From The Desk Of Clarence Bass
“We provide evidence that cooked starch, a source of preformed glucose, greatly increased energy availability to human tissues with high glucose demands, such as the brain, red blood cells, and the developing fetus.” The Importance of Dietary Carbohydrate in Human Evolution by Karen Hardy et al, The Quarterly Review of Biology (September 2015)
Starchy Carbs: The Missing Link in the Paleo Diet—Big Brains Need Grains
See Below for Reader's Challenge, Clarence's Reply, & Professor's Perspective
It appears that starchy carbohydrates have had an important place in human evolution. An international team of scientists has made a powerful case that dietary carbohydrates were essential to development of the big brain that makes us human.
I was onboard long before I learned about the evolutionary connection.
I’m measuring out the six whole grains used in my “Old Reliable”
Except for a brief period in my early days as a competitive bodybuilder, carbohydrates have always been a key component of my diet. In my first book RIPPED, I recounted that I couldn’t think or train properly without carbohydrates. That’s why I abandoned the low carb diet and never went back.
In my commentary on Professor Art De Vany’s book The New Evolution Diet, I wrote, “Art and I avoid refined carbohydrates—but part company on intact grains.” De Vany wrote that we are not genetically equipped to process grains, in any form. I respectfully demurred.
I challenged the premise of the book Grain Brain by Neurologist David Perlmutter that carbs, even healthy carbs such as whole grains and fruit, are silently killing our brain. http://www.cbass.com/carbs_brain.htm
AND NOW we have evidence that Paleo diet devotees are on shaky ground in claiming that our Stone Age ancestors didn’t consume starchy carbs. Karen Hardy and her team, writing in The Quarterly Review of Biology (September 2015), concluded that starchy carbs were essential to the development of the human brain. Among other observations, they pointed out that the human brain (then and now) uses up to 25% of the body’s energy requirement and up to 60% of the body’s blood glucose. While synthesis of glucose from other sources is possible, it is not the most efficient way, and these glucose demands are unlikely to be met on a low carb diet.
Paleo Diet Dos and Don’ts
In practice, the contemporary Paleo diet calls for eating grass-fed meats, fish and seafood, fresh fruits and vegetables, eggs, nuts, and seeds—and avoiding cereal grains, legumes, dairy products, potatoes, refined vegetable oils, processed foods, sugar and salt. While avoiding processed foods, sugar and salt, and eating fruits and vegetables are good ideas, avoiding cereal grains and legumes presents a problem. While it is possible to consume an adequate diet without those foods, it’s inconvenient and difficult.
Another problem is that the Paleo diet can lead to overconsumption of meat; for some, it becomes a license to eat your fill of meat—which also means eating fewer carbs. The main problem, however, is that it eliminates whole grains, which are the main source of starchy carbs for most people. Moreover, avoiding legumes (peas and beans) removes most complex carbohydrates. The end result is likely to be a low carb diet.
The Paleo diet is an attempt to eat like humans did in the Paleolithic period, which ended about 12,000 years ago. The new study by researchers from Spain, Australia, and the UK provides evidence that cooked starch played an important role in human evolution. Karen Hardy et al argued that “digestible carbohydrates were…necessary to accommodate the increased metabolic demands of a growing brain.”
Big brains needed lots of starchy carbs then and need them now.
Let’s drill down into the study.
Rethinking the Paleo Diet
The global increase in obesity and diet-related diseases has ramped up interest in our ancestral diet. Surprisingly, there is little clear agreement on the make-up of the Paleolithic diet. “It is clear,” the researchers wrote in introducing their study, “that…our physiology should be optimized to the diet that we have experienced during our evolutionary past.” The increase in brain size, which began around 2 million years ago and accelerated until about 12,000 years ago, is thought to be directly linked to alteration in diet.
(Paleo diet proponents are correct on that point. They are also correct that the rise of agriculture brought with it health problems, according to Zack S. Conrad, a doctoral candidate at Tufts University’s Friedman School of Nutrition and Policy, who studies such matters. “But that isn’t because grains are bad for you; it was because the change was so abrupt,” he explained in the Tufts University’s Health & Nutrition Letter (July 2015). “People switched to eating almost only cereal grains, which resulted in severe micronutrient deficiencies, many of which are evident in skeletal remains,” he continued. Over time diets became more diversified and the problem was resolved.)
The transition to a predominantly meat based diet has been considered to be the major driver of the increase in brain size and other evolutionary changes. The Hardy team argues that carbohydrates were also essential. A fortunate combination of events made that possible. The widespread availability of cooking coincided with the emergence of digestive enzymes which released the energy-yielding potential of starches. Cooking softened starch-rich plant foods and the digestive enzymes made them available to fuel the development of the human prototype. The combination also reduced chewing time allowing Paleo man more time to use and develop his growing brain. There are more details, but that series of events led the researchers to conclude that starchy carbohydrates were an important part of the Paleo diet.
