Vitamin D and Health

6.22 Interpretation of bone health indices such as BMD and BMC in children is less clear. BMD is a less
informative measure of bone health than BMC because BMD partially corrects for attained size and
therefore dilutes any possible relationships with skeletal growth. The International Society for Clinical
Densitometry (ISCD) has published guidelines for clinical assessment of bone in children (Bishop et al.,
2014; Crabtree et al., 2014).
6.23 Biochemical markers associated with bone formation and resorption have also been used to assess
bone health. Serum concentrations of osteocalcin, procollagen carboxy peptide, procollagen amino
peptide and bone-specific alkaline phosphatase are validated indices of bone formation (DH, 1998).
Markers of bone resorption are based on breakdown products of type I collagen in serum or urine and
include pyridinium crosslinks of collagen (PYR and DPYR) and C-terminal crosslinks of type I collagen
(CTX). Limitations of current biochemical markers of bone metabolism include lack of tissue specificity
for bone and an inability to distinguish the metabolic activity of different skeletal compartments
(Garnero, 2014).
Consideration of the evidence on vitamin D and musculoskeletal health outcomes
6.24 Evidence on vitamin D and the following musculoskeletal health outcomes was considered: rickets,
osteomalacia, bone health indices (e.g., BMC, BMD, biochemical markers of bone turnover), fracture
prevention, risk of falls and muscle health (Tables 1-30, Annex 2).
6.25 Evidence on rickets and osteomalacia was not considered by life stage but separately, prior to
consideration of other musculoskeletal health outcomes. Data on musculoskeletal health outcomes
other than rickets and osteomalacia were considered by life stage (pregnancy & lactation, infants up
to 12m, children 1-3y, children 4-8y & adolescents 9-18y, adults < 50y and adults ≥ 50y) since different
musculoskeletal health outcomes are relevant to specific age groups. Evidence on vitamin D and bone
health indices was considered across all life stages; muscle strength and function and stress fracture
risk were considered in adults < 50y 39 ; fracture prevention, risk of falls and muscle strength and
function were considered in adults ≥ 50y.
Rickets
6.26 IOM Report: The IOM concluded that, overall, there was fair evidence for an association between low
serum 25(OH)D concentration and confirmed rickets but the evidence for a threshold serum 25(OH)D
concentration above which rickets did not occur was inconsistent. Thirteen studies were identified
which assessed the association between serum 25(OH)D concentration and rickets in infants and
young children (1 RCT; 4 before-after studies; 8 case-control studies) but it was noted that many were
from developing countries where calcium intake is low and could, therefore, be confounded by dietary
calcium.
6.27 Six studies (1 RCT; 3 before & after; 2 case-control) reported mean or median serum 25(OH)D
concentrations below 30 nmol/L in children with rickets; the remaining studies reported mean serum
25(OH)D concentration above 30 nmol/L (range 36-50 nmol/L).
6.28 The IOM concluded that if calcium intake was adequate, the risk of rickets was increased at serum
25(OH)D concentration < 30 nmol/L.
39 Ages ranged from 16 to 35 years in the studies considered.
45