Evidence-based articles about vitamin D, sun exposure, and health optimization.
80 articles
SPF 30 blocks most UVB — but real-world sunscreen use is messier than lab data suggests. Here's what the evidence actually shows about sunscreen and vitamin D.
Your UV index, latitude, season, and skin tone together determine whether you can make vitamin D outside today — and for how long. Here's how to calculate it.
UV index and vitamin D output don't scale in a straight line. Here's what the photochemistry and clinical data say about the real relationship.
Food alone rarely closes the vitamin D gap — and how much sun helps depends entirely on where you live. Here's what the evidence shows by latitude, season, and diet.
People with darker skin tones are 3–5 times more likely to be vitamin D deficient — not because of sun avoidance alone, but because melanin biology changes everything. Here's what the evidence shows.
Food provides a fraction of the vitamin D most adults need. Here's what the evidence shows about dietary ceilings, sun synthesis, and when supplements fill the gap.
Most vitamin D-rich foods deliver far less than a single sun session. Here's what the evidence says about dietary ceilings, food sources, and when diet simply isn't enough.
Low vitamin D appears repeatedly alongside hormonal imbalances — but the relationship with estrogen is more specific than most articles admit. Here's what the evidence actually shows.
Standing desks near windows feel healthier, but glass blocks UVB almost entirely. Here's what the evidence says about indoor light, vitamin D synthesis, and what actually works.
Athletes consistently test lower for vitamin D than non-athletes in controlled studies. Here's what randomized trials show about levels, muscle recovery, and injury risk.