Vitamin D for Osteoporosis
Vitamin D is essential for calcium absorption and bone health, but on its own it does not prevent fractures; a modest reduction in hip fractures appears only when it is combined with calcium, and even that benefit is inconsistent across recent trials.
Why this grade7-layer evidence engine
This earns a Preliminary (B) grade because the evidence is real but conditional. Four meta-analyses agree that vitamin D taken alone gives no fracture protection: a 2024 analysis of nearly 72,000 older adults found no benefit for total fractures (RR 1.03) and even a higher hip-fracture risk in women (RR 1.34) [PMID 38997531], and a large 2019 JAMA Network Open review echoed this for vitamin D alone (RR 1.06 any fracture) [PMID 31860103].
The benefit that does exist comes from combining vitamin D with calcium. The 2019 review found the combined regimen cut hip fractures by about 16% (RR 0.84), and a 2020 review reported higher bone density and fewer hip fractures (RR 0.86) [PMID 33237064, PMID 31860103]. However, a 2023 meta-analysis of 18 trials found no significant fracture reduction for either nutrient alone or combined (hip RR 1.56, not significant) [PMID 37602580], so results are not uniform.
Regulators and clinics support vitamin D as foundational rather than curative. The FDA recognizes vitamin D3 as safe (GRAS) and EFSA confirms an established role in bone health, while Mayo, Cleveland Clinic, Harvard, and the Bone Health & Osteoporosis Foundation all back roughly 800-1,000 IU daily for calcium absorption and slowing bone loss. Harvard cautions that doses above 4,000 IU/day may harm bone density, so more is not better.
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.67
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 positive (2 篇 > 1 negative)
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status