Paul Jaminet's blog post 'Can there be a carbohydrate deficiency?' Dr. Rosedale's response.
i.e. Paul Jaminet's blog post 'Can there be a carbohydrate deficiency?' i.e. Is there a need for carbs?;
Paul Jaminet answers his question affirmatively by stating,
"The brain is the biggest determinant of glucose needs. While other primates need only about 7% of energy as glucose or ketones, humans need about 20%. Compared to other primates, humans have a 12% smaller liver. This means we can’t manufacture as much glucose from protein as animals can. Humans also have a 40% smaller gut. This means we can’t manufacture many short-chain fatty acids, which supply ketones or glucogenic substrates, from plant fiber.
So, while animals can meet their tiny glucose needs (5% of calories) in their big livers, humans may not be able to meet our big glucose needs (20-30% of calories) from our small livers. So any carbohydrate deficiency disease will strike humans only, not animals."
Though good thoughts, I must disagree with Paul conceptually and factually. The brain needing 20% glucose is only under conditions of insufficient adaptation to burning ketones. Basic metabolic textbooks talk about adaptation to carbohydrate "starvation" when the brain starts deriving the vast majority of its energy needs from ketones derived from fat metabolism. After several weeks of adaptation the brain can derive at least 80% of its energy needs from ketones. After a longer period of time it can derive more. Regardless, the remainder of the brain's energy needs can be met from gluconeogenesis using glycerol derived from the breakdown of triglycerides as substrate such that gluconeogenesis derived from amino acids is minimal to nonexistent, sparing lean mass. In fact, my patients who strictly adhered to my very low carbohydrate dietary recommendations generally increased lean mass without increasing exercise.
The size of the human liver has little to nothing to do with its metabolic abilities. Rather, it's adaptation to available nutrients and even more importantly its control by, and indeed its sensitivity to metabolic hormones such as insulin and leptin are much more important to its function. Eating 100 g of glucose forming carbohydrates daily is enough to sufficiently raise insulin to shut down ketone production by the liver resulting in the necessity to use glucose as fuel by the brain. As such, what Jaminet is recommending is a self-fulfilling prophecy; requiring the consumption of glucose forming carbohydrates such as potatoes and rice increases blood glucose and insulin enough to greatly reduce ketone production, necessitating the use of glucose by the brain. This is not good. I have talked decades about the change in brain function when it converts from glucose to primarily ketone use; it becomes much healthier. Studies are now pouring in on the connection between glucose and chronic brain diseases. Jaminet rightly mentions the benefit of increasing ketone use in epilepsy. Epilepsy is an extreme of an over excitable brain. Is it possible that a brain primarily burning ketones as its primary fuel may function better all of the time? I believe strongly that the answer to this is yes.
Further counterpoints to the need for carbs;
I have never seen a list of essential nutrients that included a single carbohydrate. This means, that as far as current science knows, a human being does not have to take a single gram of carbohydrate their entire life to maintain health. This is because it is well known that although there is a certain need for carbohydrates and sugars, the body can make what it needs from other sources, either triglycerides or proteins. If the body is using fat as its primary fuel, then it needs (much) less glucose. The glucose that is necessary (more for anaerobic red blood cells than the brain) can either come from glycerol from the breakdown of triglycerides or from glucogenic amino acids that would be much less desirable. Deriving glucose from amino acids from protein requires either the consumption of excess protein–not good (I have written much about this previously) or the breakdown of lean mass–obviously not good, but no choice if one can't eat i.e. while sleeping. So the real question becomes, not whether carbohydrates are needed, but what other sources will the body use as substrates to make the glucose that it needs while not necessitating oral consumption. By far, the best substrate for glucose manufacture is glycerol, but this is largely only available if one is oxidizing fatty acids from triglycerides, and this is not possible when one consumes glucose forming foods such as rice and potatoes thus raising insulin and leptin and shutting off fatty acid oxidation.