Dietary vitamin A (beta carotene) is not the active form of vitamin A (retinoic acid), it needs to be converted into the active form by the body’s enzymes. Once retinoic acid is formed, it can bind to the retinoic acid receptor and regulate gene expression.
Retinoid treatment bypasses these enzymes and directly activates retinoic acid receptor signaling. So, eating vitamin A in the form of beta carotene won’t directly increase retinoic acid receptor signaling because the rate-limiting step is the enzymes, but retinoid treatment will. This is also why you can’t overdose on vitamin A by eating carrots.
Does this meet your criteria for a good answer? If not I can explain in more detail.
Dietary vitamin A (beta carotene) is not the active form of vitamin A (retinoic acid), it needs to be converted into the active form by the body’s enzymes.
It is possible to eat the active form of vitamin A, for example through animal sources like liver.
When I said vitamin A, I meant vitamin A (not the compound in plants that can be lossily converted into vitamin A).
The highly active form of vitamin A is isotretinoin, which you can take orally. It has substantial side effects though, meaning it’s generally only used for severe (cystic) acne.
If you want to think of it as a kind of deficiency you can, but then only your skin is deficient in vitamin A (not the rest of your body).
Dietary vitamin A (beta carotene) is not the active form of vitamin A (retinoic acid), it needs to be converted into the active form by the body’s enzymes. Once retinoic acid is formed, it can bind to the retinoic acid receptor and regulate gene expression.
Retinoid treatment bypasses these enzymes and directly activates retinoic acid receptor signaling. So, eating vitamin A in the form of beta carotene won’t directly increase retinoic acid receptor signaling because the rate-limiting step is the enzymes, but retinoid treatment will. This is also why you can’t overdose on vitamin A by eating carrots.
Does this meet your criteria for a good answer? If not I can explain in more detail.
Hi, thanks for responding. You say:
It is possible to eat the active form of vitamin A, for example through animal sources like liver.
When I said vitamin A, I meant vitamin A (not the compound in plants that can be lossily converted into vitamin A).
So this doesn’t answer the question IMO
The highly active form of vitamin A is isotretinoin, which you can take orally. It has substantial side effects though, meaning it’s generally only used for severe (cystic) acne.
If you want to think of it as a kind of deficiency you can, but then only your skin is deficient in vitamin A (not the rest of your body).
How do we know?