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In what form is B12 stored in the liver?
- Thread starter Bluelude1
- Start date
In this thread 'methylB12 from foods' there is a list of foods with adenosyl-, methyl-, hydroxocobalamin content.
http://forums.phoenixrising.me/index.php?threads/methyl-b12-from-foods.43899/
Meat and liver have higher levels of adenosyl- and hydroxoB12. Methylcobalamin is found more in dairy products.
And in humans B12 is stored as adenosylcobalamin in the liver.
http://forums.phoenixrising.me/index.php?threads/methyl-b12-from-foods.43899/
Meat and liver have higher levels of adenosyl- and hydroxoB12. Methylcobalamin is found more in dairy products.
And in humans B12 is stored as adenosylcobalamin in the liver.
TigerLilea
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Isn't Vitamin B12 produced by bacteria?
veganmua
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They get B12 from the bacteria that produce it living on the grass they consume. But all cows raised for human consumption are supplemented with B12.
I've heard that the adenosylcobalamin stored in the liver is converted to methylcobalamin as the body needs it. Are there any cofactors that when insufficient can prevent this conversion in people?
TigerLilea
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Humans need intrinsic factor to absorb B12 in the small intestine.
Is intrinsic factor needed to absorb all forms of B12 including adenosylcobalamin ? Can it be bypassed via a sublingual lozenge?
TigerLilea
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I'm going to have to let someone more sciency answer that question for you. My knowledge of B12 is very limited.
I don't know the answer, but if anybody is researching B12, look for this: "functional B12 deficiency". Yo can have, as me, consistently higher than normal B12 as a result of the inability of the body to properly make use of it
NotThisGuy
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they are?
TigerLilea
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I'll have to check into that as I know when I get tested I am at the very high end of normal. I just assumed that I don't have a problem with B12.
veganmua
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Yup, B12 or just cobalt, which allows the cow's gut bacteria to produce the B12, which gets reabsorbed. Our gut bacteria can do this but as non-ruminants, our intestines are too short for it to get reabsorbed.
This is the cobalamin metabolism where you can see that adenosylcobalamin isn't converted directly to methylcobalamin. The methionine synthase reductase (MTRR gene) needs the cofactors NADPH, S-adenosylmethionine and FAD/FMN (vitamin B2 coenzyme) to convert cob(II)alamin to methylcobalamin.
If methylcobalamin donated its methylgroup and is converted to cob(I)alamin it can be 'recovered' back to methylcobalamin with copper, zinc and methylfolate.
"The total amount of vitamin B12 stored in body is about 2–5 mg in adults. Around 50% of this is stored in the liver. Approximately 0.1% of this is lost per day by secretions into the gut, as not all these secretions are reabsorbed. Bile is the main form of B12 excretion; most of the B12 secreted in the bile is recycled via enterohepatic circulation. Excess B12 beyond the blood's binding capacity is typically excreted in urine."
https://en.wikipedia.org/wiki/Vitamin_B12
The thing is, when I looked into the issue, I was unable to find the transportprotein that transports cobalamin from the liver back into the rest of the body, but maybe I missed something. Otherwhise, the body might not be able to access liver stores freely and would rely on 'enterohepatic circulation', excretion from the liver in small amounts into the bile and reabsorption in the gut with intrinsic factor.
Then you have the body stores in the cells but they are also adenosylcobalamin, and since there is no direct conversion from adenosyl- to methylcobalamin, I don't know wether that's always enough.
That's why I prefer hydroxocobalamin.
I'm pretty sure the intrinsic factor is needed to absorb all vitamin B12 forms, its just part of the basic vitamin B12 absorption. Sublingual forms are supposed to be able to bypass the intrinsic factor. There is some discussion wether they are as effective as cobalamin injections, you might have to try it out and see how well it works for you.