Astaxanthin (pronounced asta-zan-thin), widely used as a food coloring agent and nutritional supplement, has been studied for decades. It is one of the most potent antioxidants found in nature. The U.S. Food and Drug Administration have labeled it Generally Recognized as Safe (GRAS). It is chemically classified as a carotenoid, but unlike many other carotenoids it does not convert to Vitamin A. This is an important astaxanthin dosage issue, because Vitamin A toxicity is a serious health threat.
Commercial astaxanthin is usually produced synthetically because it generally costs about a third as much as it would coming from natural sources. Chemically, there is a difference; synthetic astaxanthin has three stereoisomers in approximately 1:2:1 proportions, whereas natural source astaxanthin stereoisomer ratios vary considerably from species to species. Stereoisomer ratios do not appear to be an astaxanthin dosage issue, however. Combining nutritional supplements with medication can be dangerous and consultation with competent health care professionals is appropriate. For example, in some cases astaxanthin lowers blood pressure, generally a plus, but potentially hazardous for someone already taking medication to lower blood pressure. Georgetown University Medical Center expert, Harry G. Preuss, did an extensive review of studies regarding astaxanthin safety in 2001. He reported no hazard for people taking dosages as high as half an ounce per day, provided they were not taking medication and concluded that there were no more safety concerns than the use of other carotenoids.
Free radicals are highly reactive particles missing an electron from their outer shell. They have potential to damage DNA until another particle stabilizes them by donating an electron. Free radicals are a major cause of aging damage, second only to the Hayflick limit. Astaxanthin is a free radical scavenger, several hundred times more potent than Vitamin E. Astaxanthin dosage for optimal nutritional support seems to be about four milligrams per day. Take care to allow for differences in concentration. For example, 200 milligrams of a two percent extract translates to four milligrams of astaxanthin.