Improvement after a supplement is not the same as a comparative result
Start with the comparison. A before-and-after change alone cannot isolate the contribution of an ingredient.
Vitamin D
Selected research topic
Immune and respiratory health
Findings differ across measurements or study conditions. The results below keep them separate.
Some findings concern patients or people with a deficiency.
- Publications for this topic
- 18
- Human comparison publications
- 4
- Publications needing review
- 7
Findings in the studies
incidence of infection
- A better result than the comparison group was reported.Patient group · Single ingredient · 12 weeks
Measurement and study conditions
- Study type
- Randomized controlled trial: subjects were randomly assigned to groups for comparison.
- Study population
- Human participants · Patient group
- Ingredients tested
- Single ingredient
- How results were compared
- Results were compared between groups. · Study comparison: oral vitamin D3 plus standard care versus standard care alone; infection incidence 25% versus 45%
- Additional measurement information
- Primary outcome
- Measurement time
- 12 weeks
proinflammatory cytokine response
- A better result than the comparison group was reported.
What the comparison group used was not confirmed.
Single ingredientMeasurement and study conditions
- Study type
- Randomized controlled trial: subjects were randomly assigned to groups for comparison.
- Study population
- Human participants · Participant characteristics were not confirmed.
- Ingredients tested
- Single ingredient
- How results were compared
- Results were compared between groups.
- Measurement time
- Not confirmed.
recent URI
- No clear difference from the comparison group was found.General population · Separable contribution · 1-year follow-up
Measurement and study conditions
- Study type
- Randomized controlled trial: subjects were randomly assigned to groups for comparison.
- Study population
- Human participants · General population
- Ingredients tested
- Separable contribution
- How results were compared
- Results were compared between groups. · Study comparison: daily vitamin D3 versus placebo
- Additional measurement information
- Primary outcome
- Measurement time
- 1-year follow-up
response to cutaneous VZV antigen challenge
Other human research, including observational studies and reviews
- A change was reported before and after use. Its cause cannot be isolated.Deficiency group · Single ingredient · 14 weeks
Measurement and study conditions
- Study type
- Clinical trial
- Study population
- Human participants · Deficiency group
- Ingredients tested
- Single ingredient
- How results were compared
- Changes within the same group were compared. · Study comparison: within-person pre/post vitamin D3 replacement; no concurrent control
- Additional measurement information
- Secondary outcome
- Measurement time
- 14 weeks
Other measured outcomes (7)
SARS-CoV2 infection
Other human research, including observational studies and reviews
- An association was observed. This does not establish that the ingredient caused the change.General population · first COVID-19 wave
Measurement and study conditions
- Study type
- Observational study
- Study population
- Human participants · General population
- Ingredients tested
- Unknown intervention
- How results were compared
- Results were compared between groups. · Study comparison: supplemented individuals versus propensity-score-matched untreated controls; observational associati
- Additional measurement information
- Primary outcome
- Measurement time
- first COVID-19 wave
severe COVID-19
Other human research, including observational studies and reviews
- A change was reported, but the comparison could not be confirmed.Patient group
Measurement and study conditions
- Study type
- Meta-analysis
- Study population
- Human participants · Patient group
- Ingredients tested
- Unknown intervention
- How results were compared
- Study comparison: Observational association of vitamin-D deficiency/status with COVID-19 infection and severity outcom
- Additional measurement information
- Primary outcome
- Measurement time
- Not confirmed.
asthma exacerbation requiring treatment with systemic corticosteroids
Research with unclear study subject or type
- The study reported improvement in this measurement.Single ingredient
Measurement and study conditions
- Study type
- Meta-analysis
- Study population
- Recorded population category: Patient group. Whether the research involved humans needs confirmation.
- Ingredients tested
- Single ingredient
- How results were compared
- Results were compared between groups. · Study comparison: Vitamin D versus placebo across included randomized trials.
- Additional measurement information
- Primary outcome
- Measurement time
- Incidence across the included trial follow-up periods; no definitive subgroup interaction.
asthma/recurrent wheeze
Research with unclear study subject or type
- The study reported improvement in this measurement.
What the comparison group used was not confirmed.
Single ingredientMeasurement and study conditions
- Study type
- Meta-analysis
- Study population
- Study subject not identified
- Ingredients tested
- Single ingredient
- How results were compared
- Results were compared between groups.
