Evidence Trace, complete trial record
In plain terms
In plain terms: Astaxanthin shows early signals in human research but the evidence is limited -- small trials, surrogate endpoints, or not yet independently replicated. It is an emerging area, not yet a proven one.
Astaxanthin
C
Limited: small, mixed or unreplicated trials
The endpoint this grade is based on: Surrogate biomarker endpoint, Skin moisture and elasticity, with oral astaxanthin from Haematococcus pluvialis algae at about 6 mg a day
The evidence as the record states it
Zhou et al. (Nutrients, 2021; PMID 34578794): 9 randomized trials of oral astaxanthin; skin moisture and elasticity improved against placebo, wrinkle depth did not. Tominaga et al. (Acta Biochimica Polonica, 2012; PMID 22428137): in the randomized double-blind arm, 36 men taking 6 mg a day for 6 weeks, wrinkles, elasticity and water loss through the skin improved and moisture showed only a trend; the paper's other arm was open-label. The skin trials read are manufacturer-affiliated. Ito et al. (Nutrients, 2018; PMID 29941810): 23 adults, less ultraviolet skin damage, one small trial. Ma et al. (Nutrition Research, 2022; PMID 35091276): 12 trials; malondialdehyde fell, C-reactive protein and tumor necrosis factor did not. Park et al. (Nutrition and Metabolism, 2010; PMID 20205737): 42 young women, 14 per group; a DNA damage marker fell, lipid peroxidation did not change, and some inflammatory markers rose at 8 mg. Coombes et al. (American Journal of Clinical Nutrition, 2016; PMID 26675778): 12 mg a day for a year changed neither oxidative stress markers nor arterial stiffness. Xia et al. (Pharmacological Research, 2020; PMID 32755613): no effect on LDL cholesterol, blood pressure or glucose; Leung et al. (Nutrients, 2022; PMID 35631193): LDL cholesterol lower. Liu et al. (Nutrients, 2026; PMID 42197030): creatine kinase lower after exercise, performance unchanged. Hecht et al. (Advances in Therapy, 2025; PMID 40014233): one manufacturer-run trial in 64 children with screen-related eye strain. The B covers skin moisture and elasticity only.
PMID 34578794 PMID 22428137 PMID 29941810 PMID 35091276 PMID 20205737 PMID 26675778 PMID 32755613 PMID 35631193 PMID 42197030 PMID 40014233
Evidence by specific use
Skin moisture and elasticity
Grade C
Zhou et al. (Nutrients, 2021; PMID 34578794): moisture SMD 0.53 and elasticity SMD 0.77 against placebo across 9 randomized trials, with high heterogeneity. Tominaga et al. (Acta Biochim Pol, 2012; PMID 22428137) is one of them. The trials read are manufacturer-affiliated, which is disclosed here. C, not B: skin moisture and elasticity are measured skin markers, not an established stand-in for a clinical outcome, and under the B definition such a marker qualifies for nothing above C (the rule applied to MitoQ's flow-mediated dilation in October 2026). The outside audit of October 2026 also found the positive results rest on within-group change and subsets in manufacturer-run trials.
PMID 34578794 PMID 22428137
Zhou et al. (Nutrients, 2021; PMID 34578794) found no pooled effect on wrinkle depth (SMD -0.26, 95% CI -0.58 to 0.06); the only positive wrinkle result is the 36-man arm of Tominaga et al. (Acta Biochim Pol, 2012; PMID 22428137). C.
PMID 34578794 PMID 22428137
Skin protection from ultraviolet light
Grade C
Ito et al. (Nutrients, 2018; PMID 29941810): the dose of ultraviolet light needed to redden the skin rose and moisture loss after exposure was smaller. One sponsor-run trial of 23 people: C.
PMID 29941810
Blood markers of oxidative stress
Grade C
Ma et al. (Nutr Res, 2022; PMID 35091276) found malondialdehyde lower; Coombes et al. (Am J Clin Nutr, 2016; PMID 26675778) and Liu et al. (Nutrients, 2026; PMID 42197030) found no change in oxidative markers, and Park et al. (Nutr Metab, 2010; PMID 20205737) was mixed with 14 people per group. Malondialdehyde is not an established stand-in for a clinical outcome. Mixed: C.
PMID 35091276 PMID 20205737 PMID 26675778 PMID 42197030
Cholesterol, blood pressure and arterial stiffness
Grade C
Xia et al. (Pharmacol Res, 2020; PMID 32755613) found no effect on LDL cholesterol, blood pressure or glucose; Leung et al. (Nutrients, 2022; PMID 35631193) found LDL cholesterol lower; Coombes et al. (Am J Clin Nutr, 2016; PMID 26675778) found arterial stiffness unchanged after a year. Pooled analyses disagree: C.
PMID 32755613 PMID 35631193 PMID 26675778
Muscle damage markers after exercise
Grade C
Liu et al. (Nutrients, 2026; PMID 42197030): creatine kinase and lactate dehydrogenase fell, but VO2max, time trials and power did not improve. Damage markers are not an established stand-in for a clinical outcome: C.
PMID 42197030
Screen-related eye strain in children
Grade C
Hecht et al. (Adv Ther, 2025; PMID 40014233): the questionnaire score improved 20% more than placebo; visual acuity and focusing did not differ. One manufacturer-run trial on a mostly self-reported endpoint: C.
PMID 40014233
Why Grade C and not Grade B
Grade C reflects early or limited human evidence -- small trials, surrogate endpoints, or preliminary findings not yet independently replicated. The evidence points in a promising direction but does not yet meet the standard for Grade B. A single well-powered, independently replicated trial with a meaningful endpoint would move this to Grade B or higher.
What would move this grade
A well-powered randomized trial with an objective, clinically meaningful primary endpoint and at least one independent replication would support Grade B or higher.
How to track whether this is working
Skin aging markers, eye health, exercise recovery time, oxidative stress markers (8-OHdG if available)