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Did a Low-Starch Diet Help Drive Human Evolution?

By Casey Thaler, B.A., NASM-CPT, FNS
March 7, 2020
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The subject of human evolution is both fascinating and complex. Human beings evolved from fairly primitive creatures to the most advanced species on the planet. How and why did this happen? It’s a question that scientists have pondered for hundreds, if not thousands, of years. In the exploration of this subject, many researchers have focused on the study of the human diet—that is particularly true at The Paleo Diet. Now, many mainstream outlets have started to ask the question: Did humans evolve to eat lower carbohydrate diets, and do those diets provide us with a better chance of survival and health?

When it comes to the science, a specific gene, AMY1, appears to have played an important role in our development and diet over the years. [1] The gene’s function in starch digestion begins in the mouth; [2] your saliva contains an enzyme encoded by AMY1, and it starts breaking down starch when you chew your food. [3] There is genetic variability, with regard to the quantity of copies of this specific gene, in humans. Interestingly, those with more copies break down starch faster. [4]

However, other primates do not possess that same genetic variability. [5] (Any scientist reading this article should be intrigued by that sentence.) That fact suggests the genetic variability seen in humans may have been an adaptation that helped the species rise to the top. In other words, our evolution may have been aided by our consumption of starchy foods. Furthermore, we may have developed more copies of this gene because it provided an evolutionary advantage.

However, there’s a scientifically surprising fact about the gene variation: Those with different levels of the gene all have different microbiomes. [6] Some research has even shown that weight gain is associated with variations in the gene, another scientifically intriguing suggestion. [7]

Other research has shown that people with fewer copies of AMY1 are almost 10 times more likely to gain weight, when compared to those with more copies of the gene. [8] This is a staggering fact, and one that may not only hold the key to understanding our evolution, but also potentially understanding obesity.

Other studies have shown that boys with lower numbers of the AMY1 gene are associated with having a higher body mass index (BMI). [9] In essence, the fewer numbers of the gene you possess, the more likely you are to be overweight. This research suggests that people can react differently to a particular type of food, and even to the same amount of that food. While one person may gain weight, another may not.

Which begs the question: For those people with fewer copies of the AMY1 gene, what foods should they limit to avoid gaining weight? In short, starchy foods. [10] A low-carb diet is a favorable choice.

Evolutionary Advantage?

Did consuming starch provide us with an evolutionary advantage? Not necessarily. Since the Paleolithic era lasted over 2 million years—far longer than the relatively short period of time that we’ve had to adapt to starchier diets (around 10,000 years)—it is much more likely that evolution may have occurred in response to non-starchy foods. [11] However, the question is still up for debate.

What does this mean from a more practical level? What foods are better to consume? Quite simply: tread carefully with the starches, including foods like potatoes, peas, corn, rice, grains, beans, and pasta. If you’re following a Paleo Diet, you are avoiding these foods already. It would be interesting to see if there is a connection between the level of success one sees on a Paleo Diet—which almost completely omits these foods—and the number of AMY1 gene copies a person carries.

What about those people with more copies of the AMY1 gene? They could, hypothetically, consume starchier foods and keep weight low. However, as the science of The Paleo Diet makes clear, these foods do not provide good nutrition and have a vast array of downsides. So, we recommend refraining from them regardless of your genetic makeup.

Is there, then, an evolutionary advantage to having fewer AMY1 genes? The research suggests those with fewer copies of the AMY1 gene can consume a low-starch diet based around our Paleolithic ancestors and see very favorable results. This scientific evidence supports the notion that eating foods low in starch may have actually driven human evolution. If, by extension, consuming a low-starch diet caused problems in any element of the population, then this would not have been an advantageous development. However, that is not the case.

Since starchy foods have very little nutritional content, very few upsides, and are now associated with increased obesity in a large percentage of the population who have fewer copies of the AMY1 gene, the question becomes: Why would humans continue to eat starchy foods? Economics are clearly one factor. Starchy foods are inexpensive. That’s part of why, for the first time in history, those in lower income brackets have higher rates of obesity. Unfortunately, while many people would love to eat healthier, they simply can’t afford to do so.

However, even if your budget is very tight, there are still small changes that can be made which will go a long way towards supporting your health. Reducing starchy foods—regardless of how many AMY1 genes you have—is a good start.

If you enjoyed this article, check out Casey’s new cookbook!

References

  1. Perry GH, Dominy NJ, Claw KG, et al. Diet and the evolution of human amylase gene copy number variation. Nat Genet. 2007;39(10):1256-60.
  2. Fernández CI, Wiley AS. Rethinking the starch digestion hypothesis for AMY1 copy number variation in humans. Am J Phys Anthropol. 2017;163(4):645-657.
  3. Carpenter D, Dhar S, Mitchell LM, et al. Obesity, starch digestion and amylase: association between copy number variants at human salivary (AMY1) and pancreatic (AMY2) amylase genes. Hum Mol Genet. 2015;24(12):3472-80.
  4. Mandel AL, Peyrot des gachons C, Plank KL, Alarcon S, Breslin PA. Individual differences in AMY1 gene copy number, salivary α-amylase levels, and the perception of oral starch. PLoS ONE. 2010;5(10):e13352.
  5. O'bleness M, Searles VB, Varki A, Gagneux P, Sikela JM. Evolution of genetic and genomic features unique to the human lineage. Nat Rev Genet. 2012;13(12):853-66.
  6. Parks BW, Nam E, Org E, et al. Genetic control of obesity and gut microbiota composition in response to high-fat, high-sucrose diet in mice. Cell Metab. 2013;17(1):141-52.
  7. Mejía-benítez MA, Bonnefond A, Yengo L, et al. Beneficial effect of a high number of copies of salivary amylase AMY1 gene on obesity risk in Mexican children. Diabetologia. 2015;58(2):290-4.
  8. Falchi M, El-sayed moustafa JS, Takousis P, et al. Low copy number of the salivary amylase gene predisposes to obesity. Nat Genet. 2014;46(5):492-7.
  9. Marcovecchio ML, Florio R, Verginelli F, et al. Low AMY1 Gene Copy Number Is Associated with Increased Body Mass Index in Prepubertal Boys. PLoS ONE. 2016;11(5):e0154961.
  10. Rukh G, Ericson U, Andersson-assarsson J, Orho-melander M, Sonestedt E. Dietary starch intake modifies the relation between copy number variation in the salivary amylase gene and BMI. Am J Clin Nutr. 2017;106(1):256-262.
  11. Luca F, Perry GH, Di rienzo A. Evolutionary adaptations to dietary changes. Annu Rev Nutr. 2010;30:291-314.

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