Comparison
Biological comparison
This compares mechanisms and evidence profiles. It is not a ranking, a recommendation, or a safety assessment.
Niacinamide only
- Nicotinate metabolism (NAD salvage)
- NAD+ dependent deacetylation (sirtuins)
- Keratinocyte differentiation
Shared pathways
- No shared curated pathways
L-Ascorbic acid only
- Collagen biosynthesis and modifying enzymes
- Detoxification of reactive oxygen species
- Melanin biosynthesis
Niacinamide
C6H6N2O · Skin barrier
Niacinamide is a form of vitamin B3 involved in cellular metabolism as a precursor of NAD+. It has been studied for barrier-related, pigmentation-related and sebum-related endpoints in skin.
Targets
- Nicotinamide phosphoribosyltransferase (NAMPT) — targets (high confidence)
- Poly(ADP-ribose) polymerase 1 (PARP1) — inhibits (medium confidence)
- Sirtuin 1 (SIRT1) — modulates (medium confidence)
- ADP-ribosyl cyclase CD38 — inhibits (low confidence)
L-Ascorbic acid
C6H8O6 · Antioxidant
L-ascorbic acid is vitamin C: a water-soluble reducing agent and an essential cofactor for the prolyl and lysyl hydroxylases that mature collagen.
Targets
- Prolyl 4-hydroxylase subunit alpha-1 (P4HA1) — activates (high confidence)
- Procollagen-lysine 5-dioxygenase (PLOD1) — activates (high confidence)
- Tyrosinase (TYR) — inhibits (low confidence)
- Sodium-dependent vitamin C transporter 2 (SLC23A2) — targets (medium confidence)
Evidence engine
Moderate
Some human evidence exists, but replication or sample sizes are limited.
Skinceptor Evidence Index
60
experimental · of 100
This index is a research-navigation aid describing how much evidence exists and how it was produced. It is not a medical safety score, an efficacy guarantee, or a clinical recommendation.
Study composition
- Human2
- In-vitro2
- Review1
- Total studies
- 5
- Human studies
- 2
- Largest sample
- 50
- Range
- 2000–2018
Index breakdown
- Study design quality47% × 28%
Mean design weight across curated studies (meta-analysis 1.0, RCT 0.9, other human 0.7, review 0.45, animal 0.35, in-vitro 0.25).
- Human evidence share67% × 22%
Proportion of curated evidence measured in people rather than cells or animals.
- Evidence volume82% × 14%
Log-scaled count of curated studies, so volume alone cannot dominate the score.
- Largest sample size57% × 12%
Log-scaled largest reported sample size across curated human studies.
- Replication67% × 12%
Independent human studies, capped at three; one study is never treated as replicated.
- Recency60% × 7%
Linear decay over a twenty-year window from the most recent curated publication.
- Source traceability40% × 5%
Share of curated studies with a verified PMID or DOI in this dataset.
Insufficient comparable evidence for quantitative synthesis.
Evidence engine
Moderate
Some human evidence exists, but replication or sample sizes are limited.
Skinceptor Evidence Index
57
experimental · of 100
This index is a research-navigation aid describing how much evidence exists and how it was produced. It is not a medical safety score, an efficacy guarantee, or a clinical recommendation.
Study composition
- Human1
- Randomised controlled trial1
- In-vitro2
- Review1
- Total studies
- 5
- Human studies
- 2
- Largest sample
- 19
- Range
- 1991–2013
Index breakdown
- Study design quality51% × 28%
Mean design weight across curated studies (meta-analysis 1.0, RCT 0.9, other human 0.7, review 0.45, animal 0.35, in-vitro 0.25).
- Human evidence share67% × 22%
Proportion of curated evidence measured in people rather than cells or animals.
- Evidence volume82% × 14%
Log-scaled count of curated studies, so volume alone cannot dominate the score.
- Largest sample size43% × 12%
Log-scaled largest reported sample size across curated human studies.
- Replication67% × 12%
Independent human studies, capped at three; one study is never treated as replicated.
- Recency35% × 7%
Linear decay over a twenty-year window from the most recent curated publication.
- Source traceability20% × 5%
Share of curated studies with a verified PMID or DOI in this dataset.
Insufficient comparable evidence for quantitative synthesis.