Introduction to the Paleo Diet
The Paleo Diet roared into being with the appearance of a book by Loren Cordain published in 2002 called “The Paleo Diet”. Its menus appealed to North Americans whose taste buds were already finding satisfaction in high fat, high animal-protein foods and at a time when nutrition recommendations were pushing for fat reduction in our diets. The Paleo way of eating strives to emulate the diet of our ancestors who lived during the Paleolithic Period. How does this translate into the practical business of our daily meals? Eating Paleo means eating anything that could be hunted or gathered during the Paleolithic time period – meats, fish, nuts, eggs, leafy greens, regional vegetables and seeds.
In his book, Loren Cordain advises the following (1);
Eat unlimited lean meats, fish and seafood. Animal protein should be eaten at almost every meal. Animal protein should come from pastured or free-range animals including beef, pork, lamb, rabbit, goat, organ meats, poultry, wild game, fish including shellfish, escargot and eggs (chicken, duck or goose eggs, especially those with enriched omega-3).
Eat unlimited non-starchy vegetables and fruits.
Do not eat potatoes or other starchy tubers, legumes or corn.
Do not eat peanuts (they are legumes).
Avoid dairy, cereal grains, salt, sugar and fruit juices.
These original ideas have been altered over time by those claiming experience and understanding of the subject. According to the website Paleoleap.com, the present Paleo diet is (2);
High in fat. Eat generously of saturated fats such as coconut oil, butter, beef tallow, lard and duck fat (but only if they originate in healthy and well-treated animals). Olive, avocado and macadamia oil are also good fats.
Moderate in animal protein. Focus on protein derived from animals including red meat, poultry, pork, eggs, organ meats, wild-caught fish and shellfish. Fatty cuts are encouraged.
Low to moderate in carbohydrates. Eat lots of fresh or frozen vegetables (not including legumes) either cooked or raw and served with a source of fat.
Low to moderate in fruits and nuts. Eat fruits low in sugar and high in anti-oxidants such as berries. Eat nuts high in omega-3 fats, low in omega-6 fats and low in total polyunsaturated fats such as macadamia nuts.
Other tips include;
Eat grass-fed, pastured animals. Try to eat locally or, if that is not possible, choose lean cuts of meat and add supplemental fat through coconut oil or butter.
Eat organic, local and/or seasonal fruits and vegetables.
Do not eat grains or legumes.
Do not eat vegetable seed oils.
Do not eat vegetable oils that are hydrogenated or partly-hydrogenated. These include margarine, soybean oil, corn oil, peanut oil, canola oil, safflower oil and sunflower oil. Olive oil and avocado oil are fine.
Do not eat sugar or drink fruit juices.
Do not eat dairy (except for butter and perhaps heavy cream). If you can’t go without dairy, choose full-fat and/or fermented dairy.
The Paleolithic Period of human development occurred from 2.6 million to about 11,700 years ago (3). It is reasonable to believe that our nutritional requirements were established during our prehistoric past. The question is, which prehistoric past? And so we encounter the first conundrum of the Paleo Diet. Why focus on the Paleolithic Period, a relatively recent and short interval of time plucked from our lengthy evolution? Human development began well before 40 million years ago when the higher primates first emerged. Human evolution was still underway 15 million years later when our great ape ancestors came into existence (4).
In fact our evolution continues unabated to this day. Consider a couple of relatively recent examples of adaptations to our circumstances. Most mammals, primitive humans included, lose the ability to digest milk after weaning. In other words, they become lactose intolerant. Around 20,000 years ago, as early humans delved into agriculture and cattle were domesticated, people in some societies began to repeatedly drink the milk of the animals they were raising (7). Over many generations, the genes of these people changed, allowing digestion of milk sugar (lactose) and the ability to drink milk well past babyhood and into adulthood without gastro-intestinal discomfort. Conversely people in non-milk-drinking cultures such as those of China, Thailand, the Bantu of West Africa and the Pima Indians in the American southwest remain lactose intolerant (10). The practice of agriculture also brought about an evolutionary decrease in the size of our jaws. As the diet of human beings shifted to less fibrous foods, large, strong jaws for chewing uncooked and tough plant materials and meats were no longer required. Gradually jaw size decreased. This alteration impacts about one in five people of today as they require dental procedures necessary to remove or straighten their crowded teeth (8).
