Astaxanthin

Astaxanthin provides the rich pink color observed in various aquatic species including the salmonids (e.g., salmon) and crustaceans (e.g., crabs, lobster, shrimp), and even some nonaquatic species such as the flamingo (whose diet includes some astaxanthin-producing organisms). The carotenoids found in phytoplankton, algae and plants (including garlic, citrus, spinach, peppers, corn and many others) normally participate in those organisms' photosynthetic processes by acting as secondary light-absorbing molecules. Salmonids and flamingos don't actually produce astaxanthin but instead obtain it from other animals they consume. The richest source of astaxanthin by far is the algae Haemococcus pluvialis, which is used commercially as a feed additive to provide color to “farm-raised” salmon, rainbow trout among others. Wild fish receive their color from astaxanthin found in krill and other crustaceans they feed upon. The astaxanthin that is contained in living lobsters is complex with proteins called carotenoproteins that actually imparts a bluish-brown color to these animals. However, when the carotenoproteins are denatured, as occurs during the high temperatures associated with cooking, the astaxanthin is liberated and the bright red coloration we associate with a lobster dinner results.(2) Providing the coloration to such marine animals, thus enhances their economic value (e.g. few people would find a dull lobster or salmon steak attractive on their plate). Some recent studies have actually found that astaxanthin also provides an antioxidant and nutritive role for the health of the marine life.(3, 4)

In order for a particular antioxidant to function in the eye, that compound must cross the blood-retinal barrier. The blood-retinal barrier is similar in its function and structure to the blood-brain barrier, which is (1) in helping to prevent the unhindered passage of compounds into the central nervous system from the periphery and (2) regulating which compounds will pass. Due to the small molecular weight of astaxanthin and its fat solubility, it appears to easily penetrate the central nervous system which is a characteristic not typically seen with all carotenoids or antioxidants in general. Lutein and zeaxanthin are the carotenoid antioxidants that have been reported to improve visual performance in both normal subjects and those with ocular diseases, including macular degeneration and cataracts.(28) Antioxidants for the eye participate in the visual process by absorbing light to produce images and to protect the retina from damage due to decreasing oxidation (due to incoming light and resultant high energetic photons) of photoreceptor cells. It is important to note that one non-provitamin A carotenoid, cantaxanthine, which is commonly used in tanning regimens, has been reported in both laboratory animals and humans to cause an increase in deposits in the retina.(29)