Vitamin D and Health

thresholds, although there has also been disagreement over the appropriate threshold concentration
for a specific functional endpoint(s).
4.29 In the UK, for example, a serum 25(OH)D concentration of 25 nmol/L is currently used as a threshold
(cut-off) for defining the lower limit of adequacy (DH, 1998), based on evidence suggesting risk of
rickets and osteomalacia is increased at concentrations below this level.
4.30 The IOM, using bone health as the basis for developing Dietary Reference Intakes (DRIs) for vitamin D,
proposed a serum 25(OH)D concentration of 40 nmol/L as the value above which approximately half
the population might meet its vitamin D requirement (in terms of bone health and below which half
might not) and 50 nmol/L as the concentration that would meet the requirement of nearly all (i.e.,
97.5%) ‘normal healthy persons’. The IOM DRI committee also concluded that: individuals are at risk
of deficiency at serum 25(OH)D concentrations < 30 nmol/L; some, but not all, individuals are
potentially at risk for inadequacy at serum 25(OH)D concentrations from 30 up to 50 nmol/L; and
practically all individuals are sufficient at concentrations of 50 nmol/L and above.
4.31 In contrast, the Endocrine Society Task Force on Vitamin D (Holick et al., 2011) concluded that
‘individuals should be identified as vitamin-D-deficient at a cut-off level of 50 nmol/L serum 25(OH)D’
and ‘to maximise the effect of vitamin D on calcium, bone, and muscle metabolism’, serum 25(OH)D
concentration ‘should exceed 75 nmol/L’.
4.32 While both the IOM DRI committee and the Endocrine Society Task Force appeared to agree that
there was insufficient evidence of a causative link between 25(OH)D concentration and any nonskeletal
disease outcomes, others have proposed serum 25(OH)D thresholds between 50-120 nmol/L
to reduce the risk of adverse non-skeletal outcomes (Zittermann, 2003; Holick, 2004b).
4.33 The wide variation in measurements of serum 25(OH)D concentration, made using different methods
and in different laboratories, should be taken into account in the interpretation of studies that have
examined the relationship between serum 25(OH)D concentration and health outcomes.
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