- Measurement time
- Not confirmed.
respiratory tract infections
Research with unclear study subject or type
- A change was reported, but the comparison could not be confirmed.Single ingredient · varied across included trials
Measurement and study conditions
- Study type
- Systematic review
- Study population
- Recorded population category: General population. Whether the research involved humans needs confirmation.
- Ingredients tested
- Single ingredient
- How results were compared
- Study comparison: Summary count of meta-analyses reporting beneficial outcomes; comparator not specified
- Additional measurement information
- Secondary outcome
- Measurement time
- varied across included trials
risk of acute respiratory tract infection
Research with unclear study subject or type
- A change was reported, but the comparison could not be confirmed.Single ingredient
Measurement and study conditions
- Study type
- Meta-analysis
- Study population
- Study subject not identified
- Ingredients tested
- Single ingredient
- Measurement time
- Not confirmed.
risk of ARI
Research with unclear study subject or type
- A change was reported, but the comparison could not be confirmed.varied across trials
Measurement and study conditions
- Study type
- Meta-analysis
- Study population
- Recorded population category: General population. Whether the research involved humans needs confirmation.
- Ingredients tested
- Unknown intervention
- How results were compared
- Study comparison: IPD meta-analysis of vitamin D RCTs; abstract reports pooled outcome and subgroups but not trial-lev
- Additional measurement information
- Primary outcome
- Measurement time
- varied across trials
This result is held for interpretation. That does not mean research found no effect.
Outcome groups needing additional review (4)
- asthma exacerbations treated with systemic corticosteroids · Distinct papers needing additional review: 1Evidence criteria check: 1
- immune homeostasis · Distinct papers needing additional review: 1Evidence criteria check: 1
- incidence of first or only pneumonia · Distinct papers needing additional review: 1Evidence criteria check: 1
- inflammation · Distinct papers needing additional review: 1Evidence criteria check: 1
One paper can appear under multiple measured outcomes or review reasons, so these counts should not be added together.
Representative outcome and study details
Studies with an unspecified organism reported between-group improvement in asthma exacerbation requiring treatment with systemic corticosteroids.
Single-ingredient studies · Includes patient groups · between-group comparison
1 publications linked to this result
- Route, form, dose, or population details are incomplete, so the findings cannot be confirmed as directly comparable.
Data coverage and detailed study classifications
Paper counts are separated by research topic below. One paper may contribute to multiple findings.
Analysis status: Public-ready
Ingredient analysis date:
How the grade was determined: C
The 49.3 evidence score includes 2 independent human studies and 2 clinical studies in the representative benefit area. The C tier remains conservative because of the evidence centers on contextual or measured outcomes rather than general-use effects, limited repetition across independent human clinical studies.
The grade is based mainly on the research area with the most evidence. It does not mean the same result was found in other areas.
Papers linked to this ingredient overall: 126
Papers linked to this topic 18 · distinct papers 18 · papers with a confirmed human comparison 4 · papers needing additional review 7
A publication may appear in more than one count. These numbers should not be added. Ingredient-wide papers, topic-linked papers, and sources in outcome groups use different scopes. Adding source counts may count the same paper more than once.
- asthma exacerbation requiring treatment with systemic corticosteroids: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- asthma exacerbations treated with systemic corticosteroids: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- asthma/recurrent wheeze: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- immune homeostasis: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- incidence of first or only pneumonia: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- incidence of infection: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 1
- inflammation: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- proinflammatory cytokine response: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 1
- recent URI: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 1
- respiratory tract infections: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- response to cutaneous VZV antigen challenge: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- risk of acute respiratory tract infection: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- risk of ARI: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- SARS-CoV2 infection: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 1
- severe COVID-19: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
What the research found
recent URI
No clear difference in this measurement was found between the compared groups.
Controlled study in people · Separable contribution · General population
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
incidence of infection
The study reported improvement in this measurement.
Controlled study in people · Single ingredient · Patient group
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
proinflammatory cytokine response
The study reported improvement in this measurement.
Controlled study in people · Single ingredient · Unspecified population
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
asthma exacerbation requiring treatment with systemic corticosteroids
The study reported improvement in this measurement.
Meta-analysis · Single ingredient · Patient group
Between-group comparison
Analysis coverage and paper counts
1 paper · 2 measured outcomes
Review overlap with primary papers is unknown; counts stay separate.
