The dark side of sunlight avoidance -- and how to escape it

Sunlight (or its ultraviolet component to be exact) is needed for the body to produce vitamin D, whose deficiency leads to bone loss, poor immunity and, possibly, increased cancer risk. Experts believe that adequate vitamin D status requires ten to fifteen minutes of sun exposure at least two times per week to the face, arms, hands, or back without sunscreen. Some people, especially those with darker skin or unusually low rate of skin synthesis of vitamin D, may require more. Furthermore, recent research indicates that vitamin D levels above what's minimally adequate may have various health and longevity benefits.

Fortunately, health benefits of vitamin D do not need to be traded off for skin protection. You can get adequate amounts (>= 100% of recommended daily intake measure, such as RDA or DV) of vitamin D from diet and/or supplements. A supplement pill works reasonably well and is easy to take. However, with some diligence, you can also obtain adequate amounts of vitamin D from food.

* DV is Daily Value, a measure developed by the Food and Drug Administration (FDA) to help consumers determine if a food contains a lot or a little of a specific nutrient. The DV for vitamin D is 400 IU (10 µg) for adults. The above data is from USDA Nutrient Database.

We should note that recent research indicates that intakes of vitamin D above the minimally adequate level (i.e. when blood level of 25-hydroxy vitamin D is at least in the middle of the normal range – but not exceeding the upper bound) may provide additional health and longevity benefits, including reduced risk of cancer and other diseases.

If you still prefer to get your vitamin D mainly via sun exposure, we recommend that you protect with your face and neck (the areas where the skin tends to age faster and more visibly), and expose unprotected hands, legs and/or back to the sun to the degree sufficient for adequate vitamin D synthesis as outlined above.

Sunlight (UV-light) and skin conditions

Certain inflammatory skin conditions, such as psoriasis and eczema, may respond to the treatment with ultraviolet radiation. In such a situation, it is up to you and your physician to assess all the risk and benefits of using UV-light as a therapeutic alternative.

Daylight and the regulation of mood and body cycles

In some people, lack of exposure to bright light may disturb normal sleep-wake cycle leading to insomnia and depression. This has to do with the effect of light on the production of certain brain chemicals, such as serotonin and melatonin.

However, these effects result from the lack of exposure of your eyes to bright visible light -- they are not caused by the lack of the skin exposure to UV radiation. With proper protection (sunscreens, clothing, UVA+UVB blocking windows, UVA+UVB blocking eye-glasses, etc.) you can receive sufficient daylight exposure without the associated skin damage.

Other benefits of sunlight (UV light)

Some people feel that sunlight provides benefits beyond improving one's vitamin D status or normalizing sleep-wake cycle. In particular, some claim they feel energized after spending some time in the sun or that they get fewer colds. However, correlation is not causation – these effects, even if real, may be caused by simply spending time outdoors or the concomitant physical exercise. While it is conceivable that UV radiation has additional so-far-unknown health benefits, this remain to be backed by evidence. On the other hand, the negative effects of UV are well established. As mentioned above, if you still wish to get direct sun exposure, we recommend that you protect with your face and neck, and expose unprotected hands, legs and/or back to a modest degree. And make sure your dermatologist checks your skin regularly.