How sunlight helps make vitamin D
When ultraviolet B (UVB) rays reach skin, they trigger a chemical change in a cholesterol-like substance there. The body then processes the resulting compound into vitamin D. Sunscreen is designed to absorb or reflect some UV radiation, so, in theory, applying it perfectly over every exposed area can reduce this production.
Why sunscreen usually isn’t the cause of low vitamin D
That theoretical effect does not translate neatly to everyday life. Sunscreen is rarely applied as thickly or as evenly as it is in controlled tests, and people spend time outdoors with some skin uncovered. Research in real-world conditions has generally not found that routine sunscreen use causes vitamin D deficiency.
Vitamin D levels also depend on factors such as diet, skin pigmentation, age, season, and how much time someone spends outdoors. A low level cannot be blamed on sunscreen alone—and skipping sunscreen is not a reliable way to fix it.
Protect skin without guessing at your vitamin D level
UV radiation also damages skin and raises the risk of skin cancer. Public health guidance therefore does not recommend getting unprotected sun exposure as a vitamin D strategy. Food and supplements can provide vitamin D without that UV damage; a clinician can advise whether testing or a supplement makes sense, especially for someone at higher risk of deficiency.
The practical tradeoff is not sunscreen versus vitamin D: protect your skin outdoors, and address vitamin D through diet or medical advice if there is a reason to be concerned.
