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 B12
Selected research topic
Nutrient status
Findings differ across measurements or study conditions. The results below keep them separate.
Findings from a combination study cannot be attributed to this ingredient alone.
Some findings concern patients or people with a deficiency.
- Publications for this topic
- 22
- Human comparison publications
- 4
- Publications needing review
- 12
Findings in the studies
homocysteine
- A better result than the comparison group was reported.
Several ingredients were tested together, so this ingredient’s individual effect is unknown.
Patient group · Combination study · 12 weeksMeasurement and study conditions
- Study type
- Randomized controlled trial: subjects were randomly assigned to groups for comparison.
- Study population
- Human participants · Patient group
- Ingredients tested
- Ingredient combination
- How results were compared
- Results were compared between groups. · Study comparison: Vitamin B complex versus placebo; combination effect cannot be attributed to vitamin B12 alone.
- Additional measurement information
- Biomarker
- Measurement time
- 12 weeks
tHcy
- A better result than the comparison group was reported.Deficiency group · Single ingredient · 12 months
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
- Results were compared between groups. · Study comparison: B12 versus placebo on a shared multinutrient background
- Additional measurement information
- Secondary outcome
- Measurement time
- 12 months
tHcy concentration
- A better result than the comparison group was reported.
What the comparison group used was not confirmed.
Separable contributionMeasurement 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
- Separable contribution
- How results were compared
- Results were compared between groups.
- Measurement time
- Not confirmed.
Vitamin B12 deficiency
- Results were mixed for this outcome.Patient group
Measurement and study conditions
- Study type
- Systematic review
- Study population
- Human participants · Patient group
- Ingredients tested
- Unknown intervention
- How results were compared
- Results were compared between groups. · Study comparison: PPI users versus non-users; pooled vitamin B12 deficiency odds ratio slightly elevated, but heteroge
- Additional measurement information
- Biomarker
- Measurement time
- Not confirmed.
Other measured outcomes (5)
indirect DNA damage
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
- Review
- Study population
- Recorded population category: Deficiency group. Whether the research involved humans needs confirmation.
- Ingredients tested
- Single ingredient
- How results were compared
- Study comparison: Review-level mechanistic claims; no clinical comparative outcome
- Additional measurement information
- Mechanistic outcome
- Measurement time
- Not confirmed.
levels of B12
Research with unclear study subject or type
- A change was reported, but the comparison could not be confirmed.
Measurement and study conditions
- Study type
- Systematic review
- Study population
- Recorded population category: Patient group. Whether the research involved humans needs confirmation.
- Ingredients tested
- Unknown intervention
- How results were compared
- Study comparison: observational serum/plasma B12 association across BMI categories; not supplementation
- Additional measurement information
- Biomarker
- Measurement time
- Not confirmed.
serum vitamin B12 level
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
- Systematic review
- Study population
- Recorded population category: Patient group. Whether the research involved humans needs confirmation.
- Ingredients tested
- Single ingredient
- How results were compared
- Study comparison: Within-study serum vitamin B12 changes after supplementation; review does not report a common compar
- Additional measurement information
- Biomarker
- Measurement time
- Varied across included studies
vitamin B12
Research with unclear study subject or type
- A change was reported, but the comparison could not be confirmed.
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: Higher vs lower vitamin B12 concentrations in observational studies
- Additional measurement information
- Biomarker
- Measurement time
- cross-sectional; not robust in prospective analyses
Vitamin B12 levels
Research with unclear study subject or type
- No clear difference in this measurement was found between the compared groups.Single ingredient
Measurement and study conditions
- Study type
- Meta-analysis
- Study population
- Recorded population category: General population. Whether the research involved humans needs confirmation.
- Ingredients tested
- Single ingredient
- How results were compared
- Results were compared between groups. · Study comparison: No statistically significant differences among B12 administration routes for vitamin B12 levels
- Additional measurement information
- Primary outcome
- Measurement time
- Not confirmed.
- A change was reported, but the comparison could not be confirmed.
Measurement and study conditions
- Study type
- Meta-analysis
- Study population
- Recorded population category: Patient group. Whether the research involved humans needs confirmation.
- Ingredients tested
- Unknown intervention
- How results were compared
- Study comparison: vitiligo patients vs controls
- Additional measurement information
- Biomarker
- Measurement time
- Not confirmed.
