Western Diet and the Human Genome: Part 3 - by Pedro Bastos
Editor's note: Pedro Bastos has authored a paper discussing the human genome, Western diet, and chronic, degenerative diseases that are prevalent in Western countries but which are largely absent in hunter-gatherer societies. This is the third and final installment of this paper.
Absence of Cardiometabolic Risk Factors in Primitive non-Westernized Populations
The Neolithic and Industrial Revolution and Its Consequences
About 11 thousand years ago, the Agricultural Revolution that took place in the Middle East forever changed the diet and lifestyle that had shaped the human genome for more than 2 million years. Some of the more significant changes were the use of cereal grains as staple foods, the introduction of legumes and other plant foods, non-human milk in the human diet brought about by the domestication of animals, and later on sucrose and distilled alcoholic beverages19, 76.
Table 6. Foods introduced by the Industrial Revolution.* Chronology Food
1800 D.C. Universal availability of Refined Sugar
1860 D.C. Meat from Obese grain fed animals
1880 D.C. Universal availability of Refined Cereal Grains
1897 D.C. Hydrogenated vegetable Oils
1910 D.C. Universal availability of Omega 6 rich Vegetable Oils
1970 D.C. (USA) High Fructose Corn Syrup
*Adapted from Cordain et al.19, 76
Nevertheless it was the Industrial Revolution (Table 6) and the 20th Century (with the advent of the junk food industry, generalized physical inactivity, introduction of various pollutants and avoidance of sun exposure) that caused the biggest changes in terms of diet, which were:
1. Macronutrient Distribution
The percentage of total food energy derived from macronutrients in Pleistocene diets would most certainly be different than current official dietary guidelines (Protein – 15%; Carbohydrates - 55-60% and Dietary Fat ? 30%)166. Cordain estimated76 the following distribution for Pleistocene diets, as a percentage of total daily caloric intake: Protein (19-35%), Dietary Fat (28-58%) and Carbohydrates (22-40%).
Even though the Daily Protein RDA is 0.8 g/kg of body weight167, there is evidence that athletes need higher amounts (which is why 1.2-2 g/kg/day is being increasingly recommended168-170) The elderly also need a higher intake to prevent or attenuate Sarcopenia171, 172 and Osteopenia173, 174, especially in the context of a high fruit and vegetable diet (a net base yielding diet)175.
Moreover, High Protein Diets (> 20% of caloric intake176) have been shown to improve Dyslipidemia177-187 and insulin sensitivity93, 178, 181, and are potentially effective strategies in obesity188-190, and Metabolic Syndrome associated Hypertension191-194. Furthermore, they may decrease the risk of stroke195, Hyperhomocysteinemia196 and Ischemic Heart Disease197, without adversely affecting kidney function in individuals without pre-existing kidney disease198-202. Nevertheless, there is an hepatic urea synthesis limit (2.6 - 3.6 g/kg/day)160, 203 that shouldn’t be crossed.
There are concerns that a pre-Agricultural Revolution-type diet may have consisted of a high intake of fat, with a corresponding increase in Cardiovascular Disease (CVD) risk. In that regard, it should be mentioned that the absolute amount of dietary fat is less important than the type of fat31, 123, 204, 205. Moreover, the majority of fats ingested by HG were monounsaturated, which have a beneficial effect in the lipoprotein profile123. Finally, the consumption of industrial trans fatty acids was virtually nonexistent 76, 123.
2. Fibre and The Glycemic Load
During the Pleistocene, most carbohydrates came from the consumption of wild fruits, berries, vegetables, and sometimes tubers, with cereal and honey intake being very scarce32, 19, 76. Therefore, the Glycemic Load (GL) was significantly lower than the GL of Western diets76, since even whole grains possess a higher GL than most fruit and vegetables206.
Furthermore, on average Pleistocene diets had more fibre76 than the typical Western diet, because most of the fibre today is derived from cereal grains, whereas until the Neolithic it came from fruits and vegetables. On a calorie per calorie basis, fruits and vegetables have, respectively, two and eight times more fibre than whole grains76.
Another food group that was not part of the Pleistocene diet, but is considered a staple today is dairy76. This is highly relevant since milk, yoghurt and some lactose containing cheeses – despite having a low GL – elicit a very high insulin response207-211.
The increase in GL and insulinotropic potential of the diet, coupled with a decrease in dietary fibre and an increase in fructose intake76, may be one of the causes of the high incidence and prevalence of Epithelial Cell Cancers, Obesity, Hypertension, Metabolic Syndrome, Gout, Coronary Heart Disease (CHD), Acne, Myopia and various gastrointestinal problems76, 99, 134 in industrialized countries.
3. Omega 6/Omega 3 ratio
Long Chain Polyunsaturated Fatty Acids of the omega-3 and omega-6 family were part of the hominin diet for millennia. Also, for most of human existence (e.g. the Palaeolithic era), the omega-6 / omega-3 ratio in the human diet has been estimated to be76 between 1:1 and 3:1 – similar to the ratio found in the traditional diet of Greece until 1960, which parallels a low incidence and prevalence of CHD in that country205. In contrast, the ratio in United Kingdom, Northern Europe and the USA is above76, 212 10/1, and is rising to 50/1 in certain urban areas of India213. This elevation of the omega-6 / omega-3 ratio may increase the risk of CHD212, 213, cancer214, psychiatric disorders215 and Osteoporosis216 among other diseases.
4. Micronutrient Density
Calorie per calorie, fish, shellfish, meat, vegetables and fruit present a higher micronutrient density76 than cereal grains (especially the refined version), milk (with the exception of calcium), sugar and refined oils. Therefore, current food choices – together with soil depletion, modern food transport, stocking and culinary methods are the main reasons why a significant percentage of the developed world’s population doesn’t reach the RDA for various vitamins and minerals76, 217-225. This is another factor explaining the high prevalence of chronic diseases in industrialized countries 76, 226.
Conclusion
In conclusion, the adoption of a diet and lifestyle very different from the one that shaped the human genome for more than 2 million years is a likely explanation of why chronic degenerative diseases are epidemic in Western countries. On the contrary, regular physical exercise156-158, sun exposure according to latitude and skin colour (in order to maintain plasma 25OHD3 above 40 ng/ml227), adequate sleep6, 228-230, and the adoption of a diet similar to the one followed by Pleistocene HG (fish, shellfish, eggs from free range chickens, muscle and organ meat from free range grass fed animals, fruits, vegetables, roots, tubers, nuts and seeds) may lead to optimal health.
References are listed on Cordain's official site given their extreme length.
