Okay, here is what I've been working on for the past couple of weeks, and this is why I haven't updated the blog. Today, I handed in this paper and we did our presentation, so I will have much more free time coming up. Expect a blog post soon about Thanksgiving and this past weekend's trip to Volterra!
Paleolithic Diet Essay
In recent years, there has been an unprecedented rise in America, and across the world, in the prevalence of chronic disease. Human beings have never been so unhealthy in the history of the species. Cancer rates are on the rise, obesity has seemingly spread like the plague, and what used to be known as “Adult-Onset Diabetes” has now been renamed because an increasing number of children have become afflicted. Despite the recommendations of the United States government, which began telling Americans what to eat in 1977 with Senator George McGovern’s publication of Dietary Goals for the United States, chronic disease rates have continued to rise. The recommendations have changed slightly over the years, but they have consistently urged Americans to eat less fat, especially saturated fat, and to eat foods low in cholesterol like grains, fruits, and vegetables. While the science of nutrition can certainly play an important and effective role in determining a healthy diet, it presents some clear problems as well. For one thing, modern mainstream nutrition has created a number of paradoxes. Maybe the most well-known of these is the French Paradox: the nutrition contradiction whereby the French have some of the lowest heart disease rates on the planet, but they eat at least as much saturated fat as Americans do. Even epidemiological evidence has been contradictory; intervention studies have shown that low-carbohydrate, high-fat diets improve cholesterol levels along with other markers for heart disease. In part due to inconsistencies like these, it has become increasingly more popular in recent years to take an evolutionary view of nutrition, looking to human history for insight into what may be the ideal human diet.
The Paleolithic diet, as it is commonly known today, combines the principles of both evolutionary biology and modern nutritional science. Its foundation lies in the idea that human genes have remained largely unchanged since the Neolithic Revolution, marked by the adoption of agriculture approximately 10,000 years ago, and thus humans are maladapted to consume foods that have since then been introduced into our diet. At first glance, this may sound absurd; surely in 10,000 years humans must have had time to evolve; however, experts disagree. While 10,000 years may seem like a long time, in the context of two and a half million years of human history it looks rather insignificant. Most of the leading researchers in the field, such as Loren Cordain and S. Boyd Eaton, agree that the human genome remains unchanged from hunter-gatherer times. Since diseases of civilization like cancer and heart disease were virtually nonexistent in those days, this theory could have profound implications for the increasing incidence of chronic disease. Says Eaton, “Afflictions of affluence are prompted by dissonance between human genes and our current lifestyles, and the prevalence of these diseases may be greatly reduced or eliminated by readopting the nutritional practices of our ancestors.”
The pre-agricultural diet differed drastically from typical diets in the 21st century. A typical hunter-gatherer diet would consist of wild meat, vegetables, fruit, nuts, and seeds, clearly a stark contrast between the diets of modern civilization. Most apparent, there was no consumption of grains, and also no dairy, both of which are staples of many modern diets. Also of note is the large meat and fish consumption. A typical hunter-gatherer would have consumed 56-65% of his calories from meat and fish. Research shows that vegetable and fruit consumption was much higher than in modern diets, even the most vegetable-rich modern diets. In terms of macronutrient ratios, typical hunter-gatherers would consume 25-30% of calories from protein, 30-35% from carbohydrates, and 40-45% from fat. In contrast, modern Americans consume 15% of calories from protein, 55% from carbohydrates, and 34% from fat. There absolutely exists a dissonance between the diet of our ancestors and the diet of the modern world.
