It is generally accepted that the human genome was selected in adaptation to stone age living circumstances culminating in the appearance of behaviourally modern humans between 100,000 and 50,000 years ago. Since then adaptation has mainly involved cultural modification with various ‘revolutions’. The agricultural revolution approximately 10,000 years ago, the industrial revolution from the late 18th century and the technological revolution in the mid 20th century. However, over the last 50,000 years there have been few generally recognised genetic changes and our genome remains adapted for a paleolithic lifestyle. This discrepancy between our genes and our culture has produced a mismatch that affects our lives, it is responsible for the chronic degenerative diseases that are responsible for most mortality in westernised nations. Differences in reproductive behaviour, sleep patterns, physical activity, microbial interactions, social interactions all play important parts in evolutionary discordance theory. However the most important facet is the change in nutrition, particularly since the agricultural revolution. I believe that the diseases of modern society are an example of natural selection occurring in our population. If you are not lucky enough to be one of the people whose genes haven’t the mutations (for example adult lactose tolerance) to enable them to deal with the modern diet or if you want to gain the best health or performance from the genes you have inherited, I would recommend eating a Paleolithic diet. I have seen this type of diet help people with problems including type 2 diabetes and also in creating stronger, faster better performing athletes. In the rest of this section I’ll cover a brief introduction to the Paleolithic diet, including recipes and we’ll take a look at some other interesting nutrition ideas like intermittent fasting, calorie restricted adequate nutrition (CRAN) diets and review some of the diet books that relate to this topic.
What is the Paleolithic diet?
Generally it is the consumption of wild meat and fish, fruits and vegetables and nuts and seeds. Note the absence of all modern processed foods these tend to be high in refined sugar and oils, processed foods also tend to contain high salt levels put in to make the food taste good but not good for you. The Paleolithic diet is also free of grains and dairy products, staples that have only been regularly consumed since the Neolithic approximately 10,000 years ago.
How did the Paleolithic diet differ from today’s diet?
Glycaemic load – the glycaemic load assesses the blood-glucose raising potential of a food based on both the quality and quantity of carbohydrate. Refined grain and sugar products nearly always maintain much higher glycaemic loads than unprocessed fruits and vegetables. The last twenty years has shown that consistent consumption of high glycaemic load foods can adversely affect metabolism and therefore health. Specifically diseases of insulin resistance referred to as diseases of civilisation (Eaton, Konner, Shostak 1988) they include obesity, coronary heart disease, type 2 diabetes, hypertension and dyslipidemia (elevated serum triacylglycerols; small dense low-density lipoprotein cholesterol; and reduced high-density lipoprotein cholesterol). It has also been speculated that the metabolic syndrome may also extend to other chronic illnesses and conditions that are widely prevalent in western society including myopia, acne, gout, polycystic ovary syndrome, epithelial cell cancers (breast, colon, prostrate), male vertex balding, skin tags, and acanthosis nigricans (Cordain, Eades and Eades, 2003).
Fatty Acid composition – Fats fall into one of 3 categories: saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA), additionally essential PUFA occur in two biologically important families the n-6 PUFA and the n-3 PUFA. Substantial evidence now indicates that for preventing the risk of chronic disease the absolute amount of dietary fat is less important than the type of fat (Institute of Medicine of the National Academies, 2003). Beneficial health promoting fats are MUFA and some PUFA, whereas most SFA and trans fatty acids are detrimental when consumed in excessive quantities. Further the balance of dietary n-6 and n-3 is integral in preventing the risk of chronic disease and promoting health. The modern diet frequently contains excessive saturated and trans fats and has too little n-3 PUFA relative to the n-6 PUFA, this is generally because of the high levels of vegetable fats consumed high in n-6 PUFA but has also been attributed to meat from grain fed cattle which also contains a higher n6/n-3 ratio. In the U.S. the current n-6/n-3 ratio is 10:1, in Paleolithic societies the same ratio has been estimated between 3:1 and 2:1. The last fat I’d like to mention here is hydrogenated fat, invented in 1897 it allowed vegetable oils to become solidified. The hydrogenation process introduced a new trans fatty acid – trans elaidic acid into our diets. This elevates blood cholesterol levels, and leads to an increased risk of cardiovascular disease.
