Astaxanthin

What it is

Astaxanthin is a red carotenoid, a plant pigment related to beta-carotene. It is made by microalgae and builds up in seafood such as salmon, shrimp and krill [1]. Supplements are usually made from the microalga Haematococcus pluvialis [2].

How it might work

Astaxanthin is proposed to act as an antioxidant and anti-inflammatory agent, which may protect skin from UV damage [2]. These effects were first shown in animal studies, and human trials have given only partial support [3].

What the research says

Skin. The best-supported benefit is for skin ageing. A meta-analysis (a study that pools many trials) of nine randomized trials found oral astaxanthin improved skin moisture (standardized mean difference 0.53) and elasticity (0.77) compared with placebo, but did not significantly reduce wrinkle depth [2]. A systematic review of 11 clinical studies, mostly small trials in healthy Japanese women, concluded that doses of 3 to 6 mg a day improved skin texture and moisture and seemed to protect against UV damage [1]. In a 10-week trial of 23 healthy people taking 4 mg a day, the dose of UV light needed to cause skin redness was higher with astaxanthin than with placebo [4].

Cholesterol and blood fats. A meta-analysis of seven trials in 321 adults at risk of metabolic syndrome found a significant drop in LDL cholesterol, with marginal reductions in total cholesterol and systolic blood pressure [5]. A separate meta-analysis of antioxidant supplements found astaxanthin lowered LDL by 0.11 mmol/L, total cholesterol by 0.22 mmol/L and triglycerides by 0.46 mmol/L, and raised HDL by 0.13 mmol/L [6].

Oxidative stress and inflammation. A meta-analysis of 12 trials with 380 participants found astaxanthin lowered malondialdehyde, a marker of oxidative damage, and lowered interleukin-6 in people with type 2 diabetes, but did not change C-reactive protein (CRP) or tumor necrosis factor-alpha [3]. A wider meta-analysis of carotenoids did find astaxanthin lowered CRP by 0.30 mg/L [7].

Exercise. A 2026 meta-analysis of 24 trials found astaxanthin lowered creatine kinase, a marker of muscle damage, but did not improve VO2max, time-trial performance or power [8]. Another meta-analysis of 11 trials in 346 healthy people found improved physical performance, especially with doses of 20 mg or more and supplementation beyond 12 weeks [9]. In a crossover trial of 12 cyclists, 12 mg a day for 7 days shortened a 40 km time trial by 1.2% [10]. But in 32 well-trained cyclists, 20 mg a day for four weeks did not improve time-trial performance [11].

Fatigue and thinking. In 24 healthy volunteers, four weeks of astaxanthin plus sesamin helped recovery from mental fatigue compared with placebo [12]. The meta-analysis of 11 trials found only a marginal effect on cognitive accuracy and none on reaction time [9].

Eye strain. A trial of 64 children aged 10 to 14 with screen-related eye strain found that 4 mg a day for 84 days improved symptom scores (a 20% difference between groups), though the authors work for the manufacturer [13].

Doses used in studies

Skin studies used 3 to 6 mg a day [1], including 4 mg a day for 10 weeks [4]. The eye strain trial used 4 mg a day for 84 days [13]. Exercise trials used 12 mg a day for 7 days [10] and 20 mg a day for 4 weeks [11]. Liver-enzyme trials used 6 to 12 mg a day for 4 to 48 weeks [14].

Safety and interactions

Common side effects: no serious adverse events were reported in the skin studies reviewed [1], and a trial in children found no differences from placebo in safety measures [13]. Liver: a meta-analysis of five trials (196 people) found astaxanthin raised the liver enzyme ALT by an average of 1.92 U/L, with no change in AST, GGT or ALP; the authors called for longer trials [14]. Upper intake limits: the trials above used up to 20 mg a day, and no upper limit was reported. Medicine interactions: none were reported in the studies reviewed. Pregnancy and breastfeeding: the studies reviewed did not report on these. People with liver disease or on liver-affecting medicines should ask a doctor first, given the ALT finding.

Caveats and open questions

Most skin trials were small, in healthy Japanese women, and many were funded by commercial entities [1]. The cholesterol trials are few and measure blood markers, not heart attacks [5]. Exercise results disagree between meta-analyses and trials [8][9][11]. Several trials are underway, including one on brain aging (NCT07379437), one on fatigue and sports performance (NCT07630870) and one on asthma in polluted areas (NCT07507682).