Glucose Needs for Brain / Protein Needed to Prevent Muscle Loss on Low Carb Diet

T1DCarnivoreRunner
T1DCarnivoreRunner Posts: 11,502 Member
I wasn’t sure what to make the topic, but this is basically about zero carb and the need for glucose. Specifically, brain / nervous system needs for glucose because the brain cannot use fat for energy.

Background:

You can skip over this entire section to save time, but I’m including this because it might help provide some insight into my specific circumstances and why/how I came upon this. I’m a type 1 diabetic (I do not make insulin, nor do I make amylin). Also, I was a type 2 diabetic in the past, until I lost enough weight to no longer be insulin resistant. Someone with both type 1 and type 2 is sometimes called a “double diabetic.” My type 1 is controlled with an insulin pump using Apidra, Metformin, and Symlin on occasion. I also have Hashimoto’s Thyroiditis, which has been well managed with Synthroid. I also have been on Simvastatin for several years. I take vitamins / supplements including l-carnitine, fish oil, co-q 10, and a bunch of other stuff.

For more than 3 years, I have been tracking calories. Losses were always frustratingly slow and I was always hungry. I still am always hungry, though my appetite is not quite as grand as it was during the first year. I experienced challenges that nobody seemed to be able to understand, including myself.

A year ago, I started eating low carb. The logic was that it would help reduce BG fluctuations. I didn’t change calorie intake, but noticed an increased rate of loss. I didn’t expect this to happen because I had always been told it was about calories alone. This result was a happy surprise. I started at 150g per day and gradually decreased over time. I’ll admit having some carb creep days and a couple cheat days (i.e. no restrictions) during that time, but mostly stuck to the goal. Eventually, when I reached 20g-30g per day, it became difficult to lower carbs any further. Weight loss started to stall out. Diet was mostly meat, eggs, low carb vegetables, and peanuts / peanut butter. Most of the carbs came from peanuts, peanut butter, and low carb vegetables.

With weight loss stalled, I decided to try cutting just a little further to (near) zero carb.

Glucose needs for brain:

I discussed this zero carb plan to my endocrinologist, who pointed out unlike muscles, the brain can’t use fat for energy. For brain function, we need glucose. This point is sometimes made to suggest that low carb diets are harmful to brain function. Carbs create glucose, but they are not the only way to create glucose. Gluconeogenesis (GNG) is a process used to create glucose from protein. My endo corrected a prior misunderstanding I had where I had thought fat could also be converted back to glucose.

Like most wanting to lose weight, I would prefer that weight loss to come from fat and not from muscle. Even if I only used fat for energy aside from the nervous system (this is a big stretch), how much dietary protein would I need to consume to avoid use of muscle for GNG instead? To answer that, I figured I would first need to figure out how much glucose is needed and then calculate the protein required to reach that level of glucose after GNG.

From what I could find, my brain would normally need around 120g-130g of glucose per day (sources show from 110g-145g, but 120g-130g seems to be common and agreed upon… I’ll use 130g for now) (2,3). When in ketosis, however, ketones reduce the brain’s need for glucose proportionately (4). In the past when in dietary ketosis, blood ketones have been at least 1.2 mmol/l and sometimes higher (let’s use 2.5 as a typical and reasonable level). This results in a glucose reduction of 12% or 25%, depending on the level of ketones.

Some of these calculations will be rounded for efficiency.

Brain glucose needs (conservatively) 130g per day, reduced by 12% = 114g

Brain glucose needs (typical ketone level) 130g per day, reduced by 25% = 98g

As you can see, ketone levels can have a big impact on how much glucose is needed for brain function. The only source I found that disagrees with 120g-130g is (1), which mentions 130g for those in ketosis. I’m expecting that is an error since those in ketosis should be using less glucose (4).

*I can’t afford to test blood ketones as often as I would like, but have done so in the past in dietary ketosis and can continue to do so periodically. Being unable to test regularly prevents me from running new calculations daily and having updated and more precise daily protein goals.

