Vitamin D and Health

9.12 Bone health was selected by the IOM as the basis for setting an EAR and RDA for vitamin D for all life
stage groups, except infants where an AI was specified. Evidence for other health outcomes was not
considered sufficient to inform the DRIs. Conclusions in relation to serum 25(OH)D concentrations
and bone health were that the data, overall, suggested that a serum 25(OH)D concentration
< 30 nmol/L was associated with: increased risk of rickets, impaired fractional calcium absorption and
decreased BMC in children and adolescents, impaired fetal skeletal outcomes, impaired fractional
calcium absorption and an increased risk of osteomalacia in young and middle-aged adults and
impaired fractional calcium absorption and fracture risk in older adults. A serum concentration of
30 nmol/L was considered to be consistent with the lower end of requirements. It was also concluded
that there was a trend for maximal calcium absorption at serum concentrations of 50 nmol/L and little
causal evidence for additional benefits on BMD, fracture risk or osteomalacia risk at serum 25(OH)D
concentrations > 50 nmol/L.
9.13 Using the range of 30-50 nmol/L to capture the distribution of vitamin D requirements for bone
health, a serum 25(OH)D concentration of 40 nmol/L was considered to be consistent with the median
dietary requirement and this concentration was used to establish the EAR intake value for vitamin D as
it covered half the population's needs. By convention, adding two SDs to the average requirement
would cover the needs of 97.5% of the population: therefore using 40 nmol/L as the average
requirement, 50 nmol/L would cover the needs of most individuals in terms of vitamin D and this was
used to establish the RDA intake value for vitamin D.
9.14 The considerations in the current review agree with the IOM in terms of selecting rickets and
osteomalacia as the basis for developing DRVs. However, evidence on BMC and fracture risk was
considered insufficient to inform the setting of DRVs and calcium absorption was not considered as a
health outcome but as an intermediate factor affecting bone health. Evidence on falls and muscle
strength and function (which were not used by the IOM in the development of DRIs) has strengthened
since publication of the IOM report and these additional outcomes are used here to inform the setting
of the DRVs for vitamin D.
9.15 In the current review, the data were not considered sufficient to establish a distribution of serum
25(OH)D concentrations that would be necessary for estimating the distribution of requirements for
vitamin D intake (i.e., LRNI, EAR, RNI). The threshold serum 25(OH)D concentration of 25 nmol/L was
therefore selected as indicative of the serum 25(OH)D concentration below which risk of poor
musculoskeletal health is increased. Since it represents the concentration that the majority of the
population (about 97.5%) should be above in terms of protecting musculoskeletal health, it
corresponds to an RNI-type value. This approach differs from that used by the IOM in selecting a
serum 25(OH)D concentration of 50 nmol/L as being consistent with an RDA-type value (i.e., covering
the needs of 97.5% of the population).
Modelling exercise
9.16 Two modelling options for attaining year-round serum 25(OH)D concentration ≥ 25 nmol/L were
investigated:
the summer sunshine exposure required to maintain serum concentration ≥ 25 nmol/L during
winter (i.e., current DH, 1991 approach);
the intake of vitamin D, assuming minimal sun availability throughout the year (as per winter),
required to maintain serum 25(OH)D concentration ≥ 25 nmol/L.
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