I though it would be interesting to summarize new and old knowledge about the minimum quantities of glucose the human body needs for its vital function. This is certainly an interesting subject, if there is, if your follow a Zero Carb Diet…
First, let’s say it right now, high and loud, as it is very important to understand the rest: human beings need ZERO carbohydrate in their diet to survive. Even if nutritionists, doctors and health authorities made “carbohydrates” part of the 3 groups of MACRONUTRIENTS our body requires everyday, alongside with proteins and fats, there is not one nutrition book published at this day that can support that say.
It is not because a few of our body cells rely only on glucose that we obligatory need to ingest 300 g of non-fiber carbohydrates per day as recommended…
Let’s give an example of cells that work only on glucose: red blood cells. Their main job is transportation of oxygen to all our body parts, oxygen that will, principally, be use to transform fat into energy by “oxidation”. So, to protect their precious cargo of oxygen, red blood cells needs to find another way to get energy for themselves aside “oxidation of fat”. And the only other source of energy production that do not require oxygen (anaerobic) is the use of glucose…
If all our body cells could rely only on glucose for mitochondrial energy production like red blood cells, do you know what would happen? We wouldn’t need to breathe, as oxygen would be useless to our body. BUT THIS IS NOT THE WAY NATURE HAS CREATED THE HUMAN BODY. If we are breathing creatures, if we crave oxygen, it is because we need principally it in our mitochondria to burn fat for energy.
The use of glucose in mitochondrial energy production is only limited to a few type of cells BECAUSE the said cells need to be protected from oxygen. Brain cells are a good example; nobody wants too much oxidation going on in their delicate brain cell network… Anyway, aside red blood cells and some of our brain cells + retinas cells and certain tissues in our gonad, the rest of the trillions cells of our body are programmed to burn FAT.
The “original misinterpretation” of the role of glucose as the best source of energy for our body came from the concept that glucose, not needing oxygen to produce energy, is a rapid source of the said energy for muscles; especially when the said muscle has to contract itself faster then the time it needs for one to breathe some air in…
Anyway, if we needed so much glucose for energy production, nature would have give us a much larger and efficient pancreas to handle all that needed sugar, AND, certainly, much smaller lung capacities because we would need less oxygen to burn fat…
But this is not the way humans were designed and not respecting “the rules” of our body is the road that leads directly to today’s epidemic of health problems.
So, yes, we need some glucose on a daily basis but not that much. AND OUR BODY CAN SAFELY PRODUCE ALL OF IT SO WE DO NOT HAVE TO WORRY TO FIND SOME IN OUR DIET.
Think about it. Is nature so stupid to create a human body needing the recommanded 300 g of carbohydrate per day and, at the same time, create the WINTER season??? You know, that season when no source of carbohydrates is available as most of them come from plants…
Now let’s see how efficient our body is in producing glucose.
Body needs for glucose are satisfied by gluconeogenesis, process using amino acids, ketones, the glycerol of fats + lactate and pyruvate recycled from glycogen use.
Interestingly, we know that under an adapted very low carb, adequate protein and high fat diet, one doesn’t even need amino acids from proteins to produce glucose. Meaning the “muscle wasting” theory is “out”; so much “out” that some folks can even GAIN muscle via protein sparing and increased insulin sensitivity.
Fat is a great fuel as long as you are adapted to burn it.
As for the brain needs for glucose, they go down seriously once you are adapted to burning fat and the derived ketones will answer up to 75 % of the brain needs. The liver produces most of the ketones but astrocytes cells in the brain can also generate ketones themselves, if needed. And if somebody argues with you on this point just say: if the brain would work only on glucose, why would it produce ketone???
Nowadays, most low-carb specialists agree our body needs to produce a minimum of 30 g glucose per day, as long as one is producing adquate ketones.
Which means the MORE one eats glucose, the LESS he will be in ketosis, the MORE his body will need glucose… and the more the said glucose can eventually damage his body.
Interestingly, 21.6% of the fat we burn (from diet or from your body reserve) will be transformed into glucose. This is a serious amount: if your Zero Carb diet contains a total of 150 g of fat per day, this means you get a 32.4 g of glucose right there.
And do not worry for your brain: aside being able to use glucose and ketones to run properly, it can also use LACTATE especially when you exercise.
Isn’t it amazing that the brain become more efficient and adaptive when someone is in ketosis… which can be translated as “when someone is on a Zero Carb diet?!!!!!!!!!”