Protein intake:

If I apply the 58% GNG efficiency factor and assume a 0g carb diet, how much protein do I need to eat to use dietary protein rather than muscle for brain fuel? Using brain glucose needs from above:

Conservatively: 114g / 0.58 = 197g of protein per day

Typical ketone level: 98g / 0.58 = 169g of protein per day

Assuming all carb intake goes to brain fuel, then each gram of net carbs reduces protein needs by 1.7g. However, if carb intake affects ketone production, then glucose needs increase. I’m not certain, but my guess is that the ketone increase from low carb is more than enough to make up for the GNG efficiency factor. Still, this is a lot of protein just to create the glucose needed for brain function. If I find that ketones are higher, I will not need as much protein… some of these ketone estimates may end up better than expected.

Disclaimer: I’m not a physician and I hold no medical certifications or qualifications.

Sources cited:
(1) https://proteinpower.com/drmike/2007/05/22/metabolism-and-ketosis/
(2) https://www.ncbi.nlm.nih.gov/books/NBK22436/
(3) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC292907/?page=1
(4) https://link.springer.com/chapter/10.1007/978-0-387-85998-9_45
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Replies

  • RalfLott
    RalfLott Posts: 5,036 Member
    edited March 2017
    @midwesterner85 -

    Many thanks!

    This is an important topic, especially for us confused T2Ds trying to figure out how much protein we dare eat per day, meal, etc.

    @baconslave
  • Sunny_Bunny_
    Sunny_Bunny_ Posts: 7,140 Member
    edited March 2017
    Dr Cahill and Dr Owen are the ones that first determined how much glucose the brain needs on a daily basis. But, just like everything else, their findings got misrepresented and everyone began to believe we needed 130g glucose a day.
    This article explains how the misrepresentation came about.

    "They found that the initial blood specimens, performed under the patients' usual dietary intake circumstances (high carbohydrate), demonstrated that the brain utilized about 130 grams of glucose per day.

    After six weeks of fasting, they found that the patients were fine mentally and emotionally (they tested them in a variety of ways) but their brain now utilized about 1/3 of the glucose compared with before. 2/3 of the brain's needs were now supplied by betahydroxybutyrate, the principle blood ketone body."

    So once fat adapted, you only need about 40-45g glucose a day.

    https://experiment.com/u/3f3C9g
  • RalfLott
    RalfLott Posts: 5,036 Member
    Dr Cahill and Dr Owen are the ones that first determined how much glucose the brain needs on a daily basis. But, just like everything else, their findings got misrepresented and everyone began to believe we needed 130g glucose a day.
    This article explains how the misrepresentation came about.

    "They found that the initial blood specimens, performed under the patients' usual dietary intake circumstances (high carbohydrate), demonstrated that the brain utilized about 130 grams of glucose per day.

    After six weeks of fasting, they found that the patients were fine mentally and emotionally (they tested them in a variety of ways) but their brain now utilized about 1/3 of the glucose compared with before. 2/3 of the brain's needs were now supplied by betahydroxybutyrate, the principle blood ketone body."

    So once fat adapted, you only need about 40-45g glucose a day.

    https://experiment.com/u/3f3C9g

    So... Around 90-110g protein if you're zero-carbing?
  • KeithF6250
    KeithF6250 Posts: 321 Member
    Very nice analysis. I'll add one more moving part complication. As your body mass decreases the amount of muscle needed to move that mass decreases. I formerly had to haul 225 pounds up a flight of stairs, now it's about 150. My knees thank me for it every day, my muscles seem to take the reduced workload without comment.
  • T1DCarnivoreRunner
    T1DCarnivoreRunner Posts: 11,502 Member
    Dr Cahill and Dr Owen are the ones that first determined how much glucose the brain needs on a daily basis. But, just like everything else, their findings got misrepresented and everyone began to believe we needed 130g glucose a day.
    This article explains how the misrepresentation came about.

    "They found that the initial blood specimens, performed under the patients' usual dietary intake circumstances (high carbohydrate), demonstrated that the brain utilized about 130 grams of glucose per day.

    After six weeks of fasting, they found that the patients were fine mentally and emotionally (they tested them in a variety of ways) but their brain now utilized about 1/3 of the glucose compared with before. 2/3 of the brain's needs were now supplied by betahydroxybutyrate, the principle blood ketone body."

