Timeline of the changes in lifestyle and its effects on the human genome.
Several anthropological analyses have looked at the importance of diet during human evolution, and it is believed that dietary habits have lasting effects on us through our genetic profiles. Scientists also believe that dietary differences contribute to the dramatic morphological changes seen in modern humans as compared with non-human primates and that they can change the gene expression and their functions.
In other words, what our ancestors ate has largely shaped our food preferences; We truly are what we eat.
A new study looked at hundreds of human genomes highlights that populations in different regions of the world have evolved for dietary habits with different proportions of meat and vegetables .
For instance, Europeans from the southern regions are better equipped for high-plant diets, while people from other regions (Inuit of Greenland), are more optimized to process lots of meat and fat.
It is suggested that these genetic changes might have been a driving force for human evolution. A different study also explains that the biggest divergence between the human and chimpanzee genomes is found among genes that control metabolism and are closely associated with diet .
Dietary and Environmental ChangesTransition from Hunter-Gatherers to Farmers – Changes in Genes?
The concept of food is essentially a choice between two things, what is available to eat as well as what a species has evolved to eat.
Our ancestors were exposed to different kinds of food availabilities, depending on the climate changes around them. It is these very changes that drove evolution. Dietary choices, in turn, have affected the genetic blueprint of our ancestors and thus ours to a certain extent.
Meat has long been the protagonist in the evolution of the human diet. Some scientists believe that the evolution of the larger brain of our ancestor, Homo erectus, about two million years ago is largely due to the consumption of meat that yielded a calorie-dense diet. This is opposite to the low-calorie plant diet of apes. And it is also why H. erectus had a smaller gut, which freed up a lot of energy that could be consumed by the larger brain. Overall, it is safe to say that since the time of our ancestors, the human body has depended on an energy-dense food diet, of which the starring role has been meat.
The Neolithic revolution began 10,000 years ago. Before that, during the Paleolithic age, European populations were hunter-gatherers and their diet was animal-based. However, the arrival of farming 8,000 years ago shifted the eating habits of Europeans to more plant-based diets.
Given these historic changes in living trends and the subsequent effects that manifested in the human diet, anthropologists have had a difficult time analyzing this transition, especially around whether farming was an advancement to human health or not. In particular, by giving up our hunter-gatherer lifestyles for food security such as growing crops and raising livestock, did humans let go of a healthier diet and more fit bodies?
The arrival of farming did not just have lifestyle changes. We now know that any change in dietary habits is evident in the genes of Europeans, and those adaptations followed the dietary trends of the time (Figure 1) . What is more is that this has implications for the fields of nutrigenomics as well as nutrigenetics that investigate how diets have evolutionarily manifested themselves on the human genetic blueprint. A number of studies have successfully identified specific signatures of the modern human genome’s adaptation to dietary changes [e.g. 4, 5, 6, 7]. These studies have shown that it is possible to find specific markers in human genes related to dietary changes. These markers come in the form of changes in coding regions, regulatory regions and gene copy number, and they can cause changes in the human genome.
FADS – the Genes Responsible for Processing of Meat and/or Plants -and What We Know About Them Today
Strictly technically speaking, what are the genetic variations that are the result of dietary changes?
Genetic variations across the human genome in the form of single nucleotide polymorphisms (SNPs), copy number variants, insertions and deletions are responsible for the modifications of an individual’s response to diet. And while genetic polymorphisms might or might not have an effect on the structure or function of the products of genes, they are still responsible for the genetic differences among humans. Based on the dietary habits of our ancestors, we have been ‘pre-programmed’ to prefer certain foods over others. This is because their diets have shaped their genetic blueprint which they have passed on to us.
The human genome contains DNA regions that contain two genes that are called “fatty acid desaturase 1 and 2,” or simply FADS1 and FADS2. These two genes are in control of how the body converts short-chain poly-unsaturated fatty acids (PUFAs) to long-chain PUFAs which promotes the health of many tissues, such as the muscles and the brain.