The second enigma of the Paleo Diet is its emphasis on meat and fat. Evidence for ingestion of large amounts of meat by Paleolithic humans has been weak at best and is diminishing under continuing archaeological investigations. The human digestive system of today remains remarkably similar to that of the great apes who have always consumed almost exclusively plants (9). Research is revealing that Paleolithic human beings were also eating primarily plants. Evidence of this is emerging from Paleolithic archaeological sites throughout Europe dating from around 30,000 years ago. These sites contain many artifacts indicating the eating of meat. Stone tools and bone fragments are easily preserved over time and their fossilized existence was what lead archeologists to their first conclusions, that our early ancestors existed mainly on meat. But vegetable matter does not preserve well over time. It was not until the presence of microscopic vegetable fragments were discovered in more recent revisits of Paleolithic sites that the prevailing theories began to change. Re-excavations of these ancient places have unearthed significant numbers of starch grains originating from various wild plants and seeds as well as flour residue on the surfaces of grinding tools (15). Similar finds have been made in South America (20). Even Neanderthals, a now extinct branch of early humans long believed to be purely carnivorous, are now known to have been omnivores (species who obtain their energy and nutrients from both plant- and animal-sourced foods). Studies have shown significant plant matter both in the plaque found on ancient samples of their teeth and in their fossilized feces (17,18).
The second enigma of the Paleo Diet is its emphasis on meat and fat. Evidence for ingestion of large amounts of meat by Paleolithic humans has been weak at best and is diminishing under continuing archaeological investigations. The human digestive system of today remains remarkably similar to that of the great apes who have always consumed almost exclusively plants (9). Research is revealing that Paleolithic human beings were also eating primarily plants. Evidence of this is emerging from Paleolithic archaeological sites throughout Europe dating from around 30,000 years ago. Excavations of the sites have unearthed significant numbers of starch grains originating from various wild plants and seeds as well as flour residue on the surfaces of grinding tools (15). Similar finds have been made in South America (20). Even Neanderthals, a now extinct branch of early humans long believed to be purely carnivorous, are now known to have been omnivores (species who obtain their energy and nutrients from both plant- and animal-sourced foods). Studies have shown significant plant matter both in the plaque found on ancient samples of their teeth and in their fossilized feces (17,18).
Certainly primitive humans did indeed hunt and were sometimes successful. However researchers consider that hunting activities did not result in a major source of food until fairly recently in human history. Although the oldest spear discovered thus far dates from about 400,000 years ago, hunting techniques that could make the activity practical and productive were still hundreds of centuries in the future (21,14). Research shows that the diet of hunter-gatherers existing 40,000 years ago consisted of about 65% plant-derived foods (including fruits, tubers, roots, legumes, nuts, grasses and wild grains) and 35% animal-derived foods (which encompassed whatever they could catch – eggs, insects, snakes, lizards, birds and small and large mammals) (11,12,14). A significant portion of their animal protein intake would likely have come from easier-to-capture prey such as eggs, insects and reptiles or from scavenging meat from carcasses left by other predators. Constant and reliable supply of meat was an unlikely reality until agriculture and animal husbandry began to really flourish around 11,000 years ago (13).
Research started over thirty years ago and continuing today quantifies actual nutrient intakes in Paleolithic humans. Average fiber intake ranged from 70 gm daily in those primitive people who were eating the greatest amounts of meat to 150 gm daily in those eating the most plants. The average Vitamin C intake was between 500 and 600 mg daily and the dietary potassium consumption amounted to 7,000 to 10,000 mg daily. Since meat contains no fiber at all and Vitamin C and potassium are obtained mostly from fruits and vegetables, it can only be concluded that people of the Paleolithic Period were eating large amounts of plant-based foods (5,6,11,12).
