretty much across the board. Instead of a couple of hyper responders raising the average, either all nine or in a couple of cases, eight of the nine subjects demonstrated pretty much the same changes, indicating
consistently improved metabolic and physiological status with respect to circulatory, carbohydrate and lipid metabolism/physiology.
The authors of this paper found
in a small group of sedentary, slightly overweight, but not obese adult humans, that switching from their usual diet to a paleolithic-type diet, which contained no cereal grains, dairy [or] legumes, resulted, after only a short period of time [17 days] and without weight loss or increase in activity levels
significant positive changes in all the parameters discussed above.
I was fascinated by this study because the changes were so rapid, but I was a little put off because it could have been so much better. I mean why didn’t they test a real Paleolithic diet? Probably because of nutritional correctness, i.e., fear of saturated fat.
During Paleolithic times, man primarily subsisted by hunting. The preferred food was large game animals, and Paleolithic man, a skilled hunter, wiped most of them out. And not just the large grazing animals. Paleolithic man completely decimated the Cave bear. As you can see from the photo of my Cave bear skull below (from a slide I use in presentations), these were enormous animals that didn’t go down easily. Cave bear, like all bears, had high levels of body fat, which must have been highly desired because these ferocious animals were hunted to extinction about 15,000 years ago by people wielding little more than pointed sticks. I would have to value fat a whole lot more than I do to tackle one of these guys. The largest bears that I could find the fatty acid composition for were polar bears, which should be appropriate since cave bear lived in northern latitudes. Polar bears have on average 30 percent saturated fat, 50 percent monounsaturated fat and 15 percent polyunsaturated fat. (I know these figures don’t add up to 100 percent, but they are the figures as presented in the article.)
The majority of the large animals that roamed the world are gone thanks to the depredations of Paleolithic man. If you ever get the chance to go to the American Museum of Natural History in New York, take a stroll through the many large halls filled with the enormous skeletons of these animals that used to roam what is now the United States. Experts estimate that it took Paleolithic man only about a thousand years to range from northern North America were he crossed the Bering strait to the southern tip of South America wiping out all the large game that existed at the time.
These large mammals that Paleolithic man decimated are now only present in skeletal form so we don’t know for sure what their fatty acid composition was. But we do know that of those left, the larger the animals, the larger the percent body fat. And the larger the percent body fat, the greater the percentage of saturated fat. Given those two facts, one has to conclude that Paleolithic man consumed a large percentage of his energy as saturated fat. We can’t look at the fat content of deer, for example, and use that to estimate the saturated-fat content of the Paleolithic diet. Deer, as we know them today, were tiny animals as compared to those Paleo man typically dined on.
If you look at the fatty acid breakdown of the horse, a large animal (not grain fed) that we are all familiar with that is comparable in size to many of the animals Paleolithic man hunted to extinction, you find a large proportion of saturated fats. Horse fat is about 36 percent saturated fat, 34 percent monounsaturated fat, and the rest polyunsaturated fat. Even rabbits carry over 40 percent of their fat as saturated fat, but rabbits have much less fat per weight than the larger animals.
It seems pretty obvious that Paleolithic man would have eaten considerable saturated fat. Which begs the question: Why always cut the saturated fat in experimental diets testing the hypothesis that the Paleolithic diet is more healthful?
I don’t know the answer for sure, but I expect that it’s due to the nutritional equivalent of political correctness, which I call nutritional correctness.
Researchers are simply afraid to imply that saturated fats might actually be harmless, so they go through all kinds of contortions to present their data in such a way that it couldn’t possibly present saturated fats in a positive light. And much good research and reporting has suffered as a consequence.
A case in point is a otherwise wonderful book published 20+ years ago titled The Paleolithic Prescription. This fascinating book goes into great detail describing the physical exploits of our ancient ancestors based in large part of reports by European explorers encountering ‘primitive’ peoples untouched by the forces of ‘civilization.’ The authors, based on the anthropological literature, describe the size of our Paleolithic forebears as being similar to our own, but their strength was significantly greater:
These people were strong – stronger by all estimates than most agricultural and industrial people (including ourselves) who lived after them. Skeletal remains reflect strength and muscularity: the size of joints and the sites where muscles are inserted into bones indicate both the mass of the muscles and the magnitude of the force they were able to exert. Average Cro-Magnons, for example, were apparently as strong as today’s superior male and female athletes. Strange as it may seem, Cro-Magnons and other hunters and gatherers may have worked fewer hours per week than did the agriculturalists who followed, yet they were significantly more robust.
Think about this last sentence for a minute. Strong, robust Cro-Magnons who settled into a life of agriculture circa 10,000 years ago, and who worked harder than their pastoral predecessors, showed a decline in strength and muscle mass. Why? What The Paleolithic Prescription says about energy expended is true. The skeletal remains of agriculturalists show much more arthritic changes and incidence of joint wear implying much more regular physical activity than hunters. So why did agriculturalists develop less muscle mass and strength? Could it be because of a switch from diets high in fat and protein to diets low in fat and protein and high in carbohydrates? Makes sense to me. Same genetic material, greater exercise, different diet, yet weaker and less robust.
Getting back to my original point about this book, the authors presented a mass of data showing our Paleolithic ancestors to be more robust, healthier and able to routinely perform feats of strength that are almost unbelievable to us today. And they dwelt on the massive amount of hunting that sustained these ancient peoples. Then, when it came time to apply these dietary lessons to people of today, the authors tried to shoehorn their findings in a nutritionally correct regimen that followed the low-fat diet precepts that academicians are so attached to. It’s really a shame because this could have been a wonderful book. It’s still well worth reading, but simply ignore the dietary advice.
It would have been great had the authors of the paper above used a real Paleolithic diet for their study instead of an imaginary Paleolithic diet that conformed to the tenets of nutritional correctness.
Based on my own experience with thousands of patients, I can predict what the findings would have been. Lipid parameters would have been improved, but with LDL staying about the same or maybe going up a little. HDL would have gone up significantly. Triglycerides would have fallen maybe more. The all-important triglyceride/HDL ratio would have plummeted much more than with the faux Paleo diet. Fasting insulin would have dropped like a rock and the area under the insulin curve would have fallen at least as much, if not further. Blood pressure would have decreased and all the measures of vascular pliability would have improved. All in all, my prediction is that the outcome of the study would have been better than the outcome of the study as it currently exists.
The Paleolithic diet data indicates that early man ate more saturated fat than he did carbohydrates. And he was molded by the processes of natural selection to thrive on such a diet. When he bolted from that meat-based diet, as he did when he settled in to life as an agriculturalist, he paid dearly for it with a devolution in health. Since the evidence is so obvious that a diet higher in saturated fat worked wonders for Paleolithic man, it seems like some academicians somewhere would ranger up and test such a diet. But it appears that the pox on saturated fat is so virulent that no one wants to risk it.
If such a study were done and the results tally with what I’m positive the results would be, the authors would find themselves in the untenable position of having to at least tacitly imply that saturated fats aren’t harmful. And that could ruin an academic career. No more invitations to present at meetings. Expulsion from the club. People tsk tsking behind their hands. It just couldn’t be done.