Component
Previtamin D3
UV-generated 7-dehydrocholesterol ring-opening product that thermally isomerizes to cholecalciferol.
2 recorded relationships. Experimental role, claim status and evidence remain attached to each record.
How nutrients influence it
Every nutrient with a recorded effect on this component, credited to the nutrient that acted rather than the chapter that recorded it. Open a nutrient to see the findings and the conditions they were measured under.
Other things that act on it
Enzymes, hormones, genes, and other components with a recorded effect. These are not nutrients, so they do not count toward the arrows above. Each finding names the chapter that recorded it.
How nutrients reach it in more than one step
Chains of two or more recorded steps that end here, grouped by the nutrient they start from. Each step is a separate finding, so a chain is a route a mechanism could take, not proof that it does.
Tracing routes…
What it does
Every recorded relationship this component is part of, grouped by its role. Plain wording comes first; the technical statement follows.
What it acts on
Skin-generated previtamin D3 underwent temperature-dependent isomerization to cholecalciferol, taking at least three days to complete under the reported conditions.
Experimental context and source evidence
- cross_nutrient
- false
- evidence_location
- Primary abstract; skin photochemistry and transport experiments.
- experimental_model
- Human skin photochemistry
- exposure
- Solar UV exposure followed by thermal conversion; at least 3 days for completion.
- limitations
- Completion time is experiment-specific and is not an absorption half-life.
- nutrient
- Vitamin D2 and D3 · Vitamin D2 and D3
- nutrient_topic
- Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin D2 and D3
- organism
- Homo sapiens
- plain_language
- The first skin photoproduct rearranges into vitamin D3.
- primary_references
- [holick1980] Photosynthesis of previtamin D3 in human skin and the physiologic consequences. (1980). https://pubmed.ncbi.nlm.nih.gov/6251551/ DOI: 10.1126/science.6251551
- tissue_or_cell_type
- skin
Vitamin D2 and D3: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 106–119
AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human skin photochemistry · source_derived_draft · unverified_draft
### vd-act-skin-thermal-isomerization Skin-generated previtamin D3 underwent temperature-dependent isomerization to cholecalciferol, taking at least three days to complete under the reported conditions. Condition category: normal nutrient_topic: Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. plain_language: The first skin photoproduct rearranges into vitamin D3. organism: Homo sapiens tissue_or_cell_type: skin experimental_model: Human skin photochemistry limitations: Completion time is experiment-specific and is not an absorption half-life. exposure: Solar UV exposure followed by thermal conversion; at least 3 days for completion. cross_nutrient: false evidence_location: Primary abstract; skin photochemistry and transport experiments. nutrient: Vitamin D2 and D3 [holick1980] Photosynthesis of previtamin D3 in human skin and the physiologic consequences. (1980). https://pubmed.ncbi.nlm.nih.gov/6251551/ DOI: 10.1126/science.6251551
Complete structured claim and evidence
What acts on it
Narrow-band ultraviolet irradiation converted cutaneous 7-dehydrocholesterol to previtamin D3; 295-300 nm was the most effective tested range.
Experimental context and source evidence
- cross_nutrient
- false
- evidence_location
- Primary abstract: optimal 295-300 nm; up to 65% conversion under 295-nm radiation.
- experimental_model
- Human skin irradiation with chemical product measurements
- exposure
- Narrow-band radiation; up to 65% conversion at 295 nm; fluence/time not in retrieved abstract.
- limitations
- Controlled photochemistry; no safe or universally effective sunlight duration follows.
- nutrient
- Vitamin D2 and D3 · Vitamin D2 and D3
- nutrient_topic
- Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin D2 and D3
- organism
- Homo sapiens
- plain_language
- UVB starts the skin pathway that makes vitamin D3.
- primary_references
- [maclaughlin1982] Spectral character of sunlight modulates photosynthesis of previtamin D3 and its photoisomers in human skin. (1982). https://pubmed.ncbi.nlm.nih.gov/6281884/ DOI: 10.1126/science.6281884
- tissue_or_cell_type
- skin
Vitamin D2 and D3: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 91–104
AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human skin irradiation with chemical product measurements · source_derived_draft · unverified_draft
### vd-act-skin-photoconversion Narrow-band ultraviolet irradiation converted cutaneous 7-dehydrocholesterol to previtamin D3; 295-300 nm was the most effective tested range. Condition category: normal nutrient_topic: Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. plain_language: UVB starts the skin pathway that makes vitamin D3. organism: Homo sapiens tissue_or_cell_type: skin experimental_model: Human skin irradiation with chemical product measurements limitations: Controlled photochemistry; no safe or universally effective sunlight duration follows. exposure: Narrow-band radiation; up to 65% conversion at 295 nm; fluence/time not in retrieved abstract. cross_nutrient: false evidence_location: Primary abstract: optimal 295-300 nm; up to 65% conversion under 295-nm radiation. nutrient: Vitamin D2 and D3 [maclaughlin1982] Spectral character of sunlight modulates photosynthesis of previtamin D3 and its photoisomers in human skin. (1982). https://pubmed.ncbi.nlm.nih.gov/6281884/ DOI: 10.1126/science.6281884
Complete structured claim and evidence
The events it takes part in
A mechanism often involves more than two components. These are the full events, with every participant and its role.
Situations it appears in
Low-supply and faulty-machinery situations recorded in the chapters where this component plays a part.
In the sources
Preserved passages that mention this component, quoted exactly. Open one to read it in context.
Open hypotheses
Proposed ideas that involve this component. They are labeled as hypotheses and do not change any recorded statement.
This is a research prototype built from draft material. It is not medical advice, and its statements still await verification against the original studies.