Vitamin D and Health

according to whether immunoassay (~9 µg/360 IU) or LC-MS/MS analysis (12 µg/480 IU) is used, an
RNI of 10 µg/d (400 IU) was set between these two estimates.
RNIs for vitamin D by life-stage
9.42 The data used to estimate the vitamin D intake required to achieve a serum 25(OH)D concentration
≥ 25 nmol/L were drawn from individual RCTs in adults aged 20-40y, adults aged ≥ 64y and adolescent
girls aged 11y. Dose-response data were not available to allow direct determination of the vitamin D
intake needed to achieve a serum 25(OH)D concentration ≥ 25 nmol/L in infants and children aged 0-
10y or during pregnancy and lactation. However, the IOM did not find an age-dependent effect of
vitamin D supplementation dose (but noted that this finding was based on a limited amount of data).
A subsequent Danish RCT (Madsen et al., 2013) examining the effects of vitamin D fortified milk and
bread on serum 25(OH)D concentrations of children and adults (n=782), reported no difference in
treatment effects by age group (4-10, 11-17, 18-40 and 41-60y). This suggests that data from the RCTs
in adults (20-40y and ≥ 64y) and adolescent girls (aged 11y) can be extrapolated to younger age
groups.
9.43 The RNI estimates for vitamin D assume that calcium intakes are adequate. However, findings from an
RCT (Cashman et al., 2014a) indicate that calcium intake does not modify the requirement for vitamin
D in healthy adults with intakes ranging from low (496 mg/d) to high (1437 mg/d) (see paragraph
2.75). These findings may not be applicable to children (who have higher calcium requirements
because of increased metabolism) or in patients with metabolic bone disease.
UK general population aged 11y and above
9.44 An RNI of 10 µg/d (400 IU) of vitamin D is proposed for the UK general population aged 11y and
above. This is the average vitamin D intake (from natural food sources, fortified food or supplements)
needed to achieve a serum 25(OH)D concentration ≥ 25 nmol/L during winter in 97.5% of the
population. It refers to the average vitamin D intake over a period of time (e.g., 1 week) and takes
account of day to day variations in intake.
9.45 The RNI assumes minimal sunshine exposure because the studies used to derive this figure were
carried out in winter.
9.46 Although most people would be expected to synthesise vitamin D and naturally achieve a serum
25(OH)D concentration ≥ 25 nmol/L during the summer due to sun exposure, the NDNS and other
studies indicate that a substantial proportion (7-53%) of some population groups in the UK have a
serum 25(OH)D concentration < 25 nmol/L in the summer. Since it is not possible to identify these
individuals, it is proposed that the RNI should apply throughout the year. This is a precautionary
approach to protect population groups and individuals with sustained serum 25(OH)D concentration
< 25 nmol/L and to take account of variable exposure to sunshine and diet. It ensures coverage of
97.5% of the population throughout the year.
Pregnancy and lactation
9.47 Data are not available to suggest the requirement for an additional increment during pregnancy and
lactation. Therefore, the RNI proposed for the general UK population (10 µg or 400 IU/d) is also
applicable to pregnant and lactating women.
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