Vitamin D and Skin Cancer: Finding the Balance

For most people, 5-15 minutes of incidental sun exposure on forearms and face, 2-3 times per week, is sufficient for adequate vitamin D production. This is the amount you get walking to your car, running errands, or sitting near a window — not deliberate sunbathing.

Factors that reduce vitamin D production from sun: darker skin (more melanin blocks UVB), higher latitude, winter months, morning/evening hours, sunscreen use (though in practice most people apply too little to fully block production).

The Endocrine Society recommends 600-1,000 IU daily for most adults and 1,500-2,000 IU for those at risk of deficiency. A simple blood test (25-hydroxyvitamin D) can measure your level. Optimal is generally 30-50 ng/mL.

Supplements are preferable to deliberate sun exposure when: you live above 37° latitude (roughly north of San Francisco or Athens), you have fair skin and high melanoma risk, you are over 65 (skin produces less vitamin D with age), or you have a personal or family history of skin cancer.

Tanning beds are not a medically recommended source of vitamin D. While they do trigger production, the UVA-heavy spectrum of most tanning beds is less efficient at producing vitamin D than natural sunlight — and far more damaging to DNA.

A 1,000 IU supplement costs about $0.03 per day. A tanning bed session costs $5-15 and increases melanoma risk with every visit. The cost-benefit analysis is not close.

In theory, perfect sunscreen application blocks UVB and reduces vitamin D synthesis. In practice, studies consistently show that regular sunscreen users do not have lower vitamin D levels than non-users. This is because no one applies sunscreen perfectly — enough UV gets through.

The AAD's position: use sunscreen. Get vitamin D from diet (fatty fish, fortified dairy, eggs) and supplements if needed. Do not use skin cancer risk as a reason to skip sun protection.

Vitamin D deficiency is real and worth addressing. But it is easily solved with an inexpensive daily supplement or 5-15 minutes of incidental sun exposure. It does not require prolonged sunbathing, tanning beds, or forgoing sunscreen.

If you are concerned about your vitamin D level, ask your doctor for a blood test. If you are concerned about your moles, use our ABCDE checker. Both are solvable problems — and one does not need to come at the expense of the other.