Vitamin A signaling
The only Place in Human Biology Where a Photon Directly Changes a molecule’s shape: light isomerises 11-cis-retinal to the all-trans form inside rhodopsin, and that shape change is the visual signal. Retinoic acid separately acts as a nuclear receptor ligand governing epithelial differentiation, which is why the same vitamin family treats acne. Retinoids are teratogenic and fat-soluble — the toxicity ceiling is real and close.
In depth
Vitamin a and its aldehyde — the chromophore of rhodopsin and a nuclear receptor ligand.
What drives it
Micronutrient status increases it.
Preformed retinol from animal sources and beta-carotene from plants. Carried by the intermediary-metabolism, micronutrient and clinical reviews. doi 10.3390/nu18132141 · PMC9967593
Liver increases it.
Hepatic stellate cells are the body's retinoid store. Carried by the intermediary-metabolism, micronutrient and clinical reviews. doi 10.3390/nu18132141 · PMC9967593
What it drives
It increases Vision.
Light isomerises 11-cis-retinal to all-trans inside rhodopsin, and that shape change is the visual signal. Carried by the intermediary-metabolism, micronutrient and clinical reviews. doi 10.3390/nu18132141 · PMC9967593
It increases Skin.
Retinoic acid is a nuclear receptor ligand governing epithelial differentiation. Carried by the intermediary-metabolism, micronutrient and clinical reviews. doi 10.3390/nu18132141 · PMC9967593
It reduces Clear skin.
The same receptor action is why this vitamin family treats acne. Carried by the intermediary-metabolism, micronutrient and clinical reviews. doi 10.3390/nu18132141 · PMC9967593
It increases Immune balance.
Retinoic acid directs T cell differentiation and mucosal immunity. Carried by the intermediary-metabolism, micronutrient and clinical reviews. doi 10.3390/nu18132141 · PMC9967593
Blends that modulate it
Each blend page names this pathway and carries the study behind its claim.
See it on the map
Open the causal map to follow this pathway upstream and downstream, arrow by arrow, each with its study.