Glucose is the quickest fuel for the brain and nervous system, though ketones can be preferred during ketosis.

“this pathway is the quickest source of fuel for the brain and the rest of the nervous system, it's the source of fuel for the brain and nervous system.”

“Now that we've established that glucose is the preferred source of fuel for the nervous system, I'd like to concentrate on a few of the other types of sugars that we ingest on a common basis, and the impact that those have on brain function and body function.”

“this is why our brains can use carbohydrates for a fuel but they can't use fat as a fuel it's too there's too much oxidative stress and our brains are really sensitive to that they can use ketones but that's separate”