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
asthma/recurrent wheeze
The study reported improvement in this measurement.
Meta-analysis · Single ingredient · Unspecified population
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
Review overlap with primary papers is unknown; counts stay separate.
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
response to cutaneous VZV antigen challenge
A change was reported before and after use. Its cause cannot be isolated.
Other evidence · Single ingredient · Deficiency group
Within-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
SARS-CoV2 infection
An association was observed. This does not establish that the ingredient caused the change.
Observational study · Unknown intervention · General population
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
respiratory tract infections
A change was reported, but the comparison could not be confirmed.
Review · Single ingredient · General population
Analysis coverage and paper counts
1 paper · 1 measured outcome
Review overlap with primary papers is unknown; counts stay separate.
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
risk of acute respiratory tract infection
A change was reported, but the comparison could not be confirmed.
Meta-analysis · Single ingredient · Unspecified population
Analysis coverage and paper counts
1 paper · 1 measured outcome
Review overlap with primary papers is unknown; counts stay separate.
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
risk of ARI
A change was reported, but the comparison could not be confirmed.
Meta-analysis · Unknown intervention · General population
Analysis coverage and paper counts
1 paper · 3 measured outcomes
Review overlap with primary papers is unknown; counts stay separate.
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
severe COVID-19
A change was reported, but the comparison could not be confirmed.
Meta-analysis · Unknown intervention · Patient group
Analysis coverage and paper counts
1 paper · 1 measured outcome
Review overlap with primary papers is unknown; counts stay separate.
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
asthma exacerbations treated with systemic corticosteroids
The study needs further checking before its result can be interpreted.
Meta-analysis · Unknown intervention · Patient group
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Review overlap with primary papers is unknown; counts stay separate.
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
immune homeostasis
The study needs further checking before its result can be interpreted.
Review · Single ingredient · Unspecified population
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Review overlap with primary papers is unknown; counts stay separate.
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
incidence of first or only pneumonia
The study needs further checking before its result can be interpreted.
Controlled study in people · Single ingredient · Patient group
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
inflammation
The study needs further checking before its result can be interpreted.
Review · Single ingredient · Patient group
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Review overlap with primary papers is unknown; counts stay separate.
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
Unspecified measured outcome
The study needs further checking before its result can be interpreted.
Animal study · indirect · Single ingredient · Patient group
This finding comes from animal or cell research. It does not establish the same effect in people.
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
Unspecified measured outcome
The study needs further checking before its result can be interpreted.
Controlled study in people · Single ingredient · Patient group
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
Unspecified measured outcome
The study needs further checking before its result can be interpreted.
Controlled study in people · Single ingredient · Unspecified population
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
How to read research findings
How should I read research findings?
Research guidesNo clear difference and an uninterpretable result are different
A reported null comparison contains a result. An abstract without an interpretable comparison leaves a question unresolved.
Paper counts and study counts are different
Count original research separately from research that reanalyzes it. Publication volume is neither replication nor a quality rating.
Side effects and combination findings
Findings from this ingredient alone are shown separately from those involving another supplement or medication.
No reviewed caution rules are available yet. Reported caution findings are shown below.
Review 3 combination findings and 0 findings that outperformed an ingredient alone.
Findings to review with care
Side effects reported for the ingredient alone are separated from findings involving another supplement or medication.
Side effects reported with this ingredient alone
Symptoms or adverse events reported in studies without another active ingredient.
adverse reactions (e.g., hypercalciuria, hypervitaminosis D, kidney stones, gastrointestinal symptoms, mild itch)1 papers
Six studies reported adverse reactions potentially attributable to vitamin D, occurring across treatment and control arms.Human studies · Meta-analysisReported improvements with combinations
Combination findings are grouped by how the study compared them. This is not a recommendation to combine ingredients.
Combinations with reported improvement
The combination showed improvement, but each ingredient's contribution is unclear.
오메가-3Combined vitamin D and omega-3 fatty acids showed a 31% reduction in autoimmune disease incidence compared to placebo, suggesting a potential additive effect.
BCAACombination with Vitamin D significantly improved appendicular skeletal muscle mass/height2 compared to control.
마그네슘Co-supplementation with Vitamin D and Magnesium resulted in significant improvements in behavioral function and mental health scores compared to placebo.