Your body can produce vitamin D when the skin is exposed to ultraviolet B (UVB) rays.^[1] Yet it is these rays that sunscreens are designed to primarily block.^[2] So will using sunscreen tank your vitamin D levels?

Sunscreen and vitamin D production

Sunscreen can decrease vitamin D production under both controlled laboratory testing and real-world conditions.^[3][4] This decrease is most notable if sunscreen is used consistently and properly (i.e., when using a broad-spectrum sunscreen, the right sun protection factor (SPF), amount, and reapplication schedule).^[5][6][7]

Yet, the amount to which sunscreen decreases vitamin D production appears to be small — a counterintuitive finding.^[8] How could this be? Two factors have been proposed as possible explanations:^[8]

1. People may not be appropriately using sunscreen during periods of sun exposure (i.e., incorrect type, amount, SPF, or application frequency). If not used correctly, UVB rays could easily reach areas of your skin where sunscreen is absent or where coverage is not sufficient enough.

2. While sunscreen does a good job of blocking most UVB rays, it doesn’t entirely block them. A high amount of exposure to UVB rays is not required to kickstart vitamin D production in the skin. So, it’s possible that low amounts of UVB radiation could get past the sunscreen to initiate vitamin D creation.

One important caveat — studies to date have generally been conducted on people with less skin pigmentation (i.e., those with Fitzpatrick skin types 1–3). A different result may be seen in those with Fitzpatrick skin types 4–6.