Vitamin D3 supplementation
Most adults are deficient. Linked to muscle function, bone health, fall prevention, and immune function.
Why
Vitamin D3 (cholecalciferol) is involved in calcium metabolism, neuromuscular function, and immune signalling. Northern-latitude residents and indoor workers are commonly deficient. Supplementation modestly reduces fall risk in older adults and improves muscle strength when starting from low baseline.
How it works
Hydroxylated to calcitriol, the active hormone that regulates calcium absorption, neuromuscular signalling, and ~200 immune-related genes.
Expected onset · 6–8 weeks; retest 25(OH)D after 8 weeks of consistent dosing
How to take
Dosage
1,000–2,000 IU daily for maintenance; higher doses (4,000+ IU) for documented deficiency under medical guidance.
Timing
With a fat-containing meal
On the label
D3 (cholecalciferol), not D2. Pair with K2 (MK-7) for calcium routing.
Safety
Markers this may influence
Evidence
Bischoff-Ferrari 2009 BMJ meta-analysis (8 RCTs, n=2,426 older adults): supplemental vitamin D 700–1000 IU/day reduced fall risk by ~19% (pooled RR 0.81). EFSA Reg 432/2012 authorises the claim that vitamin D contributes to normal muscle function and bones. Most adults at northern latitudes are deficient in winter.
Where to get it
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