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
Nutrient status
Some measured outcomes improved in human comparison studies. Read these findings with their populations and conditions.
Findings from a combination study cannot be attributed to this ingredient alone.
Animal and cell findings do not establish the same effect in people.
Some findings concern patients or people with a deficiency.
- Publications for this topic
- 24
- Human comparison publications
- 1
- Publications needing review
- 19
Findings in the studies
25(OH)D concentrations
- A better result than the comparison group was reported.Patient group · Single ingredient
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: 400, 2000, or 4000 IU/day vitamin D3 through delivery; dose groups compared
- Additional measurement information
- Primary outcome
- Measurement time
- at delivery and one month before delivery
serum 25(OH) D
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
Measurement and study conditions
- Study type
- Randomized controlled trial: subjects were randomly assigned to groups for comparison.
- Study population
- Human participants · Deficiency group
- Ingredients tested
- Single ingredient
- How results were compared
- Changes within the same group were compared. · Study comparison: within-group serum 25(OH)D change in D3 arm; placebo arm remained unchanged, direct between-group es
- Additional measurement information
- Biomarker
- Measurement time
- phase 1 and phase 2, each 3 months
serum vitamin D
Other human research, including observational studies and reviews
- A change was reported before and after use. Its cause cannot be isolated.Patient group · Single ingredient · 12 weeks
Measurement and study conditions
- Study type
- Clinical trial
- Study population
- Human participants · Patient group
- Ingredients tested
- Single ingredient
- How results were compared
- Changes within the same group were compared. · Study comparison: pre/post within-patient change; no control group described
- Additional measurement information
- Biomarker
- Measurement time
- 12 weeks
serum 25-hydroxyvitamin D3 levels
Animal and cell research · indirect evidence
- A change was reported in animal or cell research.
Several ingredients were tested together, so this ingredient’s individual effect is unknown.
Combination study · 16 weeksMeasurement and study conditions
- Study type
- Controlled trial
- Study population
- This is animal research. The specific characteristics of the subjects need further review.
- Ingredients tested
- Ingredient combination
- How results were compared
- Comparison unclear · Study comparison: Vitamin-D-withdrawal diet in d-galactose-induced aging mice versus vitamin-D-sufficient condition
- Additional measurement information
- Biomarker
- Measurement time
- 16 weeks
Other measured outcomes (1)
serum 25(OH)D levels
Research with unclear study subject or type
- A change was reported, but the comparison could not be confirmed.Single ingredient · varied across included studies
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
- Study comparison: Pooled population-intervention estimate; comparator not specified in abstract
- Additional measurement information
- Biomarker
- Measurement time
- varied across included studies
This result is held for interpretation. That does not mean research found no effect.
Outcome groups needing additional review (10)
- 25(OH)D3 · Distinct papers needing additional review: 2Direction unclear: 2
- 25-hydroxyvitaminD3 (25OHD3) blood levels · Distinct papers needing additional review: 1Direction unclear: 1
- 25-OH-D3 concentration · Distinct papers needing additional review: 1Evidence criteria check: 1
- 25OHD · Distinct papers needing additional review: 1Evidence criteria check: 1
- fractional calcium absorption · Distinct papers needing additional review: 1Direction unclear: 1
- intestinal P and Ca absorption · Distinct papers needing additional review: 1Evidence criteria check: 1
- serum 25(OH)D · Distinct papers needing additional review: 1Evidence criteria check: 1
- serum levels of 25(OH)D · Distinct papers needing additional review: 1Evidence criteria check: 1
- total 25(OH)D · Distinct papers needing additional review: 1Evidence criteria check: 1
- vitamin D levels · 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
Partial research summary
Studies with an unspecified organism reported a change with no confirmed comparison group in serum 25(OH)D levels.
These conditions come from related studies and may not describe a single paper.
Single-ingredient studies · Scope not specified · Human studies · Includes patient groups · comparator not confirmed
3 publications linked to this result (2 awaiting review included)
- Study conditions differ; results are shown descriptively and are not pooled.
