aaron_c
Senior Member
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OK, I've been doing a bit of reading on the fat soluble vitamins and how and in what proportion one might take them. I hope yall will forgive some amount of repetition of what I have posted previously in this thread for the sake of putting it all together into one post:
Retinyl and retinol are the same thing.
1. Fat soluble vitamins (FSV) interact with each other for absorption. This study found that:
Significant competitive interactions for uptake were then elucidated among vitamin D, E and K, supporting the hypothesis of common absorption pathways. Vitamin A also significantly decreased the uptake of the other FSVs but, conversely, its uptake was not impaired by vitamins D and K and even promoted by vitamin E.
So D, E and K compete with each other. Vitamin A trumps all of them...probably. Does it depend on the form of vitamin A? See the next section for concerns about the vast majority of vitamin A that we take. [EDIT: Thank you for the article! It seems like they are using retinol, retinyl palmitate and retinyl acetate, all three of which, at least separately, appear to be cause for concern. This article that I am unable to access should explain how they are prepared.]
2. Vitamin A toxicity might vary widely: This paper that people from the Weston A Price Foundation like to cite found that:
3. Synthetic Vitamin A might be toxic: The Weston A Price Foundation (See the "Vitamin A Knavery section) has an involved rebuttal to a 1995 study that warned pregnant mothers about the dangers of vitamin A. Their conclusion (roughly) was that since people have ingested high doses of vitamin A in the form of animal livers ect for much of human history, seemingly with many benefits and none of the currently described ill effects, perhaps the dangers of vitamin A might be attributed to an ingestion of the single synthetic retinyl form, rather than "Natural vitamin A [which] occurs as a mixture of various isomers, aldehydes, esters, acids and alcohols."
4. An alternate explanation to why synthetic vitamin A might be toxic was given fairly informally by Dave, the owner of Green Pasture (which sells fermented cod liver oil). Obviously, he has a dog in this fight, but the idea is at least interesting to me. He passes on the suggestion of a physician he spoke with that fermentation might be a superior way to extract cod liver oil because enzymatic digestion will always convert organic compounds to the useful isomer, whereas heat or chemical processing will tend to break them down any which way. Perhaps some of the vitamin A toxicity could be from having the wrong isomer interfering with the proper use of vitamin A? Perhaps someone with a better grasp of organic chemistry can add their expertise.
5. Finally I found a little more on how Vitamins A and D work together. Perhaps a little too simply put, vitamin A complexed to its nuclear receptor can form a complex with vitamin d complexed to its nuclear receptor. This (presumably?) activates genes differently than the Vitamin A or D nuclear receptor complexes would activate separately.
So how much of each fat soluable vitamin should we take? I am not sure, but for now I will aim for moderately high doses of high-vitamin foods. I have ordered some fermented cod liver oil/high vitamin butter blend from www.greenpasture.org that is supposed to be something like what Weston A Price would recommend. I will try to remember to post the results, particularly if it seems to work.
Retinyl and retinol are the same thing.
1. Fat soluble vitamins (FSV) interact with each other for absorption. This study found that:
Significant competitive interactions for uptake were then elucidated among vitamin D, E and K, supporting the hypothesis of common absorption pathways. Vitamin A also significantly decreased the uptake of the other FSVs but, conversely, its uptake was not impaired by vitamins D and K and even promoted by vitamin E.
So D, E and K compete with each other. Vitamin A trumps all of them...probably. Does it depend on the form of vitamin A? See the next section for concerns about the vast majority of vitamin A that we take. [EDIT: Thank you for the article! It seems like they are using retinol, retinyl palmitate and retinyl acetate, all three of which, at least separately, appear to be cause for concern. This article that I am unable to access should explain how they are prepared.]
2. Vitamin A toxicity might vary widely: This paper that people from the Weston A Price Foundation like to cite found that:
...water-miscible, emulsified, and solid preparations of retinol are approximately 10 times as toxic as are oil-based retinol preparations.
Perhaps this is because the oil-based preparations allow the body to package and regulate the vitamin as it sees fit? Or are some of the naturalish water-miscible and emulsified versions (retinyl-palmitate, for instance) just more potent?
4. An alternate explanation to why synthetic vitamin A might be toxic was given fairly informally by Dave, the owner of Green Pasture (which sells fermented cod liver oil). Obviously, he has a dog in this fight, but the idea is at least interesting to me. He passes on the suggestion of a physician he spoke with that fermentation might be a superior way to extract cod liver oil because enzymatic digestion will always convert organic compounds to the useful isomer, whereas heat or chemical processing will tend to break them down any which way. Perhaps some of the vitamin A toxicity could be from having the wrong isomer interfering with the proper use of vitamin A? Perhaps someone with a better grasp of organic chemistry can add their expertise.
5. Finally I found a little more on how Vitamins A and D work together. Perhaps a little too simply put, vitamin A complexed to its nuclear receptor can form a complex with vitamin d complexed to its nuclear receptor. This (presumably?) activates genes differently than the Vitamin A or D nuclear receptor complexes would activate separately.
So how much of each fat soluable vitamin should we take? I am not sure, but for now I will aim for moderately high doses of high-vitamin foods. I have ordered some fermented cod liver oil/high vitamin butter blend from www.greenpasture.org that is supposed to be something like what Weston A Price would recommend. I will try to remember to post the results, particularly if it seems to work.
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