FADS Genes in European Populations
The evolutionary changes that the FADS of Europeans have undergone can be traced back to the Bronze Age. The FADS genes have mutated to make more long-chain PUFAs, which means that diets have been higher in vegetables and grains which produce short-chain PUFAs. Meat, on the other hand, produces long-chain PUFAs. An example of this evolutionary manifestation are the FADS genes of Intuit groups. The Intuits’ diet is high in animal fats from ocean mammals since their FADs genes are programmed to produce fewer long-chain PUFAs.
Classification of European cultures in 3500 BCE based on hunting and farming lifestyles as well as the distribution of the farming-adaptive genetic markers.
On the other hand, it is believed that the FADS variants of European populations are a consequence of agricultural lifestyles that resulted in diets that are predominant in wheat and vegetables. With the practice of farming, Europeans and Middle Eastern populations were taking in more short-chain PUFAs. This resulted in the survival of the fittest:those who could convert short-chain PUFAs to long-chain PUFAs passed on their genes to the next generations (See Figure above).
A recent study that was conducted at Cornell University  demonstrates that vegetarian diets of European farmers resulted in an increase in a gene variation, or allele, that signals cells to create enzymes that helped farming individuals metabolize plants .
Ancient DNA analysis showed that the animal-based diets of European hunter-gatherers favored another version of the same gene, namely one which limits the activity of FADS1 enzymes and is thus more suited for individuals with meat and seafood-based diets . This was prior to the arrival of humans’ farming. As such, analyses demonstrate that this allele frequency or prevalence decreased among Europeans that practiced plant-based diets. This was until the Neolithic revolution, after which the frequency rose significantly. At the other end of the spectrum, frequency of the opposite version of the same gene increased until the arrival of farming, decreasing sharply after that.
Lastly, in addition to diet-specific gene frequency changes, location specific changes have been observed as well, whereby a frequency gradient of these alleles was noted from north to south since the Neolithic era. Farmers’ diets were mostly plant-based in the south, whereas the northern diets were more marked by dairy as well as seafood .
Nutrigenetics and You: The Future of Personalized Diets – Paleo? Eat Like Your Ancestors?
Overall, there is no such thing as one ideal human diet and there is no doubt that dietary habits affect genetic expression. Even though the field is relatively new, it is gaining traction. The realms of nutrigenetics and nutrigenomics have a vast potential to enable nutritionists and physicians to personalize health and diet recommendations. As a result, preventive medicine, diagnostics and therapeutics could be individualized or optimized so that each patient has a unique set of dietary or nutritional recommendations based on their genetic profile. Health counseling based on the outcomes of a nutrigenetic analysis have been shown to be more successful than conventional diet counseling .
Still, regardless of the definitions and explanations behind dietary effects on genes and vice versa, it is evident that the human genome has responded to human diets for thousands of years.
As such, we are not meant or equipped to consume the same food items that our ancestors had in 50,000 years ago as hunter-gatherers. We are more likely to have the ability to process nutrients that our ancestors ate only a few thousand years ago. Rest assured that even the food that our great-grandparents consumed is already affecting the FADS inherited by our children.
So what does all of this information mean for you, today?
Knowing that there are specific genetic markers within the FADS genes, individuals who are interested in finding out which type of diet suits them best based on their genetic profile would be able to obtain that information based on the screening of their FADS genes and the information they contain.
Several SNPs have already been looked at in association with dietary habits, and there are most likely going to be more. This would eventually lead to more optimized genetic screening as well as more personalized nutritional profiles and dietary suggestions.
Keep in Touch to Stay Informed
If you have already conducted genetic testing or you are interested in finding out more about nutrigenetics and nutrigenomics and how they apply to you, if you find this field interesting and/or if you simply would like to remain informed, please get your invitation at www.ginihealth.com and subscribe to the blog for regular updates.
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