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Possible Hazards of Sunscreens, Sun Avoidance, or Both. When used generously and appropriately, sunscreen products and sun avoidance help reduce the severity of many aging skin disorders, including squamous cell cancers. There are certain concerns, however. Although sunscreens help prevent squamous cell carcinomas and other skin disorders, sunscreen use may not protect against basal cell and melanoma cancers, and may even increase the risk of getting them. It is important to note, however, that sunscreens themselves are not harmful. Unfortunately, some people use the wrong products, use them unwisely, or mistakenly fail to avoid direct exposure to sunlight.
The reasons for this possible increased risk are unclear, though some theories include the following:
- Until recently, many sunscreens blocked UVB rays and not UVA, the more deeply penetrating rays now known to be especially dangerous. Past studies may not have reflected the effects of the broad-spectrum sunscreens now available, which block both UVA and UVB rays.
- People who apply sunscreens may feel safe and stay in the sun longer than is safe during intense UV hours. Even if a person doesn't sunburn, UVA rays can still penetrate the skin and do harm.
- People may not put on enough sunscreen. Most people apply only 20 - 60% of the recommended amount of sunscreen, which can provide significantly less SPF protection than what is on the label.
Sunscreen Use May Increase the Risk for Health Problems Related to Sunlight Deficiencies. There is significant concern that underexposure to sunlight, due to the use of sunscreens or sun-avoidance measures, may produce other health problems, such as the following:
- Vitamin D Deficiency. Vitamin D is found in only a few foods, such as fortified dairy products and fish, but it is produced in the skin in response to UVB sunlight. UVB rays may outshine dietary supplements for building the body's vitamin D reserves. Without an appropriate mix of diet and supplements, vigorous sun protection measures may increase a person's risk for developing vitamin D deficiency. Vitamin D is important for preventing rickets and osteoporosis, and it may reduce the risk of some cancers. People who need to avoid sunlight and whose diet is low in foods that contain vitamin D should check with their doctor about taking supplements. People with darker skin are at higher risk for deficiencies from sun protection than those with whiter skin. Note: vitamin D is toxic in high doses. Most doctors recommend 400 IU a day (for young adults) to 800 - 1000 IU a day (for middle-aged and older adults). Doses up to 2,000 IU a day are considered safe.
The bottom line is that modest "doses" of sunlight may be healthful, but taking vitamin D may provide similar benefits without damaging the skin.
Review Date: 10/15/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, In-Depth Reports; Associate
Professor of Medicine, Harvard Medical School; Physician,
Massachusetts General Hospital. Also reviewed by David Zieve, MD,
MHA, Medical Director, A.D.A.M., Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)
