Da bih mozak funkcionirao optimalno trebali bih da jedemo veče količine UH. Pa da, nikako! Mnogo bolje deluje na ketonima i istovremeno kroz duži period ostaju uporabniji in zdaviji.
Published on April 18, 2011 by Emily Deans, M.D. in Evolutionary Psychiatry
What can be confusing is that there are a variety of theoretic advantages in the brain to a ketogenic diet, and we're not sure which ones are more important. A classic ketogenic diet had three major components which were thought to contribute to the anti-seizure effect. One, it was calorie restricted. Just calorie restricting epileptic monkeys (no matter what the macronutrient ratios) reduces seizure frequency (and increases longevity). Secondly, it was acidic, and the extra protons themselves could block proton-sensitive ion channels, or the ketone bodies or fats themselves could affect the neuron membranes, making them harder to excite. (For the biochem geeks out there, ketones or fats seem to affect ATP sensitive K+ ion channels, making hyperpolarization easier to maintain). Thirdly, it lowered glucose levels. And lower glucose is associated with a higher seizure threshold (that's good - one doesn't want to easily have a seizure!) and less neuronal excitability. Gads. Doesn't sound to me like glucose really is the preferred fuel for the brain after all.
And now let's really get down to the mitochondrial level. Mitochondria are the power plants of our cells, where all the energy is produced (as ATP). Now, when I was taught about biochemical fuel-burning, I was taught that glucose was "clean" and ketones were "smokey." That glucose was clearly the preferred fuel for our muscles for exercise and definitely the key fuel for the brain. Except here's the dirty little secret about glucose - when you look at the amount of garbage leftover in the mitochondria, it is actually less efficient to make ATP from glucose than it is to make ATP from ketone bodies! A more efficient energy supply makes it easier to restore membranes in the brain to their normal states after a depolarizing electrical energy spike occurs, and means that energy is produced with fewer destructive free radicals leftover.
What does it all mean? Well, in the brain, energy is everything. The brain needs a great deal of energy to keep all those membrane potentials maintained - to keep pushing sodium out of the cells and pulling potassium into the cells. In fact, the brain, which is only 2% of our body weight, uses 20% of our oxygen and 10% of our glucose stores just to keep running. (Some cells in our brain are actually too small (or have tendrils that are too small) to accommodate mitochondria (the power plants). In those places, we must use glucose itself (via glycolysis) to create ATP.) When we change the main fuel of the brain from glucose to ketones, we change amino acid handling. And that means we change the ratios of glutamate and GABA. The best responders to a ketogenic diet for epilepsy end up with the highest amount of GABA in the central nervous system.
One of the things the brain has to keep a tight rein on is the amount of glutamate hanging out in the synapse. Lots of glutamate in the synapse means brain injury, or seizures, or low level ongoing damaging excitotoxicity as you might see in depression. The brain is humming along, using energy like a madman. Even a little bit more efficient use of the energy makes it easier for the brain to pull the glutamate back into the cells. And that, my friends, is a good thing.
Let me put it this way. Breast milk is very high in fat. Newborns spend time in ketosis, and are therefore to some extent ketoadapted. Breast milk is also high in sugar, but babies' brains are so big they can handle a lot more sugar than us full-grown folks. Being ketoadapted means that babies can more easily turn ketone bodies into acetyl-coA and into myelin. Ketosis helps babies construct and grow their brains. (For those interested in nitty gritty details - babies are in mild ketosis, but very young babies seem to utilize lactate as a fuel in lieu of glucose also - and the utilization of lactate also promotes the same use of acetyl-CoA and gives the neonates some of the advantages of ketoadaptation without being in heavy ketosis.)
We know (more or less) what all this means for epilepsy (and babies!). We don't precisely know what it means for everyone else, at least brain-wise. Ketosis occurs with carbohydrate and protein restriction, MCT oil use, or fasting. Some people believe that being ketoadapted is the ideal - others will suggest that we can be more relaxed, and eat a mostly low sugar diet with a bit of intermittent fasting thrown in to give us periods of ketosis. (A caveat - I don't recommend intermittent fasting for anyone with an eating disorder without some extra support and consideration). Ketosis for the body means fat-burning (hip hip hooray!). For the brain, it means a lower seizure risk and a better environment for neuronal recovery and repair.
