Evidence-based articles about vitamin D, sun exposure, and health optimization.
35 articles
Low vitamin D levels appear repeatedly in autoimmune conditions from MS to rheumatoid arthritis. Here's what trials and large cohort studies actually show — and what remains unresolved.
Sun and supplements both raise 25(OH)D, but the speed and ceiling differ. Here's what the evidence says about which works faster and when each has the edge.
UV index alone won't tell you how long to stay outside for vitamin D. Your skin's melanin content can shift the required exposure time by 300–500%. Here's the science.
UV index tells you whether your body can make vitamin D right now — but location and season determine whether that window even opens. Here's the science.
At latitudes above 35°N, winter UVB vanishes for months. Here's how to know when sun exposure stops working — and what to do instead.
Six years of NYC weather data show Friday as the rainiest weekday. We unpack the storm-track theory, pollution lag, and what lost sun means for vitamin D.
Altitude amplifies UV radiation faster than most people expect. Here's how elevation changes your vitamin D sun window and what that means for your skin.
UV index is the missing link between sun exposure and vitamin D synthesis. Here's what the number actually tells you — and when supplements fill the gap.
UV index tells you whether vitamin D synthesis is even possible today — and how to adjust your time outside based on skin tone, season, and location.
UV index varies dramatically by location, season, and altitude. Here's how each factor shifts your vitamin D sun window and what to do when your location works against you.