How is protein digested/metabolized?

[Lumberg]

I've been thinking a lot about carbs in the diet and it leads me to think about proteins, too.

Fats are the topic of a whole other thread.

According to someone on here, I forget who, up to 58% of protein can be converted to glucose.

But how does your body decide how much to split into glucose? Is it determined by your blood sugar levels? Or just what is not needed to meet its needs for protein synthesis?

Also let's say you overeat a protein-rich meal, like say 3 whole chicken breasts. Does your body digest and absorb all of it, or if there's way more than necessary, does it allow some of the protein to pass though the digestive system unused?

And if your body can convert protein to glucose, what is the point of eating carbs?

Thanks diet gurus!

JC

 

[Lumberg]

bump for the diet gurus

 

[Lumberg]

where are all the diet gurus today?????

 

[plornive]

There are three processes I know of to utilize amino acids for something other than protein synthesis.

First is gluconeogenesis, the process of the liver converting amino acids to glucose. When blood sugar and insulin is low, cortisol is released to mobilize amino acids from lean tissue cells. These aminos (along with some glycerol from fat metabolism) are then converted by the liver to glucose. This is what would happen if you didn't eat enough carbohydrate. Or, if glucagon is high (due to high blood amino acid levels), the liver simply converts a portion of those aminos to glucose until glucagon levels decrease to normal. This is probably what would happen if you ate 3 servings of whey and blood sugar was normal or low. Chicken would be somewhat better because it digests more slowly.

Second is the direct conversion of amino acids to fat... I have been told this happens.

Third is the direct metabolism of amino acids by muscle.

 

[nclifter6feet6]

i believe its a proven FACT that only .8 -.9 grams of protien per pound of lean body mass can be utilized any more will just turn to glucose. ive heard this from lyle mcdonald and elsewhere.

people take 400+ grams of protien usually if they are on steroids because protien synthesis is higher. and also on the CRUM diet its a good way to fill you up more than eating carbs. protien especially meat is so filling..

also i hear that when the excess protien is turned into glucose(carbohydrate) its really like a "second rate" carbohydrate its not as good as a regular carbohydrate.

 

[Lumberg]

Hmmmmmm

There is a debate between eliminating carbs from the diet entirely (supposedly we humans "evolved" to consume this type of diet) or having some carbs.

Obviously simple sugars are bad for you whether you are a BBer or not--your body is simply not designed to handle a can of coke.

However mankind did not evolve to spend several hours a week in a gym, or take motorized conveyances to transport across great distances. So are you going to throw out the baby with the bathwater as far as carbs are concerened?

What I am trying to figure out is how big and cute is the baby?

And can the consumption of excess protein make up for the loss of the carb "baby"?


JC

 

[cockdezl]

I've been thinking a lot about carbs in the diet and it leads me to think about proteins, too.

Fats are the topic of a whole other thread.

According to someone on here, I forget who, up to 58% of protein can be converted to glucose.

But how does your body decide how much to split into glucose? Is it determined by your blood sugar levels? Or just what is not needed to meet its needs for protein synthesis?

The gluconeogenic aminos are convertable to glucose due to their molecular structures, and the 58% number comes from the fact that this is the percentage of aminos that have a convertable structure, the other 42% are convertable into keto acids.

As for how the body decides how much to convert is based more on situation. Under normal carb sufficient diets, the body only converts a small percentage into glucose, since the gluconeogenic enzymes are downregulated. But under situations of carb deprivation or strenuous exertion, these systems are upregulated to handle the demand for blood glucose.

Also let's say you overeat a protein-rich meal, like say 3 whole chicken breasts. Does your body digest and absorb all of it, or if there's way more than necessary, does it allow some of the protein to pass though the digestive system unused?

There is a portion of any food that is unabsorbed, not just proteinaceous foods. Microbial metabolism degrades a portion of all food.

As for how much protein can be digested at once, I have never been presented with any research to show that protein digestion and absorption is limited. I think that the human intestinal tract is sufficiently long enough to easily handle 100 grams of protein at a time, but this is just opinion.

And if your body can convert protein to glucose, what is the point of eating carbs?

Actually there is no survival need for carbohydrate (no essential carbohydrates). Carbohydrates are just damn tasty.

Thanks diet gurus!

JC [/B][/QUOTE]

 

[Lumberg]

That there is no survival need for carbs is something I suspected.

However as I said before there may be advantages to be gained from eating them. Just as there is no survival need to lift weights, but there is definitely a big advantage to be gained from that activity.

Lastly, I have heard that once you have induced gluconeogenesis (by limiting carbs) that your body is indiscriminate as far as where to get the aminos--it will just as soon break down muscle as the chicken you just ate. Any thoughts?

JC

 

[Lumberg]

Yeah but what about tubers and starchy vegetables? We should be able to handle that.

JC