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Big Brains Do Not Need Carbs

August 20, 2015
Big Brains Do Not Need Carbs image

Evolution. It is a complex and interesting process.1,2,3,4,5,6,7,8,9,10 Whether you agree with Jerry Coyne or not, there is much fascination with what exactly has led us to the current bodies and brains which we inhabit.11,12,13,14,15,16,17,18,19,20 Two weeks ago The Quarterly Review of Biology published a controversial paper entitled “The Importance of Dietary Carbohydrate in Human Evolution.”21 Its preceding press release22 added “Big Brains Needed Carbs,” ensuring the controversy-eager media would jump all over the publication, including the University of Sydney, home of the GI Foundation. Of course this media frenzy23,24,25 is without critical analysis, and is simply a regurgitation of the same story. So the researchers behind this paper argued that as humans evolved from our Paleolithic ancestry, we needed carbohydrates (particularly starch) in order to develop larger brains.

While certainly generating a large amount of buzz and receiving tremendous media attention, this scientific paper is severely flawed. Quite frankly, it is fairly baffling that it was able to survive the peer review process at all. There are a number of points that are incorrect, so without further ado, let’s delve into the details of exactly why we did not need starch, in order to help develop our current brains.

To start, researchers for the paper cite the use of fire as a key point in their argument. However, they incorrectly lead the reader into believing that the timeframe for humans using controlled fire was about 300,000-400,000 years ago, when they themselves contradict this with the statement that “the timing of widespread cooking is not known.” This is likely one misfire that should have been caught in the peer review process. In reality, our ancestors could only make fire in a controlled fashion, starting about 75,000 to 125,000 years ago.26,27,28,29,30,31,32,33,34 Hominid encephalization (enlargement of the brain), by contrast, began about 2 million years ago. 35,36,37

This is in addition to the researchers’ lack of scientific support for starch consumption compared with non-starchy vegetables, and the necessity of these foods in the human evolutionary process. And, if one were to veer to modern research, they would plainly see studies have proven a Paleo diet does not need to be high in starches or carbohydrates to vastly improve health.38,39 Further, it is widely accepted that hepatic de novo gluconeogenesis (a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates) can provide brain and placental tissue with all the glucose required even on a carbohydrate free diet. The fact that previously published research by the paper’s author supports this,40 is a glaring inconsistency that is hard to reconcile.

Big Brains Do Not Need Carbs image

Figure 1: The Carnivore Connection hypothesis 1 and association with recent increased prevalence of insulin resistance (IR) and type 2 diabetes in susceptible (e.g., Pima Indian) and nonsusceptible (e.g., European) populations.

Suggesting early Homo acquired the capacity for endurance running as essential to exhaust prey is a weak assumption. This reference to persistence hunting, a method of hunting that utilizes the better thermoregulation of humans as compared to their prey, is only successful in a few select climates where thermoregulation is an issue. More importantly, the authors are clearly unaware of the research that measured the energetic cost of human running at different speeds.41 Researchers found, contrary to previous beliefs, individual humans do have optimal running speeds with respect to energetic cost, but it was also demonstrated “that the use of persistence hunting methods to gain access to prey at any running speed, even the optimum, would be extremely costly energetically, more so than a persistence hunt at optimal walking speed.” No starch is necessary for that. Even if the analysis on running efficiency were incorrect, and researchers proved persistence hunters did run at high intensities, the authors would need to explain the disconnect with their hypothesis with the fact that many present-day elite endurance athletes are succeeding on a low carbohydrate diet.

The fact is, our ancestors likely ate whatever they could – a fact, which is noted by modern Paleo diet researchers.42,43 Current science supports the notion that dense acellular carbohydrates in the diet promote an inflammatory microbiota, and may be the primary dietary cause of leptin resistance and obesity.44 This is why modern Paleo diet research is conducted with the design of eliminating foods not available during the pre-agricultural period – rather than focusing on specific amounts and quantities of foods.

Big Brains Do Not Need Carbs image

These researchers also fail to cite a very recent paper, which examined nuclear genome sequence data from Neandertals, Denisovans, and archaic anatomically modern humans.45 It was concluded "salivary amylase gene (AMY1) duplications were not observed in the Neandertal and Denisovan genomes, suggesting a relatively recent origin for the AMY1 copy number gains that are observed in modern humans. Thus, if earlier hominins were consuming large quantities of starch-rich underground storage organs, as previously hypothesized, then they were likely doing so without the digestive benefits of increased salivary amylase production."

As you can see, there are a myriad of flaws in this paper. The conclusions reached by the authors contradict everything we know about uncooked starch metabolism in our gastrointestinal tract, the archaeological evidence for fire production, and the brain’s requirement for docosahexaenoic acid (DHA).46,47 DHA was obtained by our ancestors, from animal foods – not starch - in order to synthesize nervous tissue.48,49

Lastly, perhaps one of the most interesting flaws in this paper is that many scientific studies concluded chronically elevated blood sugar (which is directly influenced by carbohydrate consumption) is correlated with dementia.50 Certainly this is the exact opposite conclusion than the one reached by the paper’s authors, who would have you believe that we needed carbohydrates in order for our brains to thrive and develop.

Hopefully, it is clear we certainly did not need starch to develop our current brains, and in fact, too many carbohydrates (including starches) impair brain processes.51,52,53 The problem with this conclusion is not scientific – it is economic. For you see, it is quite easy to continually churn out starch-heavy foods and make a profit – as these foods are very cheap to produce. And, without an endorsement of carbohydrates, how could a company justify selling sugar water to us, en masse?54 Thanks to a diet rich in animal products and fat, you have a big enough brain to recognize the real scientific evidence and that unethical influences are at play here. Definitely some real food for thought.


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