Effects of high dairy protein intake and vitamin D supplementation on body composition and cardiometabolic markers in 6-8-y-old children-the D-pro trial

Background Increasing evidence suggests that prevention of lifestyle diseases should begin early. Dairy protein and vitamin D can affect body composition and cardiometabolic markers, yet evidence among well-nourished children is sparse. Objectives We investigated combined and separate effects of high dairy protein intake and vitamin D on body composition and cardiometabolic markers in children. Methods In a 2 x 2-factorial, randomized trial, 200 white, Danish, 6-8-y-old children substituted 260 g/d dairy in their diet with high-protein (HP; 10 g protein/100 g) or normal-protein (NP; 3.5 g protein/100 g) yogurt and received blinded tablets with 20 mu g/d vitamin D-3 or placebo for 24 wk during winter. We measured body composition (by DXA), blood pressure, and fasting blood glucose, insulin, C-peptide, and lipids. Results In total, 184 children (92%) completed the study. Baseline median (25th-75th percentile) dairy protein intake was median: 3.7 (25th-75th percentile: 2.5-5.1) energy percentage (E%) and increased to median: 7.2 (25th-75th percentile: 4.7-8.8) E% and median: 4.2 (25th-75th percentile: 3.1-5.3) E% with HP and NP. Mean +/- SD serum 25-hydroxyvitamin D concentration changed from 81 +/- 17 to 89 +/- 18 nmol/L and 48 +/- 13 nmol/L with vitamin D and placebo, respectively. There were no combined effects of dairy protein and vitamin D, except for plasma glucose, with the largest increase in the NP-vitamin D group (P-interaction = 0.005). There were smaller increases in fat mass index (P = 0.04) with HP than with NP, and the same pattern was seen for insulin, HOMA-IR, and C-peptide (all P = 0.06). LDL cholesterol was reduced with vitamin D compared with placebo (P < 0.05). Fat-free mass and blood pressure were unaffected. Conclusions High compared with normal dairy protein intake hampered an increase in fat mass index. Vitamin D supplementation counteracted the winter decline in 25-hydroxyvitamin D and the increase in LDL cholesterol observed with placebo. This study adds to the sparse evidence on dairy protein in well-nourished children and supports a vitamin D intake of similar to 20 mu g/d during winter. This trial was registered at clinicaltrials.gov as NCT03956732.

Automated summary

This study investigated the combined and separate effects of high dairy protein intake and vitamin D on body composition and cardiometabolic markers in children. The study found that high dairy protein intake inhibited an increase in fat mass index, while vitamin D supplementation counteracted the winter decline in 25-hydroxyvitamin D and the increase in LDL cholesterol.