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
Digestion and gut health
Human comparison studies did not find a clear difference in some measured outcomes.
Some findings concern patients or people with a deficiency.
- Publications for this topic
- 3
- Human comparison publications
- 1
- Publications needing review
- 1
Findings in the studies
microbiome α-diversity
- No clear difference from the comparison group was found.Patient group · Single ingredient · 16 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: vitamin D versus placebo
- Additional measurement information
- Secondary outcome
- Measurement time
- 16 weeks
microbiome composition
Research with unclear study subject or type
- A change was reported, but the comparison could not be confirmed.varies across studies
Measurement and study conditions
- Study type
- Systematic review
- Study population
- Recorded population category: General population. Whether the research involved humans needs confirmation.
- Ingredients tested
- Unknown intervention
- Additional measurement information
- Secondary outcome
- Measurement time
- varies across studies
This result is held for interpretation. That does not mean research found no effect.
Outcome groups needing additional review (1)
- gut microbial diversity · Distinct papers needing additional review: 1Direction unclear: 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 a change with no confirmed comparison group in microbiome composition.
Scope not specified · comparator not confirmed
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 3 · distinct papers 3 · papers with a confirmed human comparison 1 · papers needing additional review 1
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.
- gut microbial diversity: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- microbiome composition: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- microbiome α-diversity: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 1
What the research found
microbiome α-diversity
No clear difference in this measurement was found between the compared groups.
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.
microbiome composition
A change was reported, but the comparison could not be confirmed.
Review · Unknown intervention · 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.
gut microbial diversity
The study needs further checking before its result can be interpreted.
Other evidence · Single ingredient · Deficiency 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.
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.