Astaxanthin is a red-orange pigment that occurs in the natural diets of many aquatic species, including salmon, trout, and shrimp. It is closely related to more commonly known carotenoids such as beta-carotene or lutein. Astaxanthin isolated from crustacean wastes or produced synthetically. Astaxanthin can also be farmed from unicellular green alga called Haematococcus pluvialis or certain types of yeast and then prepared for commercial use. It is highly bioavailable because it binds to a lipid (fat) molecule and enters the bloodstream more readily than other antioxidants. Astaxanthin is a fat-soluble nutrient that is able to cross the blood-brain barrier, which enhances its effectiveness.

Astaxanthin is a member of the carotenoid family. These molecules are associated with many of the colors that you see in leaves, flowers and fruit. They are one of the most abundant molecules in the world and give nature its wide variety of colors. Carotenoids have a long structure called the polyene system and may also have ring groups at one or either end. The differences in the polyene and ring structures are what varies the carotenoids and their corresponding colors due to different light absorbencies. Astaxanthin is a red pigment and the predominant carotenoid of most crustacean species. Interestingly, when astaxanthin binds to different protein, it can appear green, yellow, blue or brown. When these "carotenoproteins" are denatured by cooking, astaxanthin is released and the red color becomes apparent again.

The carotenoid chemicals that make flamingos pink are the same as those that tint salmon and trout. Since they are not broken down and have extremely low water solubility, they are deposited in the feathers of flamingos and in the fat of the fish. In fish farms and bird parks, carotenoids are added to the feed to create the pleasing pink colour, but this has no effect on palatability or health. A number of suppliers now make a synthetic "nature-identical" version of the carotenoid astaxanthin and it is also possible (but expensive) to obtain commercial quantities of the natural colour from cultured yeast and algae.