The need for sunscreen is undisputed: Adequate SPF minimizes the skin’s exposure to cancer- and wrinkle-causing UV radiation. Also important is the body’s requirement for vitamin D, as it contributes to healthier teeth and bones, reduced inflammation, and improved immune function in the skin. But is the controversy surrounding sunscreen and its role in blocking vitamin D production a valid one?
As medical options for testing levels of vitamin D have become more advanced and accessible, doctors are better able to determine a patient’s vitamin D level, and frequent lower-than-average test results have put a public spotlight on vitamin D deficiency. The resulting search for a simple, concrete explanation has led to finger-pointing at sunscreen when in fact, the answer is much more complex.
First, it’s important to understand what vitamin D does and how our bodies produce it. Vitamin D’s most important contribution is to bone health, especially in adult women and children. Vitamin D deficiency has been linked to bone abnormalities such as osteomalacia in adults, and to a condition called rickets in children.
In the skin, vitamin D also affects the way that keratinocytes grow and can slow the growth of abnormal skin cells in conditions like psoriasis. Vitamin D improves the skin’s immune function, in turn decreasing inflammation. Furthermore, investigations are currently underway to determine if vitamin D may reduce the formation of non-melanoma skin cancers.
Vitamin D synthesis begins with two inactive precursors: D2, obtained via diet; and D3, through sun exposure. These precursors undergo further conversion in the liver before transforming in the kidneys to the active form of vitamin D.
Here’s where sunscreen comes into play: Sunscreens act by blocking UVB rays, which in turn decreases the availability of these rays to stimulate the production of the D3 precursor.
Even without sunscreen, the skin’s ability to generate vitamin D precursors is actually quite limited. After 20 minutes of sun exposure to less than 10 percent of the body surface, the skin's ability to convert Vitamin D maxes out for the day.
While the jury is out on exactly all the reasons vitamin D levels may be below normal, we do know that sunscreens lead to a reduction in sun damage and skin cancer. Minimal exposure to UV radiation is necessary to prevent skin cancer, wrinkles and other visible signs of sun damage that occur over time, such as volume loss, sagging, and hyperpigmentation.
The best sources of vitamin D can be found in the diet: fatty fish such as salmon, eggs, fortified milk and cereals. In fact, the American Academy of Dermatology (AAD) recommends that sufficient levels can be obtained through supplements or a diet rich in natural or fortified sources of vitamin D.
The AAD also states that unprotected UV exposure is not a safe method by which to obtain vitamin D. According to the Academy, “While UV radiation is one source of vitamin D, dermatologists argue that it is not the best source because the benefits of obtaining vitamin D through UV exposure cannot be separated from an increased risk of skin cancer.”
So does sunscreen block vitamin D production? Yes, but not enough to significantly impact vitamin D levels—and the benefits of wearing sunscreen far outweigh any perceived risk of inadequate vitamin D.
This means that patients can sun safely—by applying broad spectrum sunscreen, minimizing or altogether avoiding sun exposure, and wearing sun-protective clothing—without concerns of vitamin D deficiency.