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Evidence strengthened·Grade A·4 min read·reviewed 2026-06-01

The Sun Paradox: why men in the brightest cities run low on vitamin D

Dubai and Chennai get 3,000+ hours of sun a year. Their office workers still show widespread deficiency. Here is the mechanism — and the sane response.

The Sun Paradox: why men in the brightest cities run low on vitamin D

the one-line answer

Sun through glass does not make vitamin D. If your week is indoors, ask a clinician whether a test makes sense — then act on the result, not a guess.

What is going on

Vitamin D is synthesized in skin by direct UVB exposure. Office towers, car commutes, covered clothing and glass windows all block it. Studies across Gulf and Indian urban populations consistently find high insufficiency rates despite the sunshine outside the window.

How strong is the evidence

Grade A. The physiology is textbook, population surveys are consistent, and public-health guidance from NIH ODS and regional authorities aligns. What is NOT established: that supplementing without testing helps people with normal levels.

What to actually do

First, food: oily fish, fortified milk, egg yolks. Second, sensible direct sun where your skin and climate allow. Third, if your routine is indoor-heavy, ask a clinician whether a test is appropriate. Supplement decisions follow the test — not the other way around.

Who should not self-prescribe

Anyone with kidney disease, a history of stones, abnormal calcium, or relevant medicines. Vitamin D is fat-soluble and excess is genuinely harmful.

sources

  • NIH ODS Vitamin D Fact Sheet (S04)

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General wellbeing information only — not medical advice, diagnosis, or treatment. Supplements can cause side effects and interact with medicines. Check with a qualified doctor, dietitian, or pharmacist if you have symptoms, a health condition, take medicine, are preparing for surgery, or are unsure.

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