Paleo, Carbohydrates, and Brain Evolution: the Controversy that doesn’t Exist
Scientists from several European countries in Europe and Australia recently published their hypothesis The Importance of Dietary Carbohydrate in Human Evolution in The Quarterly Review of Biology. Their interesting work tracks through the history of humans to piece together their proposal regarding the role of dietary carbohydrates in the development of the human brain. The article is free to the public here. This article holds importance to all those following a paleo, primal, or ancestral diet with recommendations often based on evolutionary science, with brain development remaining a large component of our dietary history.
In their thought-provoking paper, they propose that:
“plant foods containing high quantities of starch were essential for the evolution of the human phenotype during the Pleistocene.”
The Pleistocene is about 2.5 million to 12,000 years ago, thus around the time where most followers of the paleo diet feel as though the optimal diet was ingrained within us.
Dr. Karen Hardy, a research professor at the Universitat Autònoma de Barcelona, was the lead author of the study. Her research interests include the study of the pre-agrarian diet and the use of plants during this period. She also is attempting to fill the gaps in records for evidence of plant consumption via her research – this is extremely difficult due lack of preservation of plant matter. This most recent work seems to follow along closely with her studies, as she is trying to piece together the role that plants have played in the ancient diet and paleo environment (as taken from her research profile).
So before we go any further let us clarify: this article is a review of several studies as support for a hypothesis led by a researcher whose entire research revolves around providing evidence that plants held a significant place in our evolution. In the words of Jerry Seinfeld, “Not that there’s anything wrong with that,” but something to keep in mind while reading the paper. The unfortunate truth is that most (or all) research eventually turns into attempts to confirm one’s opinion. Sometimes it is more important to know where that initial opinion came from, but I digress.
However, many in the media are presenting this as though it is some form of new substantial evidence or the result of findings from a dig site. This is a review article in support of a hypothesis, so don’t let them trick you.
The Brain Evolution Hypothesis
Simply put, their hypothesis is that starch consumption played a relevant or even large role in the development and enlargement of the brain during human evolution. Their support for this hypothesis comes from three main areas:
1. Salivary amylase genes to help digest starches
2. The development of fire and cooking techniques to aid in starch digestion
3. The protection of tubers from the elements as they remain within the ground
Numbers 1 and 2 above remain unsolved as different data has dated the start of fire at varying times and the relevance of the amylase gene and its emergence does not clearly indicate that the brain required large amounts of carbohydrates for development. That being said, the emergence of a product in our oral cavity capable of digesting a certain food is interesting, especially for those of us who feel that our bodies have molded to the optimal diet over our time on this planet.
Number three above was touched upon the least, which is unfortunate as I find this the most interesting. We were clearly opportunists when it came to food, and as I will discuss below, this may hold more support of their hypothesis than amylase and fire. I have heard Paul Jaminet speak about this dozens of times and always found it interesting. Perhaps from an archeological point of view, it is of less interest or there is less information to go on.
A superficial discussion of these three topics would have been harmless enough while holding significant interest. However with this study, the devil is in the details.
This study discussed the viewpoint that brain development was reliant on carbohydrates. As fat clearly led to the majority of key changes as we morphed to H. erectus with our larger brains and smaller guts, it would be better said that brain development relied on fat, but carbohydrates pitched in. The authors do agree that this shift occurred during the consumption of a high-volume, low-energy diet to a high-energy, low-volume diet, quoting the work of Leslie Aiello. What they do not tell the reader is that Aiello’s work concluded that “the incorporation of increasingly greater amounts of animal products into the diet was essential in the evolution of the human brain.”1 Again, this reference is hardly supportive of their overarching hypothesis, and yet with support from the media, they imply carbohydrates were the driver.
As macronutrient content is nearly impossible to determine, the reader has to question the semantics involved with their view of carbohydrates. Was it a little? A lot? Did the whole diet rely on carbohydrates? This data is obviously difficult to come by, as plant sources of food do not stick around for thousands of years. But, as you will read below, they seemed to turn to recent dietary advice to support such claims. In this regard, the title seems misleading, though I am sure this was to put the crosshairs on the more established theory that fat led us out of apedom.
Now I am not a paleontologist, anthropologist, and archeologist, so these aspects of this work and similar studies always requires a decent amount of effort on my part. That being said, I was gifted a Brontosaurus vertebral body that now has my name on it at the Carnegie Science Museum in Pittsburgh, so I at least have some credibility.
Regardless, I do not have to delve that deep, as Peter from Hyperlipid has already done an excellent job. As the authors set up their support of the “we ate more starches than we think” hypothesis, they discuss our ancestors that apparently, well, ate more starches than we think. Yet, while setting up the reader to believe that variation existed in our distant ancestral diet, the authors imply that contemporary Middle Pleistocene Homo sapiens ate more carbohydrates than Neanderthals. However, the source that they site actually stresses that it is impossible to tell if they ate any carbohydrates due to measuring methods. What they do state is that there is isotopic evidence to suggest that Neanderthals and early modern humans obtained most of their dietary protein from both land and sea animals.2 Sea animals seemed to have come along as part of the diet slightly later, but the work clearly provides little implication of a higher carbohydrate diet.
Peter appropriately concludes that while there is no evidence to say whether the brain needed starch or not during its evolution, and citing a paper that never even comments on this as support is less than stellar.
Other issues with the article follow, and on page 255, they delve into the modern diet and its composition of 40-75% carbohydrates, of which the vast majority is starch. I am assuming this was just a descriptor, but as I read it I almost felt as they were describing this as support for their hypothesis. This obviously threw me for a loop as the weight of our nation has grown almost exponentially since these dietary recommendations were established, while our health has plummeted. Clearly, as the readers of my articles generally agree, the modern diet and its macronutrient composition are anything but healthy.
