You misunderstood what I said.
I quoted exactly what you said and ask for a link to support it so I can check it out.
Maybe you misunderstood what I said originally? I said gluconeogenesis evolved primarily to ensure the brain did not die of glucose starvation when intake of carbs was too low to provide the minimum glucose required. I said it did not evolve to provide the body generally with sufficient glucose to operate. That does not mean that other cells, organs that require some glucose to do whatever they do from utilizing some of the small amount of glucose synthesized by gluconeogenesis. Just that the brain has priority and will take it first. Whatever is left after the brain takes what it needs can certainly be used otherwise, for example by a sperm cell. But if it really requires a glucose molecule to penetrate an ovum’s shell, I’m sure the sperm cell doesn’t care where it came from.
Fructose, if I’m not mistaken.
Well, as a guess, if you are in need of explosive muscle performance, you are going to want some quick-burning glucose handy, right? But you are still going to want ketones to keep your heart and brain going, too, so I wouldn’t expect a drop in ketones under those circumstances. I wonder if cortisol doesn’t do something to the liver or pancreas to keep insulin from inhibiting ketogenesis.
When serum glucose rises because it’s in the diet, that is a completely different situation. In that case, we want to be storing fat, not burning it or turning it into ketones (i.e., partially burning it).
I wonder if this is actually true. And I’m only raising the question because Ben Bikman, who knows Cahill’s work, questions the notion—which I understand came from Cahill—that the brain needs 130 g of glucose a day. In fact, Bikman questions whether the brain needs any glucose at all.
@PaulL That would certainly be an interesting matter! I also wondered why if the brain could function getting 2/3 of it’s energy from β-hydroxybutyrate it couldn’t function on it at 100%.
Watch the video I linked above of Dr Ali. Maybe he’s just repeating Cahill. Still, I have a lot of respect for Ali and it would take some convincing to swing me over, even though I’m inclined to ‘wish it were so’. Aside from the brain what else would require glucose sufficiently to evolve gluconeogenesis? In another discussion someone claimed that gluconeogenesis was around long before humans and we inherited it for whatever reasons. No documentation offered.
Leptin in Initiation and Maintainance of Ketosis
Red blood cells?
When the glycerol backbone of the triglyceride is converted to glucose, this is also gluconeogenesis. It makes sense that the body would utilise this fuel source when mainly burning fat.
No sources, just enjoying thinking about these things
So, I misspoke. I got a high(er) reading on my ketonix, I hypothesized due to a higher fat intake the day before (only test once a day, in the mornings). I specifically ate more (saturated) fat yesterday (mainly in the form of sour cream/cream), and…my ketonix went back to a low level.
This is why I’ve given up theorizing about things. What I theorize would happen seems to be true…until it’s not. And then I don’t have a good explanation.
Heard a comment from Ben Bikman indicating he didn’t know what that would be, including the brain. Blood cells, maybe? (Shoot…just saw that @PaulL said the same thing.)
But something needs glucose, or else I wouldn’t have higher blood glucose every morning and every time I exercise. Just need to radioactively tag it to see where it goes…
Not keto, but I think a good general ref for glucose utilization under ‘normal’ dietary conditions - ie consumption of inordinate and unhealthy amounts of carbs. Interestingly, the only mentions of blood are in ref to other organs moving stuff around the system. The book can be searched so maybe a thorough exploration would turn up something.
Red blood corpuscles, for one. They are too small to contain mitochondria, so fatty-acid/ketone metabolism is not possible for them. I imagine the same is true of sperm cells, since they also lack mitochondria. (And thus we all inherit our mitochondrial DNA from our mothers.) There are certain other cells that supposedly also need glucose, not that I can recall them at the moment!
Dr. Georgia Ede has stated that certain regions of neurons in the brain are also too small to contain mitochondria and therefore need glucose. Unfortunately, Dr. Ede didn’t document that assertion, so I don’t know how true it is. It’s not that I doubt her, particularly, but that I have some conceptual problems with the notion and would like to learn more.
Cahill demonstrated that it was possible to drive glucose in his experimental subjects down to levels that would normally cause coma or death, but that they were fine because of the amount of ketones they were generating from fasting. So I’m not even sure why he put the figure for the brain’s glucose needs as high as 130 g/day.
@PaulL According to Dr Ali, the 130 gr per day glucose requirement is simply the minimum energy requirement by the brain, ie ~520 kcal. Up to 2/3 of that can come from ketones, so glucose can actually drop to sub-50 grams with the difference made up by ketones.
Now, that’s interesting. I didn’t know that. Do you have a link to Dr. Ali’s presentation? I’d love to read/watch it.
If you have a level of 100mg/dl, and five liters of blood, that’s about
100mg/dl x (10dl/l) x 5l = 5000mg or 5 grams of glucose.
Is your body really cranking out 26 times that per day, just to feed the brain via GNG? (And you’d need 27 times, to keep the blood sugar at 100.)
Maybe it’s true, as this found GNG at 171 g/day in a low carb (“isoenergetic H diet (H condition; 30%, 0%, and 70% of energy from protein, carbohydrate, and fat, respectively)”):
Seems to me there’s a benefit in EE to low carb:
I may have to think about that study…why is the body cranking out 171 g/d of glucose? Where is it going? Partly to replace glycogen, as they did “an exhaustive glycogen-lowering exercise test” beforehand, but still…
Ta! (How did I miss that?)
If you’re not in ketosis, then part of the glucose you’re eating feeds the brain’s energy requirement (min ~520 kcal/day) and gluconeogenesis is not even happening. If you’re in ketosis then β-Hydroxybutyrate supplies up to 2/3 of those calories depending on how much β-Hydroxybutyrate you’ve got floating around in your blood. So gluconeogenesis doesn’t really have to crank out all that much glucose.
I see that, but in that study, they were cranking out 171g/d of glucose. Why?
This could fit in with my theory that people who are exercising more would have higher blood glucose (overall), even while low carb, for reasons at least related to replacement of muscle glycogen.
So maybe it’s muscles that actually need glucose and drive glucose production?
I know Phinney and Volek have done studies on athletes where the low carb athletes have comparable glycogen as compared with the high carb athletes…I’ll have to find that study (or studies) and examine it in more detail, to see if they posit an explanation as to how that occurs.
This could be it! Gluconeogenesis is supposedly demand driven (some argue this), so once the brain gets all it wants, other organs/muscles in the queue get what they want.