The researchers summarized their breakthrough findings as follows:
We propose that plant foods containing high quantities of starch were essential for the evolution of the human phenotype during the Pleistocene. Although previous studies have highlighted a stone tool-mediated shift from primarily plant-based to primarily meat-based diets as critical in the development of the brain and other human traits, we argue that digestible carbohydrates were also necessary to accommodate the increased metabolic demands of a growing brain. Furthermore, we acknowledge the adaptive role cooking played in improving the digestibility and palatability of key carbohydrates. We provide evidence that cooked starch, a source of preformed glucose, greatly increased energy availability to human tissues with high glucose demands, such as the brain, red blood cells, and the developing fetus. We also highlight the auxiliary role copy number variation in the salivary amylase genes may have played in increasing the importance of starch in human evolution following the origins of cooking. Salivary amylases are largely ineffective on raw crystalline starch, but cooking substantially increases both their energy-yielding potential and glycemia. Although uncertainties remain regarding the antiquity of cooking and the origins of salivary amylase gene copy number variation, the hypothesis we present makes a testable prediction that these events are correlated.
Although it is difficulty to decipher what happened eons ago, Hardy et al have provided convincing evidence and support for the inclusion of starchy carbohydrates in our ancestral diet. Paleo diet enthusiasts may want to consider making room on their menu for whole grains, legumes, and perhaps intact potatoes.
The Ancestral Diet
You may be wondering, as I was, what our ancient ancestors ate. Where did they get their starchy carbs? Big brains came before farming, so we can eliminate Cheerios and Wheaties.
Paleo man is believed to have eaten starch-rich roots and tubers. “Starch constitutes up to 80% of the dry weight of edible roots and tubers,” Hardy et al explained; “if left undisturbed in the ground, they remain stable and can be harvested as needed over a period of months…[They] can also be dried to increase durability and portability, and have been proposed as important foods for early hominins.”
Interestingly, these starch-rich foods may have been eaten more often than meat. It was hard work finding and killing animals and success was far from assured. “Although meat may have been a preferred food, the energy expenditure required to obtain it may have been far greater than that used for collecting tubers from a reliable source,” the researchers wrote.
It has also been suggested that postmenopausal females may have done most of the foraging to “enable younger female relatives to reproduce more frequently.” Food sourcing may have been a matter of status as well as practicality.
Cooking, of course, made both meat and starch-rich plant foods more palatable and digestible. As we have seen, both were apparently key components in the rise of humankind.
* * *
Carol and I will happily continue to include whole grains, legumes, and occasionally potatoes in our diet. We eat the potatoes whole, skin and all, combined with foods containing protein and fat to slow digestion.
What’s new is that the Hardy study reinforces our eating style—and gives Paleo diet proponents something else to think about.
have it much easier than our ancient ancestors. This photo taken by
Laszlo Bencze in our kitchen
January 1, 2016
Reader's Challenge & Clarence's Reply
Most doctors and
nutritionists will tell you that the problem is refined grains and not
whole grains. That's because whole grains are nutrient packed with
fiber, B vitamins, antioxidants, vitamin E and protein. Refined grains
on the other hand are milled and missing parts of their kernel thereby
reducing their nutritional quality. Whole grains are also more filling,
digest more slowly, and keep you satisfied longer.
Most people do best on a balanced diet. Extreme diets--high or low anything--are untenable for most people.
I believe that most authorities would consider 100 to 200 grams of carbohydrate relatively low, especially for an active person.
For an interesting--and
surprising--discussion of the ideal starch intake see
The Paleo thing is
fascinating. I have read a lot of the supposed research and it is a bit
full of magical thinking as you politely alluded. The anthropologic data
is far more controversial than Dr. Cordain and his protégé Robb Wolf
would have you believe.
Their genetic cousins in Siberia who eat mostly potatoes and coarse whole grains live much longer....the point is: tradition and ancestry are not necessarily the gold standards.
The Paleo conceit is appealing in a complex world of too many choices.
Human evolution favors behaviors that increase healthy breeding,
fertility, survival of children. There is little utility in members of
the tribe living to be be 100. Most diet and diet related behavioral
traits developed via evolution have little application to longevity.
Eating to stay healthy for a long time is a recent interest of humans
and still has little evolutionary desirability. Consequently, we are
probably better off examining groups of humans who luckily seem to live
long, and/or examining scientific studies to figure out how best to beat
the evolutionary curve.
Professor Wade Smith,
MD, Orthopedic Surgery, University of Colorado School of Medicine
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