Perhaps the most radical feature of the Paleolithic diet, to us, is the absence of grains. Cereal grains, such as wheat, rice, and corn, have become dietary staples around the world. However, it has not always been this way. Before the Neolithic Revolution, grains were not a staple in any human diet. There is some evidence to show that they were eaten as much as 5,000 years before agriculture, but this was most likely only in food shortage situations. Since wild cereal grains are small, difficult to harvest and poorly digested without grinding and cooking, they simply were not worth the trouble. It wasn’t until the adoption of agriculture that cereal grains became an integral part of the diet. Nutritionally there are plenty of reasons to avoid cereal grains. Grains simply do not contribute many nutrients to the diet. They are high in carbohydrates and they are low in bioavailable nutrients, especially minerals. Because of their fiber and phytate content, the bioavailability of important minerals like iron, zinc, copper, and magnesium contained in cereal grains is especially low. Iron deficiency is the most prevalent nutritional problem in the world today, affecting 2.15 billion people worldwide and being severe enough to cause anemia in another 1.2 billion. Grains also do not contain vitamin C or carotenoids, and they may displace foods that do. Foods high in these compounds are associated with a decreased risk for many common cancers and heart disease. Grains that contain gluten, however, may be the most troublesome. Gluten is a protein that is present in wheat, rye, barley, and oats. Only about 1% of the population suffers from gluten intolerance, an autoimmune disease known as celiac disease, but new research shows that gluten may be harming more than just celiac patients. One recent study headed by Dr. Sandro Drago at the University of Maryland was able to show that gliadin, a component in gluten, “activates zonulin signaling irrespective of the genetic expression of autoimmunity, leading to increased intestinal permeability to macromolecules.” This means that, even in non-celiac people, gluten-containing grains may contribute to what is known as leaky gut syndrome, where intact proteins are able to permeate the intestinal lumen without being broken down. This will elicit an immune response, and could lead to autoimmune conditions. Another recent study by Dr. Kenneth Fine examined stool samples to look for anti-gliadin IgA, which is an antibody produced by the body to combat gliadin. To no surprise, 100% of celiac disease patients tested positive for this antibody. However, 29% of healthy, asymptomatic people also tested positive. The only reason anti-gliadin IgA ends up in your stool is because your body sensed an impending threat – gluten. If gluten poses no threat, the anti-gliadin IgA stays in your gut. A food sensitivity like this one can result in a wide range of symptoms, like joint pain, headaches, skin problems, and more. Clearly, grains like wheat are not benefiting the body if it is perceived as a threat. It should be noted that much of this research on gluten is relatively new, due to recent advances in technology which enhance our ability to measure its effects in the body. As a result, the number of studies demonizing gluten-containing grains is very limited, but this is expected to be a major topic of interest in the coming years. In summation, cereal grains present a whole host of potential problems, have low nutrient content, and they displace other nutrient-dense foods in the diet. The human species lived for millennia without eating grains, and nutritionally there is no need to consume them.
Also absent from the pre-agricultural human diet was dairy, which is also extremely common today. At present, humans are the only species that consumes the milk of another animal and the only species that consumes any milk after weaning; except for perhaps pets whose human owners feed them milk. All mammals are born with the enzyme to digest their mother’s milk, but most lose this ability after weaning. Interestingly, many people today are unable to digest lactose, the sugar in milk. A large portion of Africans and Asians are unable to consume dairy products. While people of European descent generally have no problem with lactose, allergies to casein, one of the proteins in milk, are prevalent. Also, like gluten, many undiagnosed people may be sensitive to casein. Testing for food sensitivities is still a young science, since reliable tests like the LEAP-MRT test have only become available recently, and there isn’t a great deal of scientific data on the subject. Also, since symptoms of food sensitivity may not be seen until days after consumption of the food, it is very difficult to pinpoint the culprit. Anecdotal evidence, though, suggests that casein-sensitivity is not all that uncommon. Nutritionally, the main draw of dairy consumption is its high calcium content. Calcium is a vital mineral in the human body, needed to maintain bone density. It is for this reason that the U.S. Government considers it an important part of a healthy diet. But from a historical perspective, it simply doesn’t make sense to consider it so important when for most of human history humans lived healthy lives without it. Fortunately, there are scientific reasons why you’ll get plenty of calcium from other sources. A study published in the American Journal of Clinical Nutrition in 1990 found that absorption of calcium from green leafy vegetables, specifically kale, is superior to its absorption from dairy products. We could also get our calcium from traditional foods like bone broth, which is made by simmering animal bones in water. This also produces a very highly bioavailable form of calcium, and it provides a great use for leftover bones, which would otherwise simply be discarded. It may be, though, that we don’t necessarily need as much calcium as is currently recommended. The United States has one of the highest intakes of calcium in the world, but paradoxically Americans also have one of the highest rates of osteoporosis. The calcium content of bones is not only dependent on the intake of calcium, but also net calcium balance. When one’s diet consists of too many acidic foods, the body must counter this with its own alkaline stores to maintain equilibrium. It turns out that one of the body’s main alkaline stores is the calcium in bone. So when a person’s diet consists of too many acid-producing foods, i.e. hard cheeses, cereal grains, salted foods, meat, and legumes, the body must pull calcium from the bone to produce an alkalizing counterpart. This calcium is then excreted from the body. In order to avoid this calcium loss, the alkaline source must come from the diet, and the only base-producing foods are fruits and vegetables. There are also studies, like the one done by Jane Kerstetter in 2007, showing that diets that are high in protein like the Paleolithic diet increase intestinal calcium absorption and improve bone balance. Therefore, rather than blindly consuming dairy just for its calcium content, it may be more prudent to balance acid-producing foods like meat with base-producing foods like fruits and vegetables, especially green leafy ones. This will provide plenty of protein to improve calcium absorption and also limit its loss from the bones, thus reducing dietary need. In addition, evidence from the pre-agricultural era shows that healthy hunter-gatherer bones were consistently stronger and thicker than those of today. While conventional wisdom says dairy is an essential food group, scientific evidence and historical evidence both show that it is unnecessary and, in some cases, may be harmful.