    So once fat adapted, you only need about 40-45g glucose a day.

    https://experiment.com/u/3f3C9g

    Wouldn't that mean someone is at around 6.7 mmol/L blood ketones? That's the high end of dietary ketosis... not sure if I can get there. Either way, I figure I would err on the side of slightly too much protein in order to perhaps repair muscle from exercise (and provide a bit of glucose for muscles during exercise).

    The next thing I need to figure out is protein intake timing.
  • RalfLott
    RalfLott Posts: 5,036 Member
    Dr Cahill and Dr Owen are the ones that first determined how much glucose the brain needs on a daily basis. But, just like everything else, their findings got misrepresented and everyone began to believe we needed 130g glucose a day.
    This article explains how the misrepresentation came about.

    "They found that the initial blood specimens, performed under the patients' usual dietary intake circumstances (high carbohydrate), demonstrated that the brain utilized about 130 grams of glucose per day.

    After six weeks of fasting, they found that the patients were fine mentally and emotionally (they tested them in a variety of ways) but their brain now utilized about 1/3 of the glucose compared with before. 2/3 of the brain's needs were now supplied by betahydroxybutyrate, the principle blood ketone body."

    So once fat adapted, you only need about 40-45g glucose a day.

    https://experiment.com/u/3f3C9g

    Wouldn't that mean someone is at around 6.7 mmol/L blood ketones? That's the high end of dietary ketosis... not sure if I can get there. Either way, I figure I would err on the side of slightly too much protein in order to perhaps repair muscle from exercise (and provide a bit of glucose for muscles during exercise).

    The next thing I need to figure out is protein intake timing.

    Do we have a clear picture of what happens if we consume more protein than we need at a given time?
  • Sunny_Bunny_
    Sunny_Bunny_ Posts: 7,140 Member
    Dr Cahill and Dr Owen are the ones that first determined how much glucose the brain needs on a daily basis. But, just like everything else, their findings got misrepresented and everyone began to believe we needed 130g glucose a day.
    This article explains how the misrepresentation came about.

    "They found that the initial blood specimens, performed under the patients' usual dietary intake circumstances (high carbohydrate), demonstrated that the brain utilized about 130 grams of glucose per day.

    After six weeks of fasting, they found that the patients were fine mentally and emotionally (they tested them in a variety of ways) but their brain now utilized about 1/3 of the glucose compared with before. 2/3 of the brain's needs were now supplied by betahydroxybutyrate, the principle blood ketone body."

    So once fat adapted, you only need about 40-45g glucose a day.

    https://experiment.com/u/3f3C9g

    Wouldn't that mean someone is at around 6.7 mmol/L blood ketones? That's the high end of dietary ketosis... not sure if I can get there. Either way, I figure I would err on the side of slightly too much protein in order to perhaps repair muscle from exercise (and provide a bit of glucose for muscles during exercise).

    The next thing I need to figure out is protein intake timing.

    I don't know if blood ketones run that high just because the brain is using more.
    I eat zero carb with about 90g protein (when I have bothered to track it) and the few times I have tested blood ketones, it was generally around 1 to 1.5. My bg runs steadily between mid 80's to high 90's regardless of fasting or after meals. Again, when I have tested. I don't test on the regular. I'm completely out of blood ketone strips at the moment.
  • Sunny_Bunny_
    Sunny_Bunny_ Posts: 7,140 Member



    If I apply the 58% GNG efficiency factor and assume a 0g carb diet, how much protein do I need to eat to use dietary protein rather than muscle for brain fuel? Using brain glucose needs from above:


    I think the body uses "lean tissue" for GNG, not necessarily muscle. It can use excess skin, connective tissues that are now more than your smaller body needs for that purpose and why wouldn't it? It certainly makes more sense to catabolize unnecessary tissues before necessary ones.
  • T1DCarnivoreRunner
    T1DCarnivoreRunner Posts: 11,502 Member
    Dr Cahill and Dr Owen are the ones that first determined how much glucose the brain needs on a daily basis. But, just like everything else, their findings got misrepresented and everyone began to believe we needed 130g glucose a day.
    This article explains how the misrepresentation came about.

