Unexpected Side Effect of Sunscreen
The growing use of sunscreens to prevent skin cancer and sun-induced wrinkling and as an adjunct to a new wrinkle treatment may have an unexpected side effect, particularly for older people, researchers say.
In a new study of Vitamin D synthesis and sun exposure, researchers at two medical centers found that constant blockage of the sun’s natural ultraviolet rays appeared to curtail an older person’s natural levels of Vitamin D.
The study, which focused on older people, was a follow-up to an initial test that found Vitamin D synthesis in young people was impaired when sunscreens were used all over the body and the research subjects were exposed to ultraviolet rays in a laboratory.
Expanded Study Needed
The dimension of the risk in the elderly in everyday life has yet to be quantified. Researchers hope to do an expanded study in which older people in a variety of climates, including California, are tested.
But based on the testing conducted so far, the study team leader and an independent expert said people 65 and older who spend time in the sun may want to consider taking Vitamin D supplements or switching to diets that include foods rich in Vitamin D.
If the sunblock-related vitamin deficiency is extensive enough, the researchers say, the depressed Vitamin D levels may result in an increased risk of bone loss, which in turn could increase chances for the type of hip fractures associated with osteoporosis.
Supplementing Vitamin D or changing diets to include more foods rich in it would be preferable to discontinuing sunscreen use, the researchers said, since damaging effects of the sun and the potential for melanoma and other skin cancers represents a far more significant risk.
And researchers involved in the new investigation speculate that, though their study pertained only to a group of 40 people whose average age was close to 65, it is possible that middle-aged and even young people may face the same hazard.
At issue is a study conducted by researchers at Jefferson Medical College in Philadelphia and the Southern Illinois University School of Medicine in Springfield. The team, led by Dr. Lois Matsuoka, compared the Vitamin D status of 20 people who had faithfully applied sunscreens for at least a year with 20 others who did not.
Inhibited Synthesis
In an earlier study, Matsuoka and other researchers reported Vitamin D synthesis seemed to be inhibited in a group of medical students who lathered their entire bodies in a sunscreen rated at sun protective factor (SPF) 8. That study found that artificial sunlight increased Vitamin D stores when no sunblock was used but that vitamin levels were unchanged when sunscreen was applied.
The new research on older people involved sunblocks rated at SPF 15, the level of protection dermatologists now recommend to prevent skin cancer.
Matsuoka said there is evidence the vitamin D impairment increases as the SPF rating goes up.
The latest group of sunscreen users, Matsuoka and three colleagues reported in the current issue of the journal Archives of Dermatology, had consistently abnormal low levels of Vitamin D. She concluded that the impairment by the sunscreens of the sun’s normal interaction with the skin was at fault.
The sunscreens involved all had as their major active ingredient para-aminobenzoic acid--commonly called PABA. It is the most common of a handful of active ingredients in commercial sunscreens.
In an editorial, Dr. Janet Hill Prystowsky, of the Columbia University College of Physicians and Surgeons in New York, said the finding may have greater relevance in view of the heavily promoted use of tretinoin, a prescription acne medication sold under the brand name Retin-ACQ, as a possible way to treat sun-induced, age-related wrinkling of the skin.
Special Attention Needed
Because Retin-A increases the skin’s normal sun sensitivity, doctors recommend that people also apply sunblock. Prystowsky speculated that the combination of the popularity of Retin-A and media campaigns by dermatologists to encourage sunblock use as a means of cancer-prevention necessitate special attention to the newly recognized potential vitamin-deficiency danger.
“I am concerned, especially about the elderly,” Prystowsky said. “The question of why the elderly develop hip fractures is of real concern. If we’re somehow influencing their Vitamin D status and that is contributory, we need to re-evaluate.
Matsuoka emphasized it is important for the elderly not to overreact. “I think our work is pretty strong,” she said. “The elderly who are using sunscreens every day to prevent skin cancer may also be people with poorer diets and who, because of poor diet, would not have as much Vitamin D.”
She said people 60 or older who have any reason to be concerned about their vitamin levels should check with their physicians. Diet modification in which consumption of foods rich in Vitamin D--including fortified milk, eggs and fish--may often be enough to counteract the effects of low vitamin levels, she said.
