The worthlessness of Vitamin D is mildly exaggerated
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Vitamin D skepticism may be overdone; low levels likely warrant supplementation.
The author challenges the prevailing view that vitamin D supplements are worthless except for severe deficiency. While large RCTs like WHI (400 IU) and VITAL (2000 IU) showed modest, mostly non-significant benefits, the author argues biology supports a different picture: vitamin D receptors exist in almost all cells, and many tissues locally convert storage vitamin D to active form. This suggests low storage levels (25-50 nmol/L) could impair local signaling even when kidney function is normal. The author concludes supplementation for those with low-ish levels is a reasonable bet, not a proven cure.
The article reviews the history from rickets to correlations with cancer and all-cause mortality, then notes RCTs have dampened enthusiasm but may have used insufficient doses or failed to target deficient populations.
What commenters are saying
Top comment notes sunlight's benefits may come from nitric oxide and red light effects, not just vitamin D. Several commenters report personal benefits from supplementation, especially when deficient. A counter-camp argues vitamin D is primarily a marker for outdoor exercise. One commenter warns that over-supplementation is now more common than deficiency in their doctor's practice, and advises blood testing. Another notes darker-skinned individuals may need more sun exposure but more research is needed.