Causal link between vitamin D deficiency and ill health still possible

The two BMJ articles suggest that vitamin D supplementation has limited benefits.1 2 However, their findings could be compromised by non-adjustment for several factors—inclusion of the same study data in several meta-analyses reviewed; benefits only at higher intakes (fracture reduction in older women) or with baseline deficiency (muscle strength); “thresholds” for detectable benefits (insulin resistance when final 25 hydroxyvitamin D ≥80 nmol/L); and non-exclusion …