Benefits
Skin moisture and elasticity
In a pooled analysis of eight small randomized trials of oral astaxanthin (mostly 4 to 12 mg a day for 4 to 16 weeks, largely in healthy middle-aged Japanese women), skin moisture and elasticity improved versus control groups, but wrinkle depth did not change significantly, and results varied between trials. None of the trials tested Zanthin itself.
Screen-related eye strain
In a 12-week trial in 64 children with heavy screen use, 4 mg a day of astaxanthin lowered eye-strain and visual-fatigue scores more than placebo, while acuity, focusing and tear tests did not differ. In 60 adults, 9 mg a day for 6 weeks better kept visual acuity after screen work only in those aged 40 and over. Both trials were run by astaxanthin suppliers.
Antioxidant markers in the blood
In an 8-week trial in 42 young women, 2 or 8 mg a day of astaxanthin lowered a DNA-damage marker but not lipid peroxidation. A meta-analysis of 9 randomized trials found only a borderline effect on oxidative-stress markers versus control and called the antioxidant effect in humans uncertain.
Mechanism of action
Membrane-spanning antioxidant
Astaxanthin is a fat-soluble carotenoid that sits across cell membranes and can neutralize reactive oxygen species. In people, its measurable effect on oxidative-stress markers has been inconsistent.
Clinical trials
Systematic review and meta-analysis of randomized controlled trials of oral astaxanthin on skin aging, plus two open-label topical studies (Zhou et al. 2021, Nutrients).
Nine randomized trials of oral astaxanthin (eight pooled), each with 16 to 65 mostly healthy, middle-aged participants, largely Japanese women.
Oral astaxanthin improved skin moisture (standardized mean difference 0.53) and elasticity (0.77) versus control, but wrinkle depth did not change significantly (-0.26, p = 0.11). Heterogeneity was moderate to high. Generic astaxanthin, not Zanthin.
Randomized, double-blind, placebo-controlled trial of 4 mg/day astaxanthin for 84 days; half of the authors were employees of the AstaReal supplier group (Hecht et al. 2025, Adv Ther).
64 children aged 10 to 14 with at least 4 hours of daily screen time and mild to moderate eye-strain symptoms.
Eye-strain questionnaire scores improved more than with placebo (a 20% between-group difference) and visual-fatigue scores were 27% lower. Stereopsis after visual load improved, but visual acuity, near focusing, tear production and safety measures did not differ from placebo.
Randomized, double-blind, placebo-controlled parallel trial of a diet containing 9 mg/day astaxanthin for 6 weeks, sponsored by an astaxanthin supplier (Sekikawa et al. 2023, J Clin Biochem Nutr).
60 healthy adults.
In participants aged 40 and over, corrected visual acuity after screen work was better preserved than with placebo; there was no difference in those under 40, and functional visual acuity and pupil response did not differ.