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Sun exposure has both positive and negative aspects: Without enough sunlight, the body cannot produce adequate amounts of vitamin D, which is essential for proper absorption and use of calcium. And sunlight deficiency in the winter months is linked with seasonal depression. Too much sun, however, damages the skin, and increases the skin cancer risks. The cumulative effect of years of exposure to the sun’s ultraviolet rays can cause patches of severe skin damage that can progress to nonmelanoma forms of skin cancer (known as basal cell or squamous cell cancer). There are about one million new cases of nonmelanoma skin cancer in the United States each year.

Vitamin A, an antioxidant nutrient found in foods such as eggs and fish, has been shown in many studies to prevent and reverse cancerous changes in cells in some parts of the body, including the skin. One previous study found that people taking 25,000 IU of vitamin A per day for up to five years had a 32% reduction in risk of developing a common form of skin cancer.

In the current study, 129 people with severe sun damage on their forearms were randomly assigned to receive 25,000 IU; 50,000 IU; or 75,000 IU of vitamin A per day or placebo for one year. Biopsies of the forearm skin were done at the beginning and end of the study. Only 25% of people taking placebo had less skin damage at the end of the study than at the beginning; by contrast, 65% of those receiving 25,000 IU, 81% of those taking 50,000 IU, and 79% of those taking 75,000 IU of vitamin A per day had less damaged skin after one year. There was no sign of toxicity from any amount of vitamin A.

The results of this study add to the evidence that long-term use of vitamin A can repair skin damage from sun exposure, and specifically suggest that 50,000 IU per day is enough to provide maximum protection. Furthermore, up to 75,000 IU of vitamin A per day appeared to be safe for at least one year. These findings are especially important given the rising incidence of skin cancer in many parts of the world.

Although vitamin A did not cause any toxic effects in this study, long-term use of large doses of vitamin A can cause negative side effects such as hair loss, dry skin, nausea, and liver damage. Older people and those who consume large amounts of alcohol are at increased risk of developing adverse effects from vitamin A supplements. To be on the safe side, people interested in taking vitamin A in the amounts reported in the current study should be monitored by a doctor. Also, pregnant women should not take more than 10,000 IU of vitamin A per day without the supervision of a doctor.

While the body can convert beta-carotene into vitamin A, the extent of that conversion is limited. Consequently, taking large amounts of beta-carotene would not have the same benefits as taking vitamin A itself.

Maureen Williams, ND, received her bachelor’s degree from the University of Pennsylvania and her Doctorate of Naturopathic Medicine from Bastyr University in Seattle, WA. She has a private practice in Quechee, VT, and does extensive work with traditional herbal medicine in Guatemala and Honduras. Dr. Williams is a regular contributor to Healthnotes Newswire.