Again, the important thing is ATP, and you can get it from either glucose or ketone bodies:
> In fact, the late George Cahill did an experiment many years ago (probably would never get IRB approval to do such an experiment today) to demonstrate how ketones can offset glucose in the brain. Subjects with very high levels of B-OHB (about 5-7 mM) were injected with insulin until glucose levels reached 1 mM (about 19 mg/dL)! A normal person would fall into a coma at glucose levels below about 40 mg/dL and die by the time blood glucose reached 1 mM. These subjects were completely asymptomatic and 100% neurologically functional.
no, you're both oversimplifying. the brain needs some glucose to sustain itself, a little bit, according to present day research. yes, it can principally function on ketones but not /exclusively/.
it is not controversial that the brain can survive long periods of time on principally ketones, but what has not yet been proven (for obvious ethical reasons) is whether or not the brain can sustain itself with absolutely no glucose whatsoever.
again, the ratios are key. i'm not contesting that ketones can be used as the principal fuel source, just that "the important thing is ATP" because the brain needs some glucose.
