Bone Abstracts

In Canada, and many other countries, a vitamin D supplement of 400 IU/day is recommended for breastfed infants and staple foods are fortified with vitamin D in accordance with public health policy for the primary prevention of rickets. Both vitamin D receptors and 1-alpha hydroxylase enzymes are expressed in human muscle, implicating vitamin D status and metabolism in growth and development. In a randomized dose response study of vitamin D supplementation (400, 800, 1200, or 1600 IU/day) in infants (n=132) from 1 to 12 mo of age, 98% achieved 50 nmol/l 25-hydroxyvitamin D. Infants that achieved vitamin D status above 75 nmol/l of 25-hydroxyvitamin D had elevated percent lean mass and reduced fat mass at 12 mo of age while accounting for sex, length and macronutrient intakes, compared to those below 75 nmol/l. Upon follow-up, fat mass remained lower at 3 y of age. In a subgroup analysis of infants with low vitamin D status below 50 nmol/l at inception (n=18), those who received 1200 IU/day of vitamin D demonstrated higher lean mass accretion from 1 to 3 mo of age compared to those receiving a dosage of 400 IU/day. In an ongoing randomized trial of 400 vs 1000 IU/day of vitamin D in infants born with low vitamin D status (<50 nmol/l 25-hydroxyvitamin D; n=87), whole body lean mass was higher at 6 mo of age in the group randomized to 1000 IU/day of vitamin D, while accounting for sex, season, skin pigmentation and gestational age at birth. Similarly, in children 2 through 8 y of age (n=51) randomized to consume milk products (yogurt beverage and cheese) fortified with vitamin D (300 IU/day) vs. control for 6 mo, percent change in lean mass was enhanced in the intervention group. These controlled studies in infants and young children offer high-level evidence that achievement of population targets for vitamin D intakes and status supports a lean body mass phenotype.

Disclosure: The author is in receipt of honoraria or consultation fees and grants/research supports as follows: Research grant funding from Dairy Farmers of Canada (2013–2017) under the Dairy Cluster Initiative (Agriculture and Agri-Food Canada, Dairy Commission, Dairy Farmers of Canada) and honoraria from Dairy Farmers of Canada for speaker fees in 2018.

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