Component
Serum 25-hydroxyvitamin D3 concentration
Study-defined Serum 25-hydroxyvitamin D3 concentration. Read each linked record for species, exposure and endpoint.
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 acts on it
At day 28, the D2 arm showed a 13.2 nmol/L greater decline in 25(OH)D3 than placebo (95% CI9.7–16.6).
Experimental context and source evidence
- cross_nutrient
- false
- experimental_model
- Two randomized single-dose experiments; 100 volunteers, 97 analyzed
- exposure
- Study 1: one 50, 000 IU oral D2 dose versus placebo.
- limitations
- No direct enzyme-flux assay. Reciprocal fraction changes are not proof that D2 is toxic or that net total vitamin D falls.
- 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
- A large D2 dose lowered the measured D3-derived fraction in this experiment.
- primary_references
- [hammami2019] Vitamin-D2 treatment-associated decrease in 25(OH)D3 level is a reciprocal phenomenon: a randomized controlled trial. (2019). https://pubmed.ncbi.nlm.nih.gov/30658603/ DOI: 10.1186/s12902-019-0337-8
- tissue_or_cell_type
- Human circulating measurements
Vitamin D2 and D3: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1405–1416
AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Two randomized single-dose experiments; 100 volunteers, 97 analyzed · source_derived_draft · unverified_draft
### vd-hammami-d2-decreases-d3 At day 28, the D2 arm showed a 13.2 nmol/L greater decline in 25(OH)D3 than placebo (95% CI9.7–16.6). Condition category: normal nutrient_topic: Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. plain_language: A large D2 dose lowered the measured D3-derived fraction in this experiment. organism: Homo sapiens tissue_or_cell_type: Human circulating measurements experimental_model: Two randomized single-dose experiments; 100 volunteers, 97 analyzed limitations: No direct enzyme-flux assay. Reciprocal fraction changes are not proof that D2 is toxic or that net total vitamin D falls. exposure: Study 1: one 50, 000 IU oral D2 dose versus placebo. cross_nutrient: false [hammami2019] Vitamin-D2 treatment-associated decrease in 25(OH)D3 level is a reciprocal phenomenon: a randomized controlled trial. (2019). https://pubmed.ncbi.nlm.nih.gov/30658603/ DOI: 10.1186/s12902-019-0337-8
Complete structured claim and evidenceThe D2-only daily group did not show a change in serum 25(OH)D3 over the 11-week study.
Experimental context and source evidence
- cross_nutrient
- false
- experimental_model
- Double-blind placebo-controlled daily D2/D3/mixed trial; 68 adults represented in Fig.1; 11 weeks
- exposure
- Daily D2 1000 IU, D3 1000 IU, mixed 500+500 IU or placebo; 11 winter weeks.
- limitations
- Small groups and biochemical endpoints; authors reported comparable responses. Daily regimen differs from single-dose and food-fortification studies.
- 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
- A fall in the D3-derived fraction was not detected in every D2 regimen.
- primary_references
- [holick2008] Vitamin D2 is as effective as vitamin D3 in maintaining circulating concentrations of 25-hydroxyvitamin D. (2008). https://pubmed.ncbi.nlm.nih.gov/18089691/ DOI: 10.1210/jc.2007-2308
- tissue_or_cell_type
- Human circulating measurements
Vitamin D2 and D3: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 1288–1299
AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Double-blind placebo-controlled daily D2/D3/mixed trial; 68 adults represented in Fig.1; 11 weeks · source_derived_draft · unverified_draft
### vd-holick-d2-d3-fraction The D2-only daily group did not show a change in serum 25(OH)D3 over the 11-week study. Condition category: normal nutrient_topic: Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. plain_language: A fall in the D3-derived fraction was not detected in every D2 regimen. organism: Homo sapiens tissue_or_cell_type: Human circulating measurements experimental_model: Double-blind placebo-controlled daily D2/D3/mixed trial; 68 adults represented in Fig.1; 11 weeks limitations: Small groups and biochemical endpoints; authors reported comparable responses. Daily regimen differs from single-dose and food-fortification studies. exposure: Daily D2 1000 IU, D3 1000 IU, mixed 500+500 IU or placebo; 11 winter weeks. cross_nutrient: false [holick2008] Vitamin D2 is as effective as vitamin D3 in maintaining circulating concentrations of 25-hydroxyvitamin D. (2008). https://pubmed.ncbi.nlm.nih.gov/18089691/ DOI: 10.1210/jc.2007-2308
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.