    "They found that the initial blood specimens, performed under the patients' usual dietary intake circumstances (high carbohydrate), demonstrated that the brain utilized about 130 grams of glucose per day.

    After six weeks of fasting, they found that the patients were fine mentally and emotionally (they tested them in a variety of ways) but their brain now utilized about 1/3 of the glucose compared with before. 2/3 of the brain's needs were now supplied by betahydroxybutyrate, the principle blood ketone body."

    So once fat adapted, you only need about 40-45g glucose a day.

    https://experiment.com/u/3f3C9g

    Wouldn't that mean someone is at around 6.7 mmol/L blood ketones? That's the high end of dietary ketosis... not sure if I can get there. Either way, I figure I would err on the side of slightly too much protein in order to perhaps repair muscle from exercise (and provide a bit of glucose for muscles during exercise).

    The next thing I need to figure out is protein intake timing.

    I don't know if blood ketones run that high just because the brain is using more.
    I eat zero carb with about 90g protein (when I have bothered to track it) and the few times I have tested blood ketones, it was generally around 1 to 1.5. My bg runs steadily between mid 80's to high 90's regardless of fasting or after meals. Again, when I have tested. I don't test on the regular. I'm completely out of blood ketone strips at the moment.

    I mean, based on 10% reduction per mmol, 67% (2/3) reduction in brain glucose needs would be achieved with ketones at 6.7.



    If I apply the 58% GNG efficiency factor and assume a 0g carb diet, how much protein do I need to eat to use dietary protein rather than muscle for brain fuel? Using brain glucose needs from above:


    I think the body uses "lean tissue" for GNG, not necessarily muscle. It can use excess skin, connective tissues that are now more than your smaller body needs for that purpose and why wouldn't it? It certainly makes more sense to catabolize unnecessary tissues before necessary ones.

    Good point, but I'm not sure how much that ends up being. My goal now is to conserve muscle, so assuming it all comes from muscle helps to ensure the calculated dietary protein needs are high enough.
    RalfLott wrote: »
    Dr Cahill and Dr Owen are the ones that first determined how much glucose the brain needs on a daily basis. But, just like everything else, their findings got misrepresented and everyone began to believe we needed 130g glucose a day.
    This article explains how the misrepresentation came about.

    "They found that the initial blood specimens, performed under the patients' usual dietary intake circumstances (high carbohydrate), demonstrated that the brain utilized about 130 grams of glucose per day.

    After six weeks of fasting, they found that the patients were fine mentally and emotionally (they tested them in a variety of ways) but their brain now utilized about 1/3 of the glucose compared with before. 2/3 of the brain's needs were now supplied by betahydroxybutyrate, the principle blood ketone body."

    So once fat adapted, you only need about 40-45g glucose a day.

    https://experiment.com/u/3f3C9g

    Wouldn't that mean someone is at around 6.7 mmol/L blood ketones? That's the high end of dietary ketosis... not sure if I can get there. Either way, I figure I would err on the side of slightly too much protein in order to perhaps repair muscle from exercise (and provide a bit of glucose for muscles during exercise).

    The next thing I need to figure out is protein intake timing.

    Do we have a clear picture of what happens if we consume more protein than we need at a given time?

    That's a good question that I should look into further. If it gets converted to glucose and not used, then the extra glucose will become fat. If it converts to muscle instead, then I win! So how can I manage that so I win? It's something else I have to figure out.
  • Gallowmere1984
    Gallowmere1984 Posts: 6,626 Member
    RalfLott wrote: »
    Dr Cahill and Dr Owen are the ones that first determined how much glucose the brain needs on a daily basis. But, just like everything else, their findings got misrepresented and everyone began to believe we needed 130g glucose a day.
    This article explains how the misrepresentation came about.

    "They found that the initial blood specimens, performed under the patients' usual dietary intake circumstances (high carbohydrate), demonstrated that the brain utilized about 130 grams of glucose per day.

    After six weeks of fasting, they found that the patients were fine mentally and emotionally (they tested them in a variety of ways) but their brain now utilized about 1/3 of the glucose compared with before. 2/3 of the brain's needs were now supplied by betahydroxybutyrate, the principle blood ketone body."

