The most commonly reported astaxanthin side effects are harmless pigment changes, such as a slightly orange tint to the skin or to stool. Even at high doses, no toxic effects have been observed, either in animals or humans. Other, less common astaxanthin side effects have a greater impact, and side effects such as low blood pressure and shifts in hormone levels can have serious health implications.
Astaxanthin is most commonly used as an additive to animal feed, and it adds pigment to crabs, shrimp, lobsters and salmon, giving them their familiar reddish orange color. As an animal feed supplement, astaxanthin is generally recognized as safe, according to the United States Code of Federal Regulations, and most people are able to consume astaxanthin-fed seafood without any reaction at all. In 1999, the U.S. Food and Drug Administration cleared astaxanthin as a food ingredient for human consumption.
As a dietary supplement, astaxanthin is most often used as an antioxidant to reduce cholesterol. Advocates also recommend astaxanthin to improve eye health and treat carpal tunnel syndrome, arthritis, muscle injury, gastrointestinal complaints and male infertility. It should be noted, however, that there is insufficient evidence to support any of these claims, and there is no proven health benefit to this supplement.
Common astaxanthin side effects include increased pigmentation, hair growth, shifts in hormone levels and low blood pressure. Reduced calcium levels, decreased libido and breast enlargement in men have also been observed, but these astaxanthin side effects are rarer. Allergic reactions also are possible and can be quite dangerous. Astaxanthin and astaxanthin-fed foods should be avoided by anyone with a known allergy to the substance.
Drug interactions are another serious concern. For instance, blood pressure medication might be amplified by astaxanthin and can cause blood pressure to dip dangerously low. Hormone treatments and birth control can be affected by the supplement’s effects on hormone levels. Similar cross-reactions have been observed with some antihistamines, and asthma medications might not react well to astaxanthin. Liver enzymes, which are responsible for removing a variety of drugs from the blood, also can be affected, resulting in increased levels of these drugs remaining in circulation.
Reactions also are possible with other supplements and herbal remedies. Saw palmetto, black cohosh or other medications that affect hormones might react unpredictably. Astaxanthin side effects such as low blood pressure and reduced calcium levels can be amplified by substances with similar effects. Use of other carotenoid antioxidants, such as beta carotene and lycopene, with astaxanthin will reduce absorption and is not recommended.