The supplement appears to work best when taken on a regular basis at least one week before sun exposure, he says. "It needs to be present in the body so that when the skin is exposed, the astaxanthin can stop the damage."
Although sold over-the-counter, sun-protection pills aren't cheap. BioAstin sells for $29 for 60 capsules and Heliocare sells for about $50 for 60 capsules.
Vitamin C may be a cheaper alternative. In a study published in April in the Proceedings of the National Academy of Sciences, researchers found that when cells in a culture were first treated with vitamin C, free-radical molecules were deactivated, protecting the cells from damage by UVA light.
Sunscreens with UVA protection are important but not very effective, says Dr. Gerd Pfeifer, a professor of biology at City of Hope who conducted the vitamin C research. "Most chemicals that protect against UVA are destroyed by sunlight. We need to find a better way to protect against UVA."
Antioxidants, on the other hand, only work on free radicals created by UVA radiation, the longer-wavelength rays that penetrate the skin more effectively than UVB light.
Though many researchers think antioxidants for sun protection will work best in pill form, a few sunscreen manufacturers are adding antioxidants such as vitamins C and E and astaxanthin to products. Questions remain about how the effectiveness of topical products.
"There have been some sunscreens with vitamin C, but it's problematic to get it at a high enough concentration and have it stable," Pfeifer says. "But eventually I think something will be developed."
Pfeifer says he doubts taking vitamin C in a pill form will supply enough protection to mitigate sun damage because it's easily excreted by the body.
No pill should replace sunscreen, says Lim, who doesn't recommend sun-protection supplements to his patients because he fears they might cut back on sunscreen.
Adds Cysewski: "I would never recommend anyone just take astaxanthin and not use sunscreen. This just provides an additional line of defense."
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More information on sun safety, skin care and sunscreens:
* How to minimize sun damage, from the American Academy of Dermatology: www.aad.org/public/sunsafety
* A fact sheet on sunscreens, from the American Academy of Dermatology: www.aad.org/public/news/derminfo/dinfosunscreenfaq.htm
* An explanation on the types of skin cancer and risk factors, from the Skin Cancer Foundation: www.skincancer.org/prevention/index.php
* A primer on sun damage and sun protection, including the Food and Drug Administration's monograph on sunscreen ingredients, from the Environmental Protection Agency: www.epa.gov/sunwise/doc/sunscreen.pdf