Why not just step outside for your dose of vitamin D?
Studies show that regular exposure to the sun, without sunscreen, allows your skin to produce vitamin D naturally. But how much sun do you really need? As it turns out, production of vitamin D in your skin is highly individual and varies greatly depending on several factors, including:
Skin color, current tan level and time spent in the sun. Your body produces a limited amount of vitamin D everyday. Once you reach your limit, you will only cause damage to your skin by going beyond that amount. If you have darker skin, this can take two to six times longer, depending on your pigmentation. But be careful, it doesn’t matter what your skin color or ethnicity. Anyone can develop skin cancer. In fact, melanoma is often more difficult to detect in people with skin of color. If not diagnosed early, the cancer can spread, making treatment less effective.4
Weather conditions. Cloud cover and air pollution with large amounts of ozone can reduce the amount of UV radiation that reaches the earth’s surface—and your skin. Conversely, surface reflection (sand, water, snow) can increase the amount.
Latitude and altitude (elevation). UV light is strongest at the equator where sunlight shines down at a direct angle and has the shortest distance to travel to get through the earth’s atmosphere. The longer the angle (the further away from the equator), the less intense the sunlight. At altitude, UV radiation is more intense since there is less atmosphere to absorb it.
Season. The sun’s rays are mild in the spring, more intense in summer, and in some areas, almost non-existent in winter.
Time of day. UVB rays are the most intense between the hours of 10am and 2pm. While it may be the ideal time for Vitamin D production, it’s also the time of day when exposure to the sun dramatically increases your risk of skin damage.
Sunscreen and clothing. It’s true, clothing and sunscreens prevent the sun from helping your body produce Vitamin D. But just as you wouldn’t dream of going stark naked in the midday sun, you shouldn’t go without sunscreen either. Ever.
Since there are so many factors that influence your body’s ability to use sunlight to produce vitamin D, there’s really no definitive way to know when enough is enough. And, because the consequences of overexposure are downright dangerous, you’re actually safer sticking to a healthy diet high in vitamin D and adding supplements if necessary to ensure you’re getting an adequate dose.
References
1Wolpowitz D, Gilchrest BA. The vitamin D questions: how much do you need and how should you get it? J Am Acad Dermatol 2006;54:301-17. [PubMed abstract]
2American Academy of Dermatology. Position statement on vitamin D. November 1, 2008.
3Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.
4http://www.aad.org/media-resources/stats-and-facts/prevention-and-care/skin-of-color Accessed June 16, 2011.
