Astaxanthin
Astaxanthin is a red-orange xanthophyll carotenoid and the pigment that gives salmon, trout, shrimp and krill their pink colour. Haematococcus pluvialis is one of the most important natural sources and is particularly valuable because it can accumulate exceptionally high levels of astaxanthin, but astaxanthin is also synthesised naturally by other microalgae, yeasts and bacteria. Animals cannot make it themselves; they obtain it through the food chain, and supplements obtain it from cultivated algae.
Astaxanthin is a carotenoid — one of the natural pigments that give salmon, shrimp and krill their reddish colour — and it is commonly described as an antioxidant. Two further points are regularly noted in the literature. Unlike beta-carotene, astaxanthin is not converted into vitamin A in the human body, so it carries no vitamin A activity. And it is fat-soluble, which is why it is normally taken with a meal containing some fat. These are descriptions of the ingredient itself, not statements about what a product does.
About this ingredient
Astaxanthin belongs to the xanthophylls, the oxygen-containing branch of the carotenoid family, and has the molecular formula C40H52O4. Only algae, some bacteria and some yeasts synthesise it. Salmon, trout, shrimp, crab, lobster, krill and salmon roe acquire it through the food chain from microalgae and plankton and store it in muscle, shell and eggs, which is why those tissues are pink or red. The commercial source for food supplements is cultivated Haematococcus pluvialis: the alga accumulates astaxanthin in its resting cyst stage under growth stress such as intense light or nutrient shortage, and EFSA describes the dried algal meal used in food as containing roughly 5 % astaxanthin by weight.
Dietary sources
Astaxanthin is not an essential nutrient. There is no Thai RDI for it, no EU nutrient reference value, and food composition tables generally do not list it. In an ordinary diet it comes almost entirely from seafood: the flesh of salmon and trout, the shell and meat of shrimp, crab and lobster, krill, and salmon roe. Amounts vary widely with species, season and — for farmed fish — the astaxanthin supplied in feed.
Forms & absorption
Two things set one astaxanthin raw material apart from another: where it comes from and the form it is in. Astaxanthin from Haematococcus pluvialis algae is the same natural form found in wild salmon and krill, and in that form it is naturally bound to fatty acids rather than standing alone. Astaxanthin made synthetically is a mixture of forms, only part of which matches the natural one. Thai FDA guidance on key ingredients in dietary supplements lists astaxanthin under Haematococcus pluvialis, and specifies the permitted extraction methods as milling, supercritical carbon dioxide or acetone. Astaxanthin is fat-soluble, so supplements are normally softgels in an oil base and are taken with a meal that contains some fat.
Research status
Most human research on astaxanthin consists of small, short trials — typically a few dozen participants over four to twelve weeks — at intakes of about 4 to 12 mg a day. Systematic reviews of that body of work describe it as varied in design, dosage and raw material, and not yet conclusive.
Safety & considerations
Astaxanthin from food supplements is intended for adults, and background intake also comes from fish and shellfish; it is not a product for children or adolescents. Always follow the amount printed on the label of the product in front of you. If you are pregnant or breastfeeding, take prescription medicines, or have an allergy to algae or shellfish, speak to a doctor or pharmacist before starting any supplement. Dietary supplements are not intended to prevent, treat or cure any disease.
Quality markers
Four things are worth checking on an astaxanthin label. First, the source organism: Haematococcus pluvialis should be named. Second, whether the milligram figure refers to astaxanthin itself or to the algal extract that contains it — for example, an extract standardised at 2 % astaxanthin needs 300 mg to deliver 6 mg of astaxanthin, so the two numbers are not interchangeable. Third, whether a named raw-material brand is declared, which indicates a documented supply chain and a specified extraction method. Fourth, packaging and storage: astaxanthin is degraded by light, heat and oxygen, so softgels in opaque blister or bottle packaging kept away from sunlight retain their content better. Every dietary supplement sold in Thailand also carries an FDA (อย.) registration number on the label, which can be checked against the Thai FDA public register.
- EFSA – Safety of astaxanthin as a novel food in food supplements (2020) ↗
- EFSA – Safety of algal meal from Haematococcus pluvialis containing astaxanthin (2025) ↗
- PubChem (NCBI) – Astaxanthin compound summary ↗
- Brendler & Williamson – Astaxanthin: How much is too much? A safety review (Phytother Res 2019) ↗
- Thai FDA – Advice on the use of key ingredients in dietary supplements (8 July 2024), item 158 Haematococcus pluvialis ↗
This page is general educational information about a nutrient — it describes the nutrient itself and is not a statement about any particular product. Dietary supplements are food, not medicine, and have no effect in preventing or treating disease. The references listed above are public-institution sources, not product claims.
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