The MYTH of requiring 130 grams of carbohydrate in the diet for the brain to function.
This is an outdated concept. We require far less carbohydrate in our diet because the liver will convert protein into glucose to adequately ‘run’ the brain. That’s how we survive in starvation.
I am told over and over that the brain is dependent on glucose and its dangerous to run low carb. This is the primary concern of doctors, medical students, dietitians, midwives and most people, but not biochemists.
Let’s explore some religion to break a myth.
Would God (in whatever form that is) make our most important organ, the brain, dependent on only one fuel source of glucose? Surely not.
On a foreign aid trip to Vanuatu I was looking through a 1996 textbook of physiology. There it all was on page 22 of a 1148 page textbook – in the Introduction to Physiology chapter. We are not even in the ‘fine print’ area!
Here’s some basic biochemistry.
The mitochondria is the engine of the cell. It will process a variety of fuel sources into Acetyl-CoA which then enters the Krebs cycle and converts into ATP – Adenosine Tri phosphate. ATP is found in all living tissue and provides energy for virtually all physiological processes. We are completely dependent on that ATP – it is life itself.
That mitochondria is like a teenager looking for food. It doesn’t care where the Acetyl CoA comes from, as long as it’s there.
Acetyl-CoA can be made from glucose, carbohydrate, ketone bodies (fatty acids) from fat, and amino acids from protein. The mitochondria is a hybrid engine and it will run efficiently on these different fuel sources.
Any cell that has mitochondrion will need Acetyl-CoA.
Every cell in the brain has mitochondria. As a result every brain cell can run along on ketones and low carb. That’s what happens if you skip a meal, fast overnight or longer. It’s all just perfectly designed to keep our brains functioning.
The brain will run very nicely on ketone bodies as the other fuel in hybrid engine bodies.
There is a transition phase, but brain function has been shown to improve on a Low Carbohydrate and Healthy Fat diet.
The only cells that are dependent fully on circulating (not ingested) glucose are the erythrocytes (red blood cells) and some cells in the kidney (thin cells of the loop of Henle) and the lens of the eye. These cells all lack mitochondria. No mitochondria means no hybrid engine.
These three cells are uniquely dependent on glucose that can be formed from a low carb diet or the liver by gluconeogenesis conversion of protein to glucose.
There is no absolute requirement for ingested carbohydrate and I cannot find any evidence from where that ‘magical’ or ‘imaginary’ figure of 130 grams has come from. I have been told that it was estimated at a conference once and has become urban folklore!
So when the next person says that the brain is dependent on glucose there is only one response…..
Do you really think God was stupid enough to make the brain, our most important organ to be dependent on one fuel source?
And certainly not on just glucose.
Dr. Gary Fettke