While the most notable carotenoid is the vitamin A precursor b-carotene, another carotenoid has received much attention lately - astaxanthin. Chemically, astaxanthin is classified as a xanthophyll, which is a family of non-provitamin A carotenoids. It is a fat-soluble nutrient with a unique molecular structure, giving it excellent antioxidant capacity. Lower organisms synthesize astaxanthin by proceeding through a number of important intermediate chemical compounds including phytoene, lycopene, b-carotene and canthaxanthin. Both astaxanthin and canthaxanthin are examples of chemicals called conjugated keto-carotenoids, and both are further classified as xanthophylls. While b-carotene is a vitamin A precursor, astaxanthin cannot be converted to vitamin A.
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.(1) 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.(2),(3)
Tablets, hard shell capsules and softgel capsules.
Astaxanthin appears to be absorbed in the blood in the same way as other carotenoids. Carotenoids are absorbed by passive diffusion through the intestinal mucosa after being emulsified and solubilized in lipid micelles which are incorporated into chylomicrons when exiting the intestinal mucosal cells. They are transported in the blood after being transferred from the chylomicrons to lipoproteins.(4)
To date there has been no toxicity reported with the supplementation of astaxanthin in animal or human studies.(5),(6)
There is a substantial body of literature including in vitro studies, pre-clinical studies and several human clinical trials that support the use of astaxanthin as a dietary supplement. The data consistently suggests that astaxanthin may be an effective therapeutic tool for a variety of conditions and diseases, including cardiovascular, immune, inflammation, and neuro-degenerative concerns.(7),(8),(9),(10) In laboratory studies, astaxanthin has been reported to be typically at least 10 times more potent as an antioxidant than the other standard carotenoids such as canthaxanthin, b-carotene, lutein, lycopene, tunaxanthin and zeaxanthin.(11),(12) When compared with vitamin E in laboratory studies, astaxanthin's antioxidant potential was from approximately 80 times to as much as 550 times greater!(13),(14)
The anti-cancer activity of carotenoids and related compounds has been the focus of much attention since epidemiological reports of an association between low levels of certain carotenoids and various types of cancers.(15) Some of the cancers studied with respect to the carotenoid association include lung, esophageal, stomach, colon, rectal, prostate, breast, cervical, ovarian, endometrial, bladder and skin. Carotenoids may be of benefit in the prevention or the amelioration of cancers via their ability to scavenge free radicals, inhibit the growth of certain tumors, inhibit malignant transformation, enhance immune function, and upregulate anti-cancer genes.(16) Astaxanthin has been reported in laboratory studies to be highly effective in preventing the growth of various tumors.(17),(18)
Carotenoids are also reported beneficial in helping decrease cardiovascular diseases, particularly high cholesterol levels or hypercholesterolemia. Many studies have been performed on the various carotenoids in decreasing oxidation of LDL cholesterol (so called "bad" cholesterol) and thereby decreasing the incidence of arteriosclerosis.(19),(20),(21) As the carotenoids are exclusively transported by lipoproteins, this suggests that they might protect these particles against oxidation. The xanthophylls have been reported to be superior to other carotenoids in the process.(22) One laboratory study of interest reported that astaxanthin actually increased HDL cholesterol levels, a positive effect for cardiovascular health.(23) Researchers found that astaxanthin decreased triglycerides, increased HDL-cholesterol and increased serum adiponectin proving to be beneficial to patients with mild hyperlipidemia.(24)
There have been quite a few laboratory animal studies that have demonstrated the ability of astaxanthin to enhance antibody responses and enhance certain aspects of immunity.(25),(26) Chronic bacterial (H. pylori) infection causes the production of DNA-damaging free radicals. Recent experimental studies, both in vivo and in vitro, have shown that vitamin C and astaxanthin are not only free radical scavengers but also show antimicrobial activity against H. pylori.(27) In a recent study using mice infected with H. pylori, astaxanthin was found to significantly reduce bacterial load and gastric inflammation, while also being able to modulate cytokine release (a function of immunity) in splenocytes harvested from these treated animals.(28) A human study was conducted with astaxanthin being tested in H. pylori -positive patients.(29) When administered five times per day for three weeks (8 mg doses), astaxanthin significantly decreased gastritis in all subjects, even though they remained positive for H. pylori. More research should be performed to determine if there is potential utility of astaxanthin in the overall therapy of H. pylori infection along with general immune enhancement in humans. Researchers found that astaxanthin supplementation decreased DNA damage, decreased inflammation and enhanced immune response in young women.(30)
The carotenoids in general play an essential role in the physiological function and overall health of the eye. Most of the information regarding the role of pro vitamin A carotenoids in the visual system has focused on b-carotene and its metabolic by-product vitamin A. However, more information has recently appeared that documents the importance of the antioxidant role of a number of carotenoid and non-carotenoid compounds in the eye. Astaxanthin has been studied for its strong antioxidant properties and was found to improve vision in patients with age-related maculopathy.(31)
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.(32) 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.(33)
The results of a study revealed that supplementation with astaxanthin may help prevent dementia.(34)
Foods containing astaxanthin are salmon, shrimp, krill, crab, trout, lobster, red seabream, fish eggs and yeast (Xanthophyllomyces dendrorhous). The micro-algae, haematococcus pluvialis, is the richest source of natural astaxanthin.