4–12 mg/day with a meal containing fat.
Review: astaxanthin, a carotenoid from the microalga Haematococcus, is a potent antioxidant with promising biological activities. Most of the evidence is preclinical or laboratory-based; solid clinical trials in people for specific indications are lacking.
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Astaxanthin is an intensely red carotenoid produced by some microalgae (mainly Haematococcus pluvialis) and by some yeasts, which is concentrated up the marine food chain until it accumulates in large amounts in wild salmon, trout, krill, shrimp, and flamingos, all animals whose pink-orange color reflects precisely the astaxanthin stored in their tissues; it is one of the carotenoids with the highest measured antioxidant capacity, superior to that of beta-carotene, vitamin E, or coenzyme Q10 in several standardized assays.
Unlike most antioxidants, astaxanthin can cross the blood-brain barrier and the blood-retinal barrier, and it is incorporated into cell membranes in a position that allows it to protect both the lipophilic and the hydrophilic fraction of the membrane simultaneously; this structural peculiarity is what makes it especially interesting for protecting tissues with high metabolic demand and exposure to oxidative stress, such as the eye, the brain, and muscle during intense exercise.
The indication with the best clinical evidence is skin protection: several randomized trials have shown that doses of 4 to 12 milligrams daily for 8 to 16 weeks reduce loss of hydration, wrinkle depth, and signs of photoaging, and increase elasticity and the thickness of the stratum corneum; the effect is modest but consistent and is especially noticeable in women over 40 with skin photoaged by accumulated sun exposure.
The mechanism combines antioxidant protection of keratinocytes against UV-induced free radicals, modulation of skin inflammation, and possibly an effect on collagen synthesis; it does not replace sunscreen (it does not absorb UV) but it does act as "protection from within" that complements classic topical protection, a combination with reasonable synergy.
In endurance sport, several studies have shown modest improvements in time to exhaustion, in the use of fat as fuel, and in post-exercise recovery with doses of 4 to 12 milligrams daily over several weeks; the effect is small in magnitude but measurable, and is attributed to mitochondrial protection against the intense oxidative stress that accompanies sustained high-intensity exercise.
In post-strength-training recovery, some trials have shown reductions in markers of muscle damage (CK, LDH) and in subjective muscle soreness in the days after demanding sessions; these data are interesting for athletes with high training loads who want to complement classic recovery strategies (sleep, nutrition, massage).
In digital eye strain (from screens), several trials have shown subjective improvements in the sensation of eye fatigue, dryness, and difficulty with accommodation with 6-12 milligrams daily for 4-12 weeks; these effects have been attributed to specific antioxidant protection of the retinal photoreceptors and to the improvement in choroidal circulation described in mechanistic studies.
In the cardiometabolic profile, several small studies have shown modest reductions in triglycerides, improvements in HDL, and a modest reduction in blood pressure with prolonged use at doses of 12-18 mg/day; in markers of chronic low-grade inflammation (C-reactive protein, oxidative markers), the antioxidant effect translates into measurable improvements that may have clinical relevance in the long term.
The doses studied range from 4 to 18 milligrams daily, taken once with a meal containing fat (absorption is highly dependent on the lipid matrix; without fat, less than 30 percent is absorbed); softgel capsules with vegetable oil are the most common form and have the best bioavailability; clinical effects on skin and performance usually appear between 4 and 12 weeks.
It is one of the carotenoids with the best safety profile: practically no adverse effects at the doses studied over months, and no relevant documented drug interactions; one harmless side effect is the slight pink-orange color that can appear in the skin with prolonged use at high doses, similar to that produced by beta-carotene (carotenemia), reversible when the supplement is stopped; no specific risks in pregnancy have been described at dietary doses, but moderation is advised because of limited data.
Information, not medical advice. Scientific evidence reflects the quality of the studies.