Most of the calories, 55-65% typically, in hunter-gatherer diets came from the fat and protein in meat and fish. The consumption of fish depended largely on geographical location. Looking through the lens of modern nutritional science, you would expect a high-meat diet such as this one to induce cardiac arrest. We are constantly told to reduce red meat intake and avoid animal fat. On the contrary, coronary heart disease was virtually nonexistent among hunter-gatherers, and there are several reasons for this.
Firstly, the meat that was eaten by hunter-gatherers prior to agriculture was different than the meat we eat today. While our meat comes from domesticated animals raised by humans, their meat came from wild animals. Wild meat tends to be lower in total fat, and the proportion of saturated fat is lower. Monounsaturated fat, mostly oleic acid, is higher. Oleic acid has been shown in studies to have anti-atherogenic effects, meaning it prevents cardiovascular disease. As for polyunsaturated fats, wild meats are lower in omega-6 fats and higher in omega-3, close to a ratio of 1:1 between the two. Wild-caught fish is even higher in omega-3 fats; farmed fish is too, to a lesser extent. The ratio of these two fats is becoming increasingly recognized in the medical community as a marker for cardiovascular disease. While omega-6’s promote inflammation, omega-3’s are anti-inflammatory. In the modern American diet, there are too many omega-6 fats, which can cause systemic low-level inflammation and can lead to heart disease. A 1:1 ratio is believed to be ideal. In addition, hunter-gatherers ate all parts of the animal, which is less common in today’s world. They ate all the meat, including all the organs, and they probably preferred the fattier parts.
The other reason meat didn’t cause hunter-gatherers heart disease is that meat is not as atherogenic as it is made out to be. A recent 2010 meta-analysis from Harvard took a comprehensive look at the studies that have been published about red meat. In the past, the blanket term “red meat” included beef, pork, lamb, and processed meats like sausage, hot dogs, and bacon. For this study, the researchers were able to separate the data from the unprocessed meat and the processed meat. The results showed no association of beef, pork, and lamb with heart disease or diabetes; the association existed only with processed meats. Of particular interest, the saturated fat content of the two groups was essentially the same, indicating that no association was found between saturated fat and heart disease or diabetes. The researchers concluded that the added chemicals and sodium in processed meats were what contributed to heart disease, not the saturated fat. This study is very significant because it exposes a fundamental flaw in the studies used in the past to demonize red meat and saturated fat. Recently, more and more studies are showing this lack of association. Although wild meat contains less saturated fat than domesticated meat, the most up-to-date estimates of saturated fat intake in hunter-gatherers say they made up 10-15% of total calories. Anything outside of that range is considered to be the exception rather than the rule, and is likely to be discordant with the human genome. So then, the current USDA recommendation to keep calories from saturated fat under 10% may contradict our evolution, and it has an ever-dwindling body of empirical evidence.
It may still be possible in today’s world to eat meat that is similar to what our ancestors ate. A study published in 2002 by Loren Cordain compares the fatty acid profile of wild North American and African ruminants with that of pasture-fed cattle and grain-fed cattle. Results showed that the fats in wild and pasture-fed meats were similar, but both were dissimilar to grain-fed cattle. The lipid composition of wild ruminant tissues may serve as a model for dietary lipid recommendations in treating and preventing chronic disease. Another recent study published in Nutrition Journal assessed the specific fatty acid differences between grass-fed and grain-fed beef. Cattle have evolved over millennia to eat grass, not grains, like they are typically fed today. There was no difference in total saturated fat content, but the type of saturated fatty acids were different between the two. In grass-fed beef, there was a higher proportion of cholesterol-neutral stearic acid and lower proportions of cholesterol-elevating saturated fatty acids like myristic acid and palmitic acid. Results also showed more omega-3 fats and much higher content of conjugated linoleic acid, which may have anti-cancer properties. In addition, grass-fed beef has been shown to contain more precursors for Vitamin A and E, as well as antioxidants such as gluathione and superoxide dismutase. Opting to purchase beef and other meat that was fed its natural diet would be an excellent way to emulate our ancestors, and science shows it may even have cardio-protective effects.
The Paleolithic diet contained large amounts of fruits and vegetables, far exceeding their consumption in modern societies. In fact, typical hunter-gatherers probably ate more than double the amount of fruits and vegetables that Western Europeans eat. The data on fruit and vegetable consumption is indisputable. High consumption of these foods is associated with lower cholesterol, lower risk of coronary heart disease, lower risk of cancer, lower blood pressure, lower risk of diabetes, longer life; the list goes on and on. It is no surprise that our species evolved eating these foods in high quantities. They are high in a wide range of vitamins and vitamin precursors, beneficial phytochemicals, and fiber. Unfortunately, fruits and vegetables are typically replaced in today’s diet by other less nutrient-dense foods like cereal grains. In Paleolithic times, humans consumed most, if not all, of their carbohydrates from fruits and vegetables. Unlike contemporary refined flour and sugar, fruits and vegetables as a whole are more slowly absorbed in the intestines and don’t produce sharp spikes in insulin secretion. Excessively high insulin levels in the body are not ideal; this promotes fat storage and over time can lead to diabetes. There is no debate about the positive health effects of a high fruit and vegetable diet.
