"The brain needs X grams of glucose per day" vs. "Ketones are a better fuel for your brain"

(Ben Davis) #1

I realize I’ve heard both of these from various keto resources. I commonly hear both of these. The first is:

“The brain needs X grams of glucose per day” - but it can all be supplied by the liver which can make glucose from protein via gluconeogenesis, thus no need to exogenous glucose taken with food.

However, I believe I have also heard many times “the brain runs more efficiently on ketones” and thus all the mental clarity and such.

So does the brain require glucose for fuel? Can its cells use ketones for fuel? I am confused.

(Banting & Yudkin & Atkins & Eadeses & Cordain & Taubes & Volek & Naiman & Bikman ) #2

Certain functions of the brain actually do require glucose. This is why gluconeogenesis is not a problem, but a useful feature.

Most of the brain can use either as a fuel, though. Dr. Mike has an extended discussion of starvation metabolism in this blog post, which he describes as the opposite end of the same stick from carbohydrate restricted dieting. You have a few physical processes that actually require glucose, and in the absence of dietary carbohydrate, you have a few pathways to convert protein, either dietary or lean body mass to glucose… good that we do.
https://proteinpower.com/drmike/2007/05/22/metabolism-and-ketosis/

(Ben Davis) #3

So there are some brain and kidney functions that require glucose, but most functions in these organs will run happily on ketones. The reason ketones are preferred is 1) the chemical process that produces them is overall a more efficient reaction via fatty acids than with glucose and 2) insulin doesn’t have to get involved to get glucose into the cells. Both forms of energy gets eventually converted to ATP, but ketones are more of a direct pathway versus glucose which, for most cells, induces more of an “emergency” process via insulin.

Sound right?

(A ham loving ham! - VA6KD) #4

I think of the brain as a dual-fuel device. Most of it can run on glucose or ketones interchangeably, while a small part of it needs glucose only (I think that number is only a couple or few 10’s of g’s of glucose per day to stave off unconsciousness and potentially brain death).

There was some studies last year that revealed the brain also produces minute quantities of fructose that is thought to be used in gene expression to alter brain function:

And