    So once fat adapted, you only need about 40-45g glucose a day.

    https://experiment.com/u/3f3C9g

    Wouldn't that mean someone is at around 6.7 mmol/L blood ketones? That's the high end of dietary ketosis... not sure if I can get there. Either way, I figure I would err on the side of slightly too much protein in order to perhaps repair muscle from exercise (and provide a bit of glucose for muscles during exercise).

    The next thing I need to figure out is protein intake timing.

    Do we have a clear picture of what happens if we consume more protein than we need at a given time?

    Nearly half of any ingested protein (can be more if consumption rate is high) just ends up getting deaminated in the liver (not converted to glucose) and oxidized for energy. The body has no storage for it outside of organs, skeletal muscle and connective tissues, and that stuff can only be synthesized but so fast.

    Honestly, I think comparing excess protein to alcohol would be more accurate than comparing it to carbs. Obviously, not the poison part, but how the body handles the excess amounts. The only real difference in the fate, is the fact that the body has literally no storage for alcohol calories, so they are metabolized and burned off with 100% efficiency, and as quickly as possible.
  • Gallowmere1984
    Gallowmere1984 Posts: 6,626 Member
    edited March 2017
    Also of note: the body has a preference order, or hierarchy if you will, for how it handles incoming macros. Essentially, it's storage capacity for a given macro is directly inverse to it's preference for metabolization.

    Alcohol has zero storage; it gets burned first, and is perfectly metabolized. Carbs are next, as their storage is limited by the liver and muscular glycogen capacity. Then protein, and finally fat, which essentially has an unlimited storage capacity, and requires less energy to store.

    Alcohol can't be stored, de novo lipogenesis isn't a typical fate for carbs (and is why "carbs make you fat" is completely incorrect in the most direct sense), and protein's deamination process is VERY costly from an energy perspective. Usually when someone gets fat from a caloric surplus, it's literally the fat that ends up making them fat, due to ease of storage, and the fact that storage capacity is essentially unlimited.

    Now, given how the body works, in that it's constantly turning over cells and cell contents (including fat cells), the macro composition only really has an effect when a "pure" macro diet is consumed. This is nearly impossible, unless one ate nothing but say vodka, isolated proteins, refined sugars, or drank straight oils. Other than that, the body's burn order is less relevant than the overall energy balance, but that's how it works, in a nutshell.

    It's why woman who are heavy alcohol drinkers tend to be underweight, while men end up overweight. Women don't tend to eat anything when on a bender. Men tend to shove in every godawful thing they can find. Zero storage for the alcohol, but it puts everything else on the back burner until it's gone.

    A pure protein diet will also likely never make someone fat, as the conversion processes are stupid expensive, metabolically speaking.
  • kpk54
    kpk54 Posts: 4,474 Member
    @midwesterner85, this Dr. Fung link may provide some insight (1 expert's opinion) into what happens regarding "too much protein". If I am interpreting Fung correctly too much protein turns to flab. Read at least the paragraph above the pic of the man with loose skin.

    https://intensivedietarymanagement.com/how-much-protein-is-excessive/
  • Gallowmere1984
    Gallowmere1984 Posts: 6,626 Member
    kpk54 wrote: »
    @midwesterner85, this Dr. Fung link may provide some insight (1 expert's opinion) into what happens regarding "too much protein". If I am interpreting Fung correctly too much protein turns to flab. Read at least the paragraph above the pic of the man with loose skin.

    https://intensivedietarymanagement.com/how-much-protein-is-excessive/

    Ugh, Fung is hopeless. Literally everything in his first sentence is wrong.

