Retinol is found in foods such as liver, eggs and milk, and appears to have an effect on cell differentiation and growth, the researchers noted.
Previous research in mice has found that retinol and related compounds can decrease the size of tumors and prolong survival in melanoma.
The current recommendation for vitamin A for adults is 700 micrograms to 900 micrograms a day. However, taking more than 2,800 micrograms a day can lead to significant side effects such as birth defects, liver abnormalities, reduced bone mineral density and mental problems, according to the U.S. National Institutes of Health.
Dr. Doris Day, a dermatologist at Lenox Hill Hospital in New York City, said she is unsure about the effectiveness of vitamin A supplements.
"I will say that based on data and research, using vitamin A on the skin has been helpful to protect against skin cancers," she said.
However, Day does think that vitamin A in the diet also protects against skin cancer. "Diet is your number-one source," she noted.
Supplements may have an additional benefit but they don't replace a healthy diet, she explained. "Everything you put into your body has an effect on your skin. Your skin is another organ system that affects and reflects your other organ systems. When you eat antioxidants, like vitamin A, you are supporting your skin in a direct way and you are increasing protection against [ultraviolet] radiation and repair cells after UV radiation," Day said.
But the best way to prevent skin cancer is to use sun protection and limit time spent in direct sun, Day stressed. "You need to be sun-smart," she said.
Dr. Robert Graham, an internist at Lenox Hill Hospital in New York City, added that based on these findings, "there is some promise of v
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