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.
Caffeine
Selected research topic
Fatigue and energy
Changes were observed before and after use, but they cannot be attributed to this ingredient.
Some publications still need interpretation checks and are kept separate from the findings below.
- Publications for this topic
- 2
- Human comparison publications
- 0
- Publications needing review
- 1
Findings in the studies
markers of fatigue
Other human research, including observational studies and reviews
- A change was reported before and after use. Its cause cannot be isolated.General population · Single ingredient · acute and 24 hours post-training
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
- Single ingredient
- How results were compared
- Changes within the same group were compared. · Study comparison: caffeine versus placebo; no significant between-group difference
- Additional measurement information
- Primary outcome
- Measurement time
- acute and 24 hours post-training
Representative outcome and study details
Human studies reported a within-group change in markers of fatigue.
Single-ingredient studies · Human studies · within-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: B
The 64.2 evidence score includes 23 independent human studies and 23 clinical studies in the representative benefit area. The B tier reflects evidence directness, repetition, and consistency together.
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: 67
Papers linked to this topic 2 · distinct papers 2 · comparison findings need further review · 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.
- markers of fatigue: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
What the research found
markers of fatigue
A change was reported before and after use. Its cause cannot be isolated.
Controlled study in people · Single ingredient · General population
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.
Unspecified measured outcome
The study needs further checking before its result can be interpreted.
Controlled study in people · Ingredient combination · Unspecified 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.
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.
QRS tachycardia1 papers
A 32‑year‑old woman experienced severe caffeine toxicity after ingesting 5000 mg, leading to presyncope, QRS tachycardia, metabolic acidosis, and hypokalemia, requiring ED treatment.Human studies · Observational studyReported 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.
비트루트 추출물In a randomized crossover trial of 20 healthy males, the combination of caffeine and beetroot juice significantly improved 1,000-m running performance compared to placebo (p < 0.01).
L-테아닌L-theanine combined with caffeine significantly reduced caffeine-induced tachycardia (17% vs 92%) and state anxiety compared to caffeine alone.
로디올라A randomized, double-blind, placebo-controlled trial in 48 male volleyball players found that combined Rhodiola rosea and caffeine supplementation significantly improved jump height, reduced power decline during high-frequency jumps, and lowered perceived exertion compared to placebo and single-agent groups.