The negative impact of the “Western” diet (high fat, high-sugar, high-salt, and overly processed) on health has lead some to suggest that what is required is a return to our traditional diets from the paleo times – 2.6 million to 12,000 years ago (1); pre-agricultural.
Is this correct? Does science support the popular health claims of a Paleo Diet pattern? The million dollar evolutionary question is: How are humans genetically designed to eat for optimal health?
The idea that our current diet is mismatched to our evolutionary history is not new and was initially proposed in 1985 by Eaton and Konner (1). They suggested that a “Paleolithic diet” – a diet that tries to mimic the ancestral diet and includes high protein, less total fat, increased essential fatty acids, lower sodium and higher fibre – is healthiest (1). Proponents suggest that most of our “modern” human traits evolved during the Paleolithic period and that our environment and culture has changed more rapidly than our genetics, creating a mismatch. As a result, we are experiencing “diseases of civilization” (2).
A recent article from Nutrition Reviews (3) identifies three concerns and weaknesses with the Paleo diet theory.
1. The “paleo” diet was likely not universal.
The basic premise of the “paleo” diet is that there actually was a uniform paleo diet. What this would mean is that every human living during the paleolithic time – a very long time – ate the same diet and had access to the same types of foods. Given the current cultural and environmental influences on diet this is unlikely! We know that geography, food availability, seasonality and climate all affect our ability to obtain food (4).
You can rest assured that your typical paleo human was not going to the grocery store to buy the same foods as their paleo cousins living thousands of kilometres away and millions of years apart! Two questions immediately come to mind:
- If the paleo diet is optimal for health, exactly *which* paleo diet is it?
- Is it really possible to mimic the paleo diet with our current food sources?.
In all truthfulness, it is probably the flexibility and plurality of the human diet that has contributed to the success of our species. With this in mind, the way forward is not to further restrict intakes but to broaden our range of foods (3).
Indeed, this may become more important as our population continues to grow and our traditional food resources and practices become more stressed. Even if the “paleo” diet was found to be optimal for health, it is unlikely that it is sustainable and the select foods sufficiently available to support our population (5).
2. Ongoing genetic variation.
The paleo diet theory ignores the small evolutionary changes – yes, there have been some – of the more recent past or assumes that they are not significant enough to outweigh traits evolved during the paleolithic time (3).
There is strong scientific evidence for genetic changes that are linked to changes in our diet and subsistence, which have occurred SINCE the paleolithic times. For example, the paleolithic diet suggests the omission of grains and dairy, as these were not traditionally consumed during paleolithic times. However, DNA evidence shows that some humans have genetic adaptations that allow for lactase persistence (6). Lactase persistence is the ability to continue to produce the enzyme lactase into adulthood and thus breakdown dairy products.
The ability to consume dairy products would have been an evolutionary advantage to pastoralist populations as it would have provided them with an uncontaminated source of fluid as well as protein, calcium and other nutrients. There have also been changes in the number of genes that regulate the production of amylase – an enzyme needed to breakdown starch (7). What this means is that modern humans have adapted to starchy foods as compared to their paleo ancestors.
Evolutionary theory assumes that these adaptations are advantageous or else these individuals would be less likely to survive and the traits would not be based down. Is it unhealthy to consume dairy products if you have evolved to do so?
3. Human dietary behaviours are not determined solely through genetic means.
The majority of scientific research finds that the body actually doesn’t know best. What this means is that the body is not making conscious decisions that drive food choices based on its physiological needs (8).
For example, when you crave that deep-fried, sugar-coated doughnut that is not actually your body telling you that the doughnut has the nutrients you need and is the healthiest choice you can make! It’s the same with the paleo humans – it wasn’t their genetics telling them which foods to eat based on what their bodies needed…
The majority of our dietary behaviours are socially learned and based on the developmental environment. If anything in our genetics is affecting our food choices, it seems to be fetal imprinting. There is more evidence to support that the fetal nutritional environment plays a larger role in body composition and metabolic health than the genetic make-up of an individual’s prehistoric ancestors (3). This isn’t to say that our prehistoric genes don’t have an impact at all; however, they are not the sole determinant of nutritional health.
No Baloney’s advice? We are not in any way suggesting that processed foods are the way forward. Nor, are we suggesting that the current “Western” diet is one that promotes optimal health. Healthy changes to our dietary patterns are definitely needed! However, it is also unlikely that the Paleo diet is the way humans were “meant” to eat and a return to this diet will solve all of our health problems.
The paleo diet, limits human dietary behaviour and omits foods that are healthy and ecologically more stable such as legumes. We really can’t feed the world on grass-fed woolly mammoths!
- Eaton SB and Konner M. Paleolithic nutrition: a consideration of its nature and current implications. N Engl j Med. 1985;312:283-289.
- Knight C. “Most people are simply not designed to eat pasta”: evolutionary explanations for obesity in the low-carbohydrate diet movement. Public Underst Sci. 2011; 20:706-719.
- Turner BL and Thompson AL. Beyond the paleolithic prescription: incorporating diversity and flexibility in the study of human diet evolution. Nutrition Reviews. 2013;71(8):501-510.
- Garn SM et al. What did our ancestors eat? Nut Rev. 1989;57:337-345.
- Frank-White NE et al. The effect of dietary & transportation choices on climate change. Food Nutr Sci. 2011;2:482-485.
- Holden C et al. Phylogenetic analysis of the evolution of lactose digestion in adults. Hum Biol. 1997;69:605-628.
- Perry GH et al. Diet and the evolution of human amylase gene copy number variation. Nat Genet. 2007;39:1256-1260.
- Galef BG J. A contrarian view of the wisdom of the body as it relates to dietary self-selection. Psychol Rev. 1991;98:218-223.