- Some publications have not cleared source or interpretation review.
- Some papers could not be reviewed, so this summary covers only findings that could be confirmed.
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 24 · distinct papers 24 · papers with a confirmed human comparison 1 · papers needing additional review 19
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.
- 25(OH)D concentrations: Sources represented in this measurement group: 2 · Distinct papers with human comparisons for this outcome: 1
- 25(OH)D3: Sources represented in this measurement group: 2 · Distinct papers with human comparisons for this outcome: 0
- 25-hydroxyvitaminD3 (25OHD3) blood levels: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- 25-OH-D3 concentration: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- 25OHD: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- fractional calcium absorption: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- intestinal P and Ca absorption: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- serum 25(OH) D: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- serum 25(OH)D: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- serum 25(OH)D levels: Sources represented in this measurement group: 3 · Distinct papers with human comparisons for this outcome: 0
- serum 25-hydroxyvitamin D3 levels: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- serum levels of 25(OH)D: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- serum vitamin D: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- total 25(OH)D: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- vitamin D levels: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
What the research found
25(OH)D concentrations
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.
serum 25(OH) D
A change was reported before and after use. Its cause cannot be isolated.
Controlled study in people · 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.
serum vitamin D
A change was reported before and after use. Its cause cannot be isolated.
Other evidence · Single ingredient · Patient 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.
serum 25(OH)D levels
A change was reported, but the comparison could not be confirmed.
Meta-analysis · Single ingredient · 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.
serum 25-hydroxyvitamin D3 levels
A change was reported in animal or cell research.
Animal study · indirect · Ingredient combination · Deficiency group
This finding comes from animal or cell research. It does not establish the same effect in people.
Several ingredients were used together. This does not establish the effect of this ingredient alone or synergy.
The comparison could not be confirmed.
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.
25(OH)D concentrations
The study needs further checking before its result can be interpreted.
Meta-analysis · Single ingredient · General 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.
25(OH)D3
The study needs further checking before its result can be interpreted.
Observational study · 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
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
25(OH)D3
The study needs further checking before its result can be interpreted.
Observational study · Unknown intervention · General population
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.
25-hydroxyvitaminD3 (25OHD3) blood levels
The study needs further checking before its result can be interpreted.
Observational study · 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
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
25-OH-D3 concentration
The study needs further checking before its result can be interpreted.
Animal study · indirect · Unknown intervention · Unspecified population
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.
25OHD
The study needs further checking before its result can be interpreted.
Meta-analysis · Single ingredient · General 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.
fractional calcium absorption
The study needs further checking before its result can be interpreted.
Controlled study in people · 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
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
intestinal P and Ca absorption
The study needs further checking before its result can be interpreted.
Animal study · indirect · Single ingredient · Unspecified population
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.
serum 25(OH)D
The study needs further checking before its result can be interpreted.
Review · Unknown intervention · General 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.
serum 25(OH)D levels
The study needs further checking before its result can be interpreted.
Controlled study in people · 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
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
serum 25(OH)D levels
The study needs further checking before its result can be interpreted.
Observational study · Unknown intervention · General population
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.
serum levels of 25(OH)D
The study needs further checking before its result can be interpreted.
Controlled study in people · Single ingredient · Patient group
Within-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.
total 25(OH)D
The study needs further checking before its result can be interpreted.
Meta-analysis · Unknown intervention · General 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.
Unspecified measured outcome
The study needs further checking before its result can be interpreted.
Controlled study in people · 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
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
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.
Meta-analysis · Unknown intervention · Unspecified population
The comparison could not be confirmed.
Analysis coverage and paper counts
2 papers · 2 measured outcomes
2 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.
Review · Unknown intervention · 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.
vitamin D levels
The study needs further checking before its result can be interpreted.
Controlled study in people · Single ingredient · Deficiency 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.
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.