Macronutrient composition – It is currently recommended that we consume approximately 60% of total calories from carbohydrate, 15% from protein and 25% from fat. When these ratios are examined using ethnographic and quantative studies of present day hunter gatherers, protein is generally between 20%-35% energy, at the expense of carbohydrate (22%-40% energy) (Cordain et al. 2000). Because protein has more than three times the thermic effect of either fat or carbohydrate and because it has a greater satiety value than that of fat or carbohydrate increased dietary protein may represent an effective weight loss strategy for the obese. Recent trials have shown that calorie restricted high protein diets have been more effective in promoting and maintaining weight loss than calorie restricted high carbohydrate diets. This shows us that the modern principle of diets i.e. a calorie is a calorie is simply not true. It is what you eat and not how much that is the major influence on body composition, health and performance.
Micronutrient availability – Refined sugars are anti-nutrients they are essentially devoid of any vitamins or minerals, when consumed the total vitamin and mineral density of the diet is reduced. A similar situation exists for vegetable oils except they contain vitamin E & Vitamin K. In the U.S. refined sugars and vegetable oils constitute at least 36.2% of the total energy in a typical diet thus reducing the total vitamin and mineral density of the diet. Lean meat, fish, fruits and vegetables, nuts and seeds contain the highest amounts of micronutrients, additionally wild plant foods known to be consumed by hunter gatherers have higher micronutrient yields than their domesticated counterparts. Displacement of lean meat, fish, fruits and vegetables, nuts and seeds by whole grains and milk has also lowered the total vitamin and mineral density of the modern diet.
Acid / Base Balance – Nearly all foods release either acid or alkaline into the systemic circulation after metabolism. The typical western diet yields a net acid load. As a result normal adults consuming the standard western diet sustain low-grade pathogenic metabolic acidosis that worsens with age (over decades). Virtually all pre-agricultural diets were net alkaline yielding because of the absence of grains and energy dense nutrient poor foods – again because of the displacement of the net alkaline yielding fruits and vegetables. The known health benefits of a net alkaline yielding diet include prevention of osteoporosis, age related muscle wasting, calcium kidney stones, hypertension, exercise induced asthma, as well as the progression of age and disease related chronic renal insufficiency.
Sodium Potassium Ratio – The modern western diet contains approximately 3.3 g/day of sodium compared to 2.6 g/day of potassium. This is due to the high sodium content of many processed foods, the low potassium content of vegetable oils and refined sugars and the displacement of high potassium yielding fruits and vegetables by whole grains and milk. Together the addition of sodium and the removal of potassium caused a 400% decline in the potassium intake while simultaneously increasing sodium intake by 400%. This inversion of the sodium potassium ratio in human diets had no evolutionary precedent and now plays an important part in numerous diseases of civilisation including hypertension, stroke, kidney stones, osteoporosis, gastrointestinal tract cancers, asthma, exercise induced asthma, insomnia, airsickness, high altitude sickness and Meniere’s syndrome.
Fibre content – The fibre content of modern diets is substantially lower than early human diets and also considerably lower than recommended values (25-30 g/day). Refined sugars, vegetable oils and alcohol are devoid of any fibre and compose an average of 48.2% of the energy in a typical U.S. diet. Fresh fruit typically contain twice the fibre of whole grains and non starchy vegetables contain almost 8 times more fibre than whole grains. Again displacement of fibre rich fruit and vegetables by the dietary staples introduced during the agricultural and industrial revolutions was to bring trouble in the form of constipation, bowel cancer, appendicitis, haemorrhoids, deep vein thrombosis, varicose veins, diverticulitis, hiatial hernia and gastroesophageal reflux.