    Please, for the love of god, read something based on how the body actually works. Start here: http://www.bodyrecomposition.com/nutrition/excess-protein-and-fat-storage-qa.html/

    Then read his follow-up where people starting making a bunch of absurd claims about what he said, and he corrected them: http://www.bodyrecomposition.com/fat-loss/how-we-get-fat.html/
  • Gallowmere1984
    Gallowmere1984 Posts: 6,626 Member
    Oh, and if you want further proof, read this:
    https://jissn.biomedcentral.com/articles/10.1186/1550-2783-11-19

    The guys in that study were allowed to continue their normal training and diet, BUT one group added a shitload of protein isolates to their diet, and thus increased both protein and kcals. The result?
    "The HP group consumed significantly more protein and calories pre vs post (p < 0.05). Furthermore, the HP group consumed significantly more protein and calories than the CON (p < 0.05). The HP group consumed on average 307 ± 69 grams of protein compared to 138 ± 42 in the CON. When expressed per unit body weight, the HP group consumed 4.4 ± 0.8 g/kg/d of protein versus 1.8 ± 0.4 g/kg/d in the CON. There were no changes in training volume for either group. Moreover, there were no significant changes over time or between groups for body weight, fat mass, fat free mass, or percent body fat."

    Seriously, I don't mean to be crass, but Fung is so full of *kitten*, I don't know how he doesn't explode.
  • kpk54
    kpk54 Posts: 4,474 Member
    @Gallowmere1984 note Fung is not saying protein turns to or gets stored as fat but rather it remains as flab. There is a difference....
  • Gallowmere1984
    Gallowmere1984 Posts: 6,626 Member
    edited March 2017
    kpk54 wrote: »
    @Gallowmere1984 note Fung is not saying protein turns to or gets stored as fat but rather it remains as flab. There is a difference....

    That's not how it works. Fat cells contain triglyceride and water. That's all. And nothing "remains", given that all cells are regularly being turned over, emptied, refilled, replaced, etc. including fat cells. All of the fat you have right now is different fat than you had two months ago, whether you lost weight or not.

    So, if that in fact is what he's saying, I take back what I said about him being full of *kitten*. He's either a total idiot, or a blatant liar. There is no middle ground anymore.
  • KeithF6250
    KeithF6250 Posts: 321 Member
    @Gallowmere1984 Thanks for the links to the Body Recomposition site, there is a lot of interesting stuff there. I did find this article which addresses the question from the OP from a slightly different perspective.
    http://www.bodyrecomposition.com/nutrition/how-many-carbohydrates-do-you-need.html/
  • Gallowmere1984
    Gallowmere1984 Posts: 6,626 Member
    KeithF6250 wrote: »
    @Gallowmere1984 Thanks for the links to the Body Recomposition site, there is a lot of interesting stuff there. I did find this article which addresses the question from the OP from a slightly different perspective.
    http://www.bodyrecomposition.com/nutrition/how-many-carbohydrates-do-you-need.html/

    You're very welcome. Lyle is one of the most trusted, but often lesser known men in the nutrition game. He, along with Layne Norton are definitely the top tier of evidence based food science, and because science is less sexy than the hucksterish BS we've gotten used to, they're a bit more obscure.
  • KeithF6250
    KeithF6250 Posts: 321 Member
    I spent 2-3 hours reading on his site yesterday. He is geared toward weight loss and body building. I'm a 70 year old formerly fat T2 controlling BG with diet rather than diabetes meds so my needs are somewhat different than most of his clients but science is science. I always regard it as a good day when I learn something and I learned several things yesterday.
  • Gallowmere1984
    Gallowmere1984 Posts: 6,626 Member
    edited March 2017
    KeithF6250 wrote: »
    I spent 2-3 hours reading on his site yesterday. He is geared toward weight loss and body building. I'm a 70 year old formerly fat T2 controlling BG with diet rather than diabetes meds so my needs are somewhat different than most of his clients but science is science. I always regard it as a good day when I learn something and I learned several things yesterday.

    This is very true, but even sports nutrition is heavily rooted in the basics of biology, which is where a lot of his focus lies. Really, learning about metabolic pathways, the function of basic macro/micros (and their individual components) within the body, etc. could benefit anyone.

    It's the difference between seeing 20g protein from nuts or beans, and 20g protein from chicken or fish (or soy to compare apples to apples) and knowing there's a difference between the two, or just assuming that "protein is protein".

    It's the difference between assuming that walnuts are a proper source of PUFAs (they're way higher in w-6 than w-3) or realizing that fish oil is far superior.

    Hell, it's even the difference between assuming that saturated fat will give you cancer of the AIDS, and realizing that it does amazing things for cholesterol and testosterone production.