This is followed by a discussion of the human requirement of carbohydrates, which they state is approximately 170 grams per day. I am not totally sure where this number came from and perhaps it is in reference to an earlier source, as the citation following it is an article regarding fermentation and colon health.3
They later cite the Institute of Medicine and describe 150 g/day of carbohydrates as the practical minimal requirement of daily intake past the age of 4 years. This number strikes a chord with me, as this is generally my absolute upper limit of carbohydrates per day, and would normally be consumed if I am carb loading due to heavy workouts or if the wheels came off during an epic cheat day. While everyone’s upper limit is likely different, stating that this number as the absolute minimal requirement more so signals to me a potential unfamiliarity by the authors with low carbohydrate diets in practice. The constant references to the Institute of Medicine further suggests this as the IOM recommends a diet of up to 65% carbohydrates, which would leave the strongest of willed overweight, hungry, and resentful and I would never follow this recommendation personally or in practice.
Following this discussion, the article ventures into typical The Waterboy territory, where much like foosball, ketones “are the devil.” Similar to above, those of us with professional and personal experience in the low-carb world have heard these false acquisitions a thousand times and there is no good data to support them. Periodic ketosis was and is a normal part of our history through feast and famine.
In the closing part of this section, the authors discuss the potential of animal foods as necessary for long-chain omega-3 fatty acids, such as DHA, which are essential for our brains and neural tissues. However, they then follow that these omega-3 fatty acids can be acquired through plants from the conversion of alpha linoleic acid (ALA). Not only does this contradict their previously mentioned high-energy, low-volume diet required for our brain developments, but it is well-known that the conversion of plant sources to DHA and EPA is anything but efficient or effective. This has been summed up quite nicely by Chris Kresser.
By the end of this section, I realized they were really scratching for support of their hypothesis and it just was not happening. In fact, that lack of support of both their comments on those devilish ketones and the conversion of short-chain omega-3 fatty acids to DHA has already been discussed thoroughly (thanks Rainer Klement for the article).4
But then the media got ahold of it…
It their typical fashion, the media boldly exclaimed that “Paleo is wrong” and “High-carbohydrate diets were what our ancestors ate.” I originally was going to post some of these articles, but this seems to only fuel the misinformation. You can simply do a Google search if interested. Several commented that paleo should be more than a high-protein diet.
While a high protein paleo diet was originally discussed by Cordain,5 few would consider the present definition of paleo as high protein, but rather high fat. Yet, nutritionists and medical professionals alike continue to criticize paleo for being high fat, high protein, and now no-carbohydrate. Straw-man arguments emerge left and right.
The media response to this study criticizes the modern view of paleo, yet is basically confirming what we in the paleo world have been supporting for quite some time. An optimal paleo diet is likely high in fat, low in protein, and low in carbohydrates. This study hypothesized that starches may have made up some of our original diet, without any quantifiable amount given as this is likely impossible to ascertain.
Paul Jaminet discussed this in his masterpiece Perfect Health Diet years ago. John Durant made similar claims about starches in The Paleo Manifesto, which is my favorite book of the year and a must read for anyone interested in their health.
This article further supports these views, so I am not really sure why the media jumped on the carbohydrate part, except of course to sell some sort of controversy (fyi: there is none). Starches and white rice, unlike grains, are more “safe” when it comes to the potential inflammatory components of grains, including elevated amounts of phytic acid, gluten, and lectins. In the grand scheme of things, it is not so black and white and they are not entirely free of toxins like oxalate and a few others. This has been hotly debated online and at the Ancestral Health Symposium back in 2012.
While I find the article extremely interesting and am thankful to the authors for adding to the bulk of the literature assessing ancestral diets, their conclusions left me a little dumbfounded. Before long, I felt like I was reverting back to the food pyramid and the plethora of dietary mistakes over the past 30 years.
The first time I read this article I liked it. I think starches are fine in reasonable amounts for those who tolerate them (especially after a workout) and this article did not change much in that regard. I also knew it would question some of my dietary views and narrative, and I always aim to read articles that force me to critically analyze my views. In fact, I tried to be so non judgmental with this article, that I missed some elements that really irked me the second time I read it.
I thought the article made some good points. Starches like sweet potatoes and white rice have been a steady part of my diet, especially after workouts, and I look forward to continually eating them in small amounts. This article, while interesting, clearly provides no change in my diet or those who consume a Paleo diet with “safe” starches.
However, the importance of carbohydrates in brain development was clearly embellished in this article and digging deeper provides many holes in the hypothesis. While still an interesting read, any usage of this article as an attempt to push a low-fat diet or even significantly increasing carbohydrate consumption above a reasonable level is clearly misguided.
1. Aiello, L. C. & Wheeler, P. The Expensive-Tissue Hypothesis: The Brain and the Digestive System in Human and Primate Evolution. Curr. Anthropol. 36, 199–221 CR – Copyright © 1995 The University (1995).
2. Richards, M. P. & Trinkaus, E. Out of Africa: modern human origins special feature: isotopic evidence for the diets of European Neanderthals and early modern humans. Proc. Natl. Acad. Sci. U. S. A. 106, 16034–9 (2009).
3. Wong, J. M. W., de Souza, R., Kendall, C. W. C., Emam, A. & Jenkins, D. J. A. Colonic health: fermentation and short chain fatty acids. J. Clin. Gastroenterol. 40, 235–43 (2006).
4. Cunnane, S. C. & Crawford, M. A. Energetic and nutritional constraints on infant brain development: implications for brain expansion during human evolution. J. Hum. Evol. 77, 88–98 (2014).
5. Cordain, L. et al. Origins and evolution of the Western diet: health implications for the 21st century. Am. J. Clin. Nutr. 81, 341–354 (2005).
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