To my knowledge, there are no published intervention studies involving the Paleolithic diet, hence no causality can be shown. However, there is a wealth of other evidence supporting this type of diet as a whole. The earliest of this evidence comes from studies of human remains from before and after the adoption of agriculture. Studies show that early farmers paid a price for their new-found livelihood. Jared Diamond assessed these studies in his classic article “The Worst Mistake in the History of the Human Race.” According to Diamond, “Compared to the hunter-gatherers who preceded them, the farmers had a nearly fifty percent increase in enamel defects indicative of malnutrition, a fourfold increase in iron-deficiency anemia, a threefold rise in bone lesions reflecting infectious disease in general, and an increase in degenerative conditions of the spine.” Studies of bones also showed a significant decrease in height after the Neolithic Revolution. Male hunter-gatherers at the end of the ice ages stood about 5’9”, while women were 5’5” on average. By 3000 BCE, the average heights were 5’3” and 5’ for men and women, respectively. Life expectancy took a hit, too. Before agriculture, life expectancy at birth was about 26 years. But in the post-agricultural community it was 19 years. Athletically, pre-agricultural humans may have been far superior to modern humans. In a new book by Peter McAllister called “Manthropology: the Science of Why the Modern Male Is Not the Man He Used to Be”, McAllister says footprint analysis shows that ice age aborigines in Northern Australia could run long distances at the same speed as modern Olympic sprinters. Clearly, the human race became less healthy after the adoption of agriculture.
Another effective way to learn about our ancestral hunter-gatherers is to study modern hunter-gatherers. There are small tribes scattered throughout the world who still live and eat like pre-agricultural humans, and these provide a fantastic opportunity to gain insight into the health of the Paleolithic diet. A 2007 study published by Michael Gurven and Hillard Kaplan did just that. Their research showed that obesity is rare, hypertension rates are low, and cholesterol and triglycerides are low in modern hunter-gatherers. Subsequently, heart attacks and strokes are rare in these populations. They actually live very long lives, considering they don’t use any modern medicine. The average modal age of adult death was found to be 72 years, not far off from the average of 77.9 in the United States today. Unlike modern Americans however, people in these societies remain very active into their seventh decade of life, another likely contributor to their longevity. Causes of death were found to be as follows: 70% of deaths are from illnesses, 20% are from violence and accidents, and only 9% are from degenerative diseases. Today, in modern westernized societies, the majority of deaths are due to cardiovascular disease. This evidence seems to suggest that we would do well to emulate primitive eating habits, however further investigation in the form of intervention studies is needed to establish concrete scientific evidence.
For better or for worse, we are no longer hunter-gatherers. However, our genetic makeup is still that of a Paleolithic hunter-gatherer, a species whose nutritional requirements are optimally adapted to wild meats, fruits and vegetables, not to cereal grains and dairy. The question is, then, how can we eat like our ancestral history requires us to in today’s society? We do not need to emulate hunter-gatherers exactly, but the principles of their diet should be the principles of ours. We can begin by removing cereal grains and dairy from the diet. Forget about the fact that grains are the basis for the food pyramid, along with the idea that “milk does a body good.” Also, avoid vegetable oils like corn and soybean oil; they are highly processed and were not eaten prior to the mid 1900’s, and they’re extremely high in omega-6 content. These foods conflict with our genetic makeup and can cause all sorts of problems. Next, eat animals that ate their natural diet. Most meat produced today is fed grains, which reduces the nutrient and lipid quality of the food. Buy grass-fed beef and lamb, and pastured chickens, eggs, and pork. Avoid farmed-fish, too, and opt for wild fish. Their omega-3 content is far superior. Eat lots of plants, preferably organic. Hunter-gatherers ate more vegetables than any modern civilization, and they didn’t use pesticides or synthetic fertilizer. Try to include meat and vegetables in every meal. Eat plenty of fruit to satisfy your craving for sweets, and when you want a snack, eat nuts and seeds. As for cooking fats, extra virgin olive oil and lard are as close as it comes to being Paleolithic foods, even though they didn’t exist in that form. They are fine in moderation, especially in comparison to the alternatives like corn and soybean oil. Eating a Paleolithic diet in the modern world is not only possible, but it is quite probably the ideal human diet. It would be an excellent diet to adopt for anyone looking to reduce their risk for all diseases of civilization.
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