This result is held for interpretation. That does not mean research found no effect.
Outcome groups needing additional review (4)
- complete resolution · Distinct papers needing additional review: 1Evidence criteria check: 1
- hemoglobin levels · Distinct papers needing additional review: 1Applicability check needed: 1
- homocysteine concentrations · Distinct papers needing additional review: 1Evidence criteria check: 1
- serum B12 · 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 both no clear between-group difference and a change with no confirmed comparison group for Vitamin B12 levels.
These conditions come from related studies and may not describe a single paper.
Single-ingredient studies · Scope not specified · Includes patient groups · between-group comparison · comparator not confirmed
3 publications linked to this result (1 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: B
The 57.4 evidence score includes 1 independent human studies and 1 clinical studies in the representative benefit area. The B 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: 96
Papers linked to this topic 22 · distinct papers 22 · papers with a confirmed human comparison 4 · papers needing additional review 12
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.
- complete resolution: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- hemoglobin levels: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- homocysteine: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 1
- homocysteine concentrations: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- indirect DNA damage: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- levels of B12: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- serum B12: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- serum vitamin B12 level: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- tHcy: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 1
- tHcy concentration: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 1
- vitamin B12: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- Vitamin B12 deficiency: Sources represented in this measurement group: 2 · Distinct papers with human comparisons for this outcome: 1
- Vitamin B12 levels: Sources represented in this measurement group: 3 · Distinct papers with human comparisons for this outcome: 0
What the research found
homocysteine
The study reported improvement in this measurement.
Controlled study in people · Ingredient combination · Patient group
Several ingredients were used together. This does not establish the effect of this ingredient alone or synergy.
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.
tHcy
The study reported improvement in this measurement.
Controlled study in people · Single ingredient · Deficiency 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.
tHcy concentration
The study reported improvement in this measurement.
Controlled study in people · Separable contribution · 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.
vitamin B12 deficiency
Results for this measurement were mixed; no consistent conclusion can be drawn.
Review · Unknown intervention · Patient group
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.
vitamin B12 levels
No clear difference in this measurement was found between the compared groups.
Meta-analysis · Single ingredient · General 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.
indirect DNA damage
A change was reported, but the comparison could not be confirmed.
Review · Single ingredient · Deficiency 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.
levels of B12
A change was reported, but the comparison could not be confirmed.
Review · 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.
serum vitamin B12 level
A change was reported, but the comparison could not be confirmed.
Review · 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.
vitamin B12
A change was reported, but the comparison could not be confirmed.
Meta-analysis · 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.
vitamin B12 levels
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.
complete resolution
The study needs further checking before its result can be interpreted.
Review · Unknown intervention · Deficiency 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.
hemoglobin levels
The study needs further checking before its result can be interpreted.
Other evidence · Ingredient combination · Patient group
Several ingredients were used together. This does not establish the effect of this ingredient alone or synergy.
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.
homocysteine concentrations
The study needs further checking before its result can be interpreted.
Review · Unknown intervention · 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.
serum B12
The study needs further checking before its result can be interpreted.
Controlled study in people · Ingredient combination · General population
Several ingredients were used together. This does not establish the effect of this ingredient alone or synergy.
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
The comparison could not be confirmed.
Analysis coverage and paper counts
2 papers · 2 measured outcomes
2 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 · 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.
Observational study · 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
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.
Other evidence · 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
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.
Other evidence · 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
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
Vitamin B12 deficiency
The study needs further checking before its result can be interpreted.
Other evidence · Unknown intervention · 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.
Vitamin B12 levels
The study needs further checking before its result can be interpreted.
Meta-analysis · Unknown intervention · 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.
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.
Findings to review with care
Side effects reported for the ingredient alone are separated from findings involving another supplement or medication.
Cautions reported with another supplement or medication
These studies reported worsening outcomes, reduced absorption, or other cautions with combined use. They do not predict an individual's outcome.
AntacidsAntacids may alter vitamin B12 absorption and utilization, increasing deficiency risk.
MetforminMetformin-treated T2DM patients are at higher risk of vitamin B12 deficiency and more severe neuropathy symptoms; supplementation may prevent or treat these conditions.
Proton pump inhibitorsPPI use may impact the absorption of vitamin B12, resulting in a slightly increased risk of deficiency.