AHK-Cu vs GHK-Cu: Which Is Better for Skin?
GHK-Cu wins this on evidence. It has human wound and skin data behind it. AHK-Cu has one unreplicated dish study and no human trial at all. Use GHK-Cu…
- AHK-Cu
- GHK-Cu
Best Interventions for Hair and Nail Health, Ranked by Evidence
Every intervention Outliyr has scored for hair and nail health, ranked by its BioHarmony score for this use case rather than its overall rating. The number beside each name is how well that one thing works for hair and nail health; the tier beside it is what it is worth once safety, cost and effort are counted across everything else.
19 of 77 evaluated interventions score 3.0+ out of 10 for hair and nail health · 4 comparisons
Ranked for Hair and Nail Health
Category
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Red Light Therapy
Hair-nail earns 8.0/10 because Lanzafame 2013 reported a 35% hair-count increase versus 2% sham after 16 weeks in androgenetic alopecia. Red Light Therapy fits hair better than nails because follicles are living…
Read the Red Light Therapy report → -
Spermidine
A 6.8/10 for hair-nail fits Spermidine because Schwarz 2022 supports direction more than certainty. The existing rationale points to this narrower claim: this verified source randomized 100 participants and found a spermidine-based…
Read the Spermidine report → -
Glycine
Glycine hair nail earns 6.5/10 because Holecek 2025 anchors the most relevant signal. Glycine fits hair nail because glycine participates in sleep signaling, glutathione, collagen, methylation, and nervous-system balance, depending on the…
Read the Glycine report → -
Essential Amino Acids
For users targeting hair and nail support, Essential Amino Acids earns 6.0/10 because Wittholz 2024 reports Systematic review found heterogeneity high enough that planned meta-analysis was not possible. Hughes 2024 points in…
Read the Essential Amino Acids report → -
TB-500 (Thymosin Beta-4 Fragment)
Hair Nail is a 5.5/10 use case for TB-500 (Thymosin Beta-4 Fragment), not a blanket claim. Hair-follicle support rests mainly on animal and mechanistic evidence. Philp 2004 title-matches thymosin beta-4 effects on…
Read the TB-500 (Thymosin Beta-4 Fragment) report → -
Collagen Peptides
The 5.0/10 hair nail score reflects evidence plus practical constraints. Hexsel 2017 reported improved brittle nails in an open-label trial. Hair evidence is much thinner and should not be inferred from nail…
Read the Collagen Peptides report → -
Metformin
Metformin receives a 5.0 / 10 rating for the hair-nail use case, based on limited data from a PCOS meta-analysis that reported modest reductions in hirsutism when insulin resistance improved Lord 2003.…
Read the Metformin report → -
Ca-AKG (Calcium Alpha-Ketoglutarate)
The practical hair-nail read on Ca-AKG (Calcium Alpha-Ketoglutarate) is 5.0/10 because Shahmirzadi 2020 anchors the strongest signal. The existing rationale points to this narrower claim: No hair or nail evidence. Keep neutral…
Read the Ca-AKG (Calcium Alpha-Ketoglutarate) report → -
GHK-Cu
Hair-nail stays at 4.5 because GHK-Cu is common in hair products and has follicle-adjacent mechanisms, but direct human hair-regrowth trial support is much weaker than minoxidil or red light therapy. Pickart 2018…
Read the GHK-Cu report → -
Rapamycin
INSUFFICIENT_EVIDENCE for hair or nail benefit; use mainly as an adverse-change watch item rather than a target.
Read the Rapamycin report → -
NAC (N-Acetylcysteine)
The trichotillomania (hair-pulling) data per Grant 2009 is about compulsive behavior, not hair growth; there is no evidence NAC improves hair or nail quality directly.
Read the NAC (N-Acetylcysteine) report → -
Whole-Body Vibration
No evidence. Whole-body vibration should not be marketed for hair or nail growth.
Read the Whole-Body Vibration report → -
Thymosin Beta-4 (Tβ4)
Hair growth claims for Tβ4 are entirely preclinical, with rodent and in vitro evidence that Tβ4 activates hair-follicle stem cells, per Gao 2015. No peer-reviewed human clinical trial of native Tβ4 for…
Read the Thymosin Beta-4 (Tβ4) report → -
Semaglutide
Hair shedding can occur from rapid weight loss, caloric deficit, or micronutrient gaps, so hair and nail effects skew negative.
Read the Semaglutide report → -
Tongkat Ali
The androgenic mechanism cuts both ways. Tongkat Ali may support body-hair androgen tone but could worsen androgenetic alopecia in DHT-sensitive men.
Read the Tongkat Ali report → -
Astaxanthin
Skin and microcirculation overlap may help appearance indirectly. No strong hair or nail endpoint evidence.
Read the Astaxanthin report → -
Vitamin C (Ascorbic Acid)
Hair and nail health scores 3.0/10. Through its collagen-cofactor role, adequate vitamin C supports the connective tissue underlying hair follicles and nail beds, and deficiency produces corkscrew hairs and brittle, fragile tissue…
Read the Vitamin C (Ascorbic Acid) report → -
Hyaluronic Acid
Hair and nails rate 3.0/10. Scalp and skin hydration overlap may help appearance indirectly, but there is no strong hair-growth or nail-strength endpoint evidence for oral or topical HA.
Read the Hyaluronic Acid report → -
C15 (Pentadecanoic Acid)
No published C15:0 trial has measured hair count, hair shedding, nail growth, or nail strength. The follicle and nail-matrix extrapolation from cell membranes is speculative and not supported by Robinson 2024 (Robinson…
Read the C15 (Pentadecanoic Acid) report →
Nothing matches those filters.
Comparisons that judge hair and nail health
Head-to-head reports and category rankings that name a winner on this use case.
Colostrum vs Collagen Peptides: Which Should You Buy?
These two get sold as the same thing, a scoop for gut and skin, and they share almost no mechanism. Colostrum is a gut and immune product: gut…
- Colostrum
- Collagen Peptides
HBOT vs Red Light Therapy: Which Is Better for Recovery?
Buy the panel. Red light therapy scores 8.0 against HBOT's 6.2, costs $17 to $43 a month against $3,000 to $6,000, and does not lose a single use…
- Hyperbaric Oxygen Therapy
- Red Light Therapy
Spermidine vs Urolithin A: Which Is Better for Longevity?
Spermidine scores 7.6 and urolithin A 6.5, and they clean up different messes. Spermidine drives broad autophagy: autophagy 8.0, cardiovascular 7.8, longevity 7.5. Urolithin A drives selective mitophagy…
- Spermidine
- Urolithin A
Questions about hair and nail health
What scores highest for hair and nail health?
Red Light Therapy, at 8.0 out of 10 for hair and nail health. Hair-nail earns 8.0/10 because Lanzafame 2013 reported a 35% hair-count increase versus 2% sham after 16 weeks in androgenetic alopecia.
What is the cheapest thing that works for hair and nail health?
Of the top-scoring options, Glycine is the least expensive at about $2 a month, scoring 6.5 out of 10 for hair and nail health.
How many interventions has Outliyr scored for hair and nail health?
19 of the 77 interventions evaluated for hair and nail health score 3.0 out of 10 or better, which is the cut-off for appearing on this page.
