Western Diet and the Human Genome: Part 2 - 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 paper will be published in The Paleo Diet Update in three parts, of which this is the second.
Absence of Cardiometabolic Risk Factors in Primitive non-Westernized Populations
Counter-Arguments
It could be argued that these more primitive populations are genetically protected against the chronic degenerative diseases that we see in industrialized countries. Nevertheless, when these individuals adopt a more Western lifestyle, their risk for chronic degenerative diseases is similar to – or even greater than – Western populations41, 77, 90-92, 123, 124, 137-154. This susceptibility is reversed in some cases when they return to their original, primitive lifestyle93, 155.
This demonstrates that the superior health markers, body composition and physical fitness of HG and other populations minimally affected by modern habits aren’t due to genetics, but to the environment. It also demonstrates that there aren’t genetic adaptations that fully protect the HG populations that adopted modern diet and lifestyles from chronic degenerative diseases115 – so-called Western diseases32, 76.
In reality, two apparently different individuals, when exposed to the same modern environment (Western diet, physical inactivity, inadequate sleep, insufficient or excessive sun exposure, use of recreational drugs, smoking, pollution, etc.) will always express a suboptimal phenotype, which could be considered pathological, depending on genotype76, 156-158.
Therefore, it can be argued that modern Homo Sapiens are still adapted to a pre-agriculture diet and lifestyle.
Using this notion as a template, together with epidemiological evidence, animal and in-vitro studies, as well as human intervention trials, it is possible to establish dietary and exercise guidelines that are in synch with modern human physiology.
Another typical counter-argument is the short average life-expectancy of HG populations, which is not a valid argument since this marker is highly influenced by childhood mortality. Today, the frequency of childhood mortality is much lower not because of a healthier lifestyle, but thanks to better sanitation, vaccination, quarantine policies and medical care73. Moreover, an estimated 20% of the HG population reaches age 60 or beyond without the signs and symptoms of chronic degenerative diseases that afflict the majority of the elderly in industrialized countries73. Furthermore, in these countries, the incidence of some of these diseases (such as Obesity and Type II Diabetes) is now increasing in younger age groups32, 76, 77.
Finally, the fossil record suggests that when HG populations made the transition to an agricultural pattern of subsistence, their health status and lifespan decreased32, 124, 159.
The Ancient Environment
What was the environment that had the most influence in shaping the human genome?
With the help of anatomical, biomechanical, and isotopic analyses of various hominin skeletons, the archaeological and geological evaluation of their habitats, and ethnographic studies of various HG societies (whose diet and lifestyle resembled the Palaeolithic diet and lifestyle), various researchers6, 71, 75, 76, 123, 160-165 have concluded that despite the existence of different diets and lifestyles that varied due to differences in geography, ecological niche, season and glaciations, they all had the following characteristics:
1. Regular sun exposure165.
2. Sleep patterns in synch with the daily variation in light exposure6.
3. Regular physical activity, since it is necessary to obtain food, build shelter and for safety158, 162, 163.
4. Common food sources (see Table 5), including:
Table 5. Foods consumed during the Pleistocene.* Foods available Foods not available
Insects, fish, shellfish, wild terrestrial animal and bird muscle tissue, fat and organs Dairy (except for human milk until 2-4 years old)
Plants Cereal grains (with the exception of occasional intake in the upper Palaeolithic)
Roots Legumes
Tubers Isolated sugar
Berries and wild fruit Isolated oils
Nuts Alcohol
Seeds Refined salt (even sea salt would only be available for shore based populations who may have deep their food in sea water)
Honey (occasional intake)
*Adapted from Cordain et al.19,76
Be sure to read next week's newsletter for part 3 of this informative paper.
References:
Due to the large number of references for this article (230), the list of references has been published as a PDF which you may download from our web site.
Part 1 of Pedro's paper, published in last week's newsletter, prompted the following reader response:
Greetings Dr. Cordain and Pedro:
Your "Western Diet and human genome" article, part one, is very interesting.
I have a question about it, and not having seen parts 2 and 3, perhaps the question will be addressed then. My question is about metabolic individuality.
Is that a factor of epigenetic changes which have not influenced the arrangements of the A<G<T<C nucleotides, but the outer shield encoding of the genome?
Have these changes occurred over millinea, or as food choices changed (vegetarians to meat based in the, say, Eskimos), based on the environment our ancestors found themselves in as they searched for new horizons due to population pressures, changed the actual DNA, so that their metabolisms actually changed to maintain decent / optimum health for a new environment?
Thank you for your input.
Pieter Dahler, DDS. MD.
Dear Dr. Dahler,
Thank you for your comments and support, and for your excellent questions.
I believe both mechanisms operate to "produce" what Roger Williams described as "biochemical individuality".
Nevertheless, two apparently different individuals, when exposed to the same modern environment (western diet, physical inactivity, inadequate sleep, insufficient or excessive sun exposure, use of recreational drugs, smoking, pollution, etc.) will always express a suboptimal phenotype, which could be considered pathological, depending on genotype. For a population in general, it seems to make sense to establish general guidelines about sleep, sun exposure, diet, exercise and other lifestyle habits.
Nevertheless, single nucleotide polymorphisms (SNPs), which only comprise 0.1% of the human genome, are responsible for all the morphological, physiological, biochemical and molecular differences between two individuals. This means that there are individual differences in the way a human being digests, absorbs, transports, metabolizes, uses and stores nutrients. Indeed some of these individual differences arose after Homo Sapiens left the African continent due to various environmental pressures, but many were already present before Homo Sapiens left Africa.
Then there are, as you said, the epigenetic markers. These are heavily influenced by maternal nutrition, which was presumably worse after the Agricultural Revolution, giving rise to suboptimal phenotypes, and influencing individual dietary needs.
In conclusion, an ideal diet for a general population may not be totally applicable for specific individuals.
I hope this helps.
Best regards,
Pedro