An interesting comparison of the human diet of the Paleolithic Period to the modern Paleo Diet was performed by Brenda Davis, RD (Registered Dietician from Canada) (16). She shows that, on a daily basis, a Paleolithic person would be consuming an average of 25 to 35% of their calories from fat, 7.5 to 12% of calories from saturated fat and 480 mg of cholesterol. On the contrary, the modern Paleo diet derives about 53% of its daily calories from fat, 19% of calories from saturated fat and contains 1308 mg of cholesterol. The ratio of omega-6 to omega-3 fats was 2:1 in a true Paleolithic diet and is around 11:1 in a modern Paleo diet. (The ideal omega-6:omega-3 ratio is as close to 1:1 as possible.) (6). There are several reasons for these startling differences. First of all, the modern Paleo diet recommends a meat intake much higher than was likely possible during Paleolithic times. Also the meat of wild animals of the Paleolithic Period provided only about 6 to 16% of calories from fat while today’s domestic animals, grass-fed and grain-fed alike, offer a whopping 40 to 60% of their calories from fat. Lastly, the modern consumption of processed vegetable oils, one of the largest contributors of omega-6 fats to diets of today, accounts for the enormous difference in omega-6 to omega-3 ratios between the two diet patterns (16).
As an fascinating sidebar, the claim that meat was the stimulus for the sudden increase in human brain size in our recent evolution is often used to strengthen support for Paleo diets. Our brains have tripled in size over the last seven million years with the most rapid increase in human gray matter occurring during the last two million years when our brains doubled in size. It is generally accepted that this brain growth is linked to changes in diet during the Paleolithic time period and increases in meat consumption have been suggested to be its major contributor. However a recent review of archaeological, genetic and physiological evidence is debunking this theory. This research argues that it was carbohydrate consumption, especially that of starch, that was actually the critical factor for the accelerated expansion of the human brain. Two major advancements in the human condition spurred it on. The first was the advent of cooking. Raw starches are often poorly digested but cooking destroys their fibrous structure so that they become much more digestible, increasing the amount of energy derived from starchy food. The second factor is the evolutionary change in the amount of the enzyme amylase present in human saliva. Amylase facilitates the breakdown of starches into simple sugars such as glucose and the presence of amylase in saliva kick-starts the digestion of these carbohydrates when food first enters the mouth. Glucose is the most important fuel for human life. This is especially true in the brain which uses up to 60% of the glucose available to the whole body. The saliva of early humans (and most primates) contains only two copies of amylase. Over the last million years, changes in human genes have multiplied the production of salivary amylase to more than six copies, increasing the ability to digest starchy carbohydrates. Cooking and the increase in salivary amylase inevitably increased the availability of glucose to the brain, permitting the major increase in brain size (19).
And so, there is controversy regarding the true diet of Paleolithic human beings although it is now agreed among archaeologists and other scientists that early humans likely ate much less meat than originally believed. Still, the lure of the modern Paleo diet with its high meat and fat content is potent. Unfortunately, striving to eat in these modern times those foods that would have been available to our forebears is practically impossible. The same food sources just do not exist anymore. And even if such a diet was achievable, would it be the best way to eat? Our world today places us in a vastly different situation than that faced by our Paleolithic ancestors. We are blessed with an astounding array of food choices that are easy to procure. We also have the advantage of the wealth of information and evidence gleaned from prolific scientific study to help us make optimal diet selections. We no longer need to eat whatever is easiest to gather or hunt.
All that aside, the Paleo diet has a loyal following with its partakers claiming numerous personal benefits. It is interesting to look at the available scientific research that has been presented to support the Paleo diet eating choice. The next three articles on this website will endeavour to shed some light on this challenging topic.
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