How do we now if LOW conversion of ALA to DHA and beta carotene to retinol means POOR conversion... Couldn't it be optimal conversion? I have always beens suspicious of this, and there seems to be more and more evidence that having a proper ratio of vitamins is what is important, not the amount (ex. certain vitamins compete with one another- A and D).
I have always been curious about this, because it seems like consuming the plant forms of certain vitamins would be the SAFEST means of getting them and then allowing our bodies to convert what is necessary dictated by the rest of diet and the vitamin ratios in it. FOr instance assuming ceteris paribus, if Bradly eats 5g of ALA and converted 2 of it to DHA, and Audrey eats 8g of ALA and converts 2-y of it to ALA, they'll come out equal. And, ceteris paribus again, if Bradly eats 100mg of beta carotene and Audrey eats 200g of beta carotene, Brad may convert 50mg to retinal and Audrey converts 50mg-z of it retinol.
In other words, we insert the Brad and Audrey "only" converts x amount of plant vitamin to the animal form because it is not equivalent ex-poste (i.e. plant version is not converted to animal version on a 1-to-1 basis). However, this does not by any means imply it's not fully efficient or not optimal, it just means it's not 1-to-1. I haven't seen any evidence that it by necessity means it is not optimal. I'm sure there are perfectly healthy indigenous cultures who actually eat zero seafood, and yet have somehow survived healthily for thousands of years.
I hope I have explained myself adequately in a variety of ways so everyone gets it if they did not the first time. So, why do we assume that not 1-to-1 conversions of plant vitamin forms to animal vitamin forms means that we're "poor converters?" Maybe optimal is not 1-to-1 and is less than that and different for everyone based on the diet.**
For practical purposes, it does seem SAFER to consume plant vitamins and let our bodies determine the specific amounts and RATIOS that need to be converted over to animal form. Seems like a built in protection mechanism. This especially seems so since we are not carnivorous beings, and have things like a taste for sweet foods can develop toxicity from certain amounts of animal forms (retinol, for instance).
asked byforeveryoung (14952)
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on September 06, 2012
at 02:16 PM
From my chemist point of view, our bodies don't particularly like to keep around highly reactive things. DHA/EPA is a good example. They are less stable (thus more reactive), our bodies don't want a lot of these around, so it makes sense that conversion from ALA to DHA/EPA is on an as-needed basis. Retinol is toxic in high doses, so again it makes sense that conversion from beta-carotene is low to prevent toxicity problems.
The conversion is likely very dependent on a host of other factors. An important one being vitamin A status. If vitamin A sufficient, relatively little vitamin A is needed, thus conversion will be low. A diet rich in retinol will down-regulate enzymes that convert beta-carotene to retinol, so supplementing with beta-carotene will produce relatively little change in vitamin A status. If you eat a diet naturally low in retinol and high in beta-carotene, I'd venture a guess that your conversion is more efficient.