Are B vitamins stored in the organs in their Coenzymated forms?

[Bluelude1]

If you were to eat organ meats for their B-vitamin content would you be consuming it in its coenzymated form?

Using B2 as an example, would it be stored as riboflavin or FAD/FMN in an organ like the liver?

 

[Hip]

Water-soluble vitamins like the B vitamins and vitamin C are not stored in the body. Excess amounts of these vitamins are expelled in the urine.

 

[Bluelude1]

Water-soluble vitamins like the B vitamins and vitamin C are not stored in the body. Excess amounts of these vitamins are expelled in the urine.

They may not store like a fat soluble vitamin, but there would have to be some form of storage or organ meats wouldn't be a rich source of them.

 

[Hip]

They may not store like a fat soluble vitamin, but there would have to be some form of storage or organ meats wouldn't be a rich source of them.

Good point. Well I guess there might be limited storage in some organs. I found this document that details how much of each vitamin is stored in body; but it does not indicate the mechanism of storage.

 

[Bluelude1]

It's definitely a nuanced question, but we know in the case of B2 that the liver phosphorylates it before it can be utilized by the body. The document you found and everywhere else refer to it in its riboflavin form.

Maybe someone will know the answer. I might actually need to ask in the B12 forum due to the inherent similarities.

 

[alicec]

B2 and B6 within cells - ie in the organs you are consuming - would be predominantly in the phosphorylated form.

The whole point of phosphorylation is to keep the cofactors where they are needed and not let them leak out of cells - the phosphorylated forms don't cross cell membranes.

So in the digestive tract the phosphate group is clipped off to allow the vitamins to be taken up into cells. Once the vitamins are where they are needed, the phosphate group is added back to keep them there.

B12 is different - it is not phosphorylated. The different forms found in food are processed after they are taken up into cells (after going through a complex interaction with protein carriers and receptors).

 

[Hip]

Is there any particular reason you ask this question, @Bluelude1?

 

[Bluelude1]

Is there any particular reason you ask this question, @Bluelude1?

I am trying to understand which forms would be sourced from organs like the liver. There are a variety of different forms, but I've repeatedly seen a pattern where the animal organ forms are the most readily assimilated. For example this is seen in beta-Carotene vs vitamin A sourced from fish liver which is FAR more effectively assimilated, which is why its virtually impossible to overdose from vitamin A sourced directly from plants.

Adenosylcobalamin is the form of B12 we store in our liver, but we try to supplement with other forms.

I don't fully understand it all yet, but I am trying to.

 

[TigerLilea]

Does this answer your question, @Bluelude1 ?

Vitamin B12 consists of a class of chemically related compounds (vitamers), all of which show pharmacological activity. It contains the biochemically rare element cobalt (chemical symbol Co) positioned in the center of a planar tetra-pyrrole ring called a corrin ring. The vitamer is produced by bacteria as hydroxocobalamin, but conversion between different forms of the vitamin occurs in the body after consumption.

 

[Hip]

If you are thinking in terms of trying to ensure vitamin availability, then some people trying supplementing with the active form of the B vitamins. The vitamins that you normally find in supplements and in foods are the non-active form, which means they have to first be converted into the active form in the body in order to function.

Sometimes there is concern that the body may not be adequately converting these vitamins to the active form, which is why people may experiment with taking active form vitamins.

For example, pyridoxal-5-phosphate is the active form of vitamin B6, and riboflavin-5′-phosphate is the active form of vitamin B2.

 

[Bluelude1]

If you are thinking in terms of trying to ensure vitamin availability, then some people trying supplementing with the active form of the B vitamins. The vitamins that you normally find in supplements and in foods are the non-active form, which means they have to first be converted into the active form in the body in order to function.

Sometimes there is concern that the body may not be adequately converting these vitamins to the active form, which is why people may experiment with taking active form vitamins.

For example, pyridoxal-5-phosphate is the active form of vitamin B6, and riboflavin-5′-phosphate is the active form of vitamin B2.

That's essentially what I am getting at. Just trying to understand if that's how the organs are storing them...and it appears to be the case.

Where are the inactive forms in nature most commonly found outside of yeast....plants?

 

[alicec]

I am trying to understand which forms would be sourced from organs like the liver. There are a variety of different forms, but I've repeatedly seen a pattern where the animal organ forms are the most readily assimilated. For example this is seen in beta-Carotene vs vitamin A sourced from fish liver which is FAR more effectively assimilated, which is why its virtually impossible to overdose from vitamin A sourced directly from plants.

Adenosylcobalamin is the form of B12 we store in our liver, but we try to supplement with other forms.

I don't fully understand it all yet, but I am trying to.

By virtue of the role the liver plays in the body, it is a rich repository of stored co-factors which are predominantly in the active form used in the body.

What happens to these different forms when we eat the liver varies - there is no universal principle because co-factors become active by different mechanisms.

With the phosphorylated B vitamins (B1, B2, B6) the phosphate group is clipped off in the intestine to enable the base vitamins to be absorbed into the body. The phosphate group is put back once inside the cell.

Note this applies to supplemental vitamins just as much as it does to those in liver. I have seen one small study on B6 that does suggest that there might be an alternative uptake mechanism that allows some of the phosphorylated vitamin to be absorbed directly (likely to be some kind of endocytosis), so perhaps this could be significant when large doses of supplemental vitamins are taken and might explain why some people report different responses to the active and inactive forms.

But for the most part, supplements of the phosphorylated B vitamins are processed in the gut before absorption.

Different forms of B12 are taken up into cells and then processed in a very complex manner. Here is a post discussing these pathways and the question of different forms of supplemental B12.

All forms are first processed inside the cell and the upper axial ligand (methyl, adenosyl etc) is removed; the methyl and adenosyl forms are re-made as needed. But as I note in the post, there is a small amount of direct diffusion that is undefined and again may be important when high doses of supplemental vitamins are taken. This might explain why some report different responses to different forms.

In contrast to these B vitamins, pre-formed vit A is taken up and used as is.

 

[Bluelude1]

Wow alicec,

You're a wealth of knowledge. So the B vitamins will be dephosphorylated prior to transport to the liver where the liver will phosphorylate them as needed ...correct?

So FAD -> gets converted to riboflavin -> absorbed in the gut -> rephosphorylated again in the liver​

Any idea where the inactive forms like thiamine and riboflavin are most commonly found in nature outside of yeast?

 

[alicec]

So the B vitamins will be dephosphorylated prior to transport to the liver where the liver will phosphorylate them as needed ...correct?

Not just the liver - all cells.

Any idea where the inactive forms like thiamine and riboflavin are most commonly found in nature outside of yeast?

As far as I'm aware, phosphorylated forms predominate in all foods whether of plant or human origin. Plants after all use the same form of active co-factors as animals - as does yeast.

 

[Bluelude1]

As far as I'm aware, phosphorylated forms predominate in all foods whether of plant or human origin. Plants after all use the same form of active co-factors as animals - as does yeast.

I know this is going to sound ignorant, but if the active b vitamins become dephosphorylated prior to absorption in the gut rendering then effectively the same as the inactive forms, why is the dosing so different?

For example 50mg P5P is considered equivalent to 250mg Pyridoxine hydrochloride.

 

[alicec]

For example 50mg P5P is considered equivalent to 250mg Pyridoxine hydrochloride.

I don't know what that claim is based on.

 

[Bluelude1]

I don't know what that claim is based on.

I'd have to the find the source info, but it's represented in available dosing as well.

The highest dose P5P you can commonly purchase is 100mg where as 500mg is the highest dose available in Pyridoxine hydrochloride.