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 × 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 µg/d vitamin D3 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 (Pinteraction = 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 ∼20 µg/d during winter. This trial was registered at clinicaltrials.gov as NCT03956732.

Effects of vitamin D and high dairy protein intake on bone mineralization and linear growth in 6- to 8-year-old children: the D-pro randomized trial

BACKGROUND

Vitamin D and dairy protein may stimulate bone mineralization and linear growth in children, but previous studies show inconsistent results and have not examined their combined effects.

OBJECTIVES

To investigate combined and separate effects of vitamin D supplementation and high-protein (HP) compared with normal-protein (NP) yogurt intake on children's bone mineralization and linear growth.

METHODS

In a 2 × 2-factorial trial, 200 healthy, 6- to 8-year-old, Danish, children with light skin (55°N) were randomized to 20 µg/d vitamin D3 or placebo and to substitute 260 g/d dairy with HP (10 g protein/100 g) or NP (3.5 g protein/100 g) yogurt for 24 weeks during an extended winter. Outcomes were total body less head (TBLH) and lumbar spine bone mineral density (BMD), bone mineral content (BMC), and bone area (BA) by dual-energy X-ray absorptiometry, height, and biomarkers of bone turnover and growth. The primary outcome was TBLH BMD.

RESULTS

In total, 184 children (92%) completed the study. The baseline serum 25-hydroxyvitamin D was 80.8 ± 17.2 nmol/L, which increased by 7.2 ± 14.1 nmol/L and decreased by 32.3 ± 17.5 nmol/L with vitamin D and placebo, respectively. The baseline protein intake was 15.4 ± 2.4 energy percentage (E%), which increased to 18.3 ± 3.4 E% with HP. There were no vitamin D-yogurt interactions and no main effects of either intervention on TBLH BMD. However, vitamin D supplementation increased lumbar spine BMD and TBLH BMC compared to placebo, whereas HP groups showed lower increments in lumbar spine BMD, TBLH BMC and BA, and plasma osteocalcin compared to NP groups. Height, growth factors, and parathyroid hormone levels were unaffected.

CONCLUSIONS

Although there were no effects on whole-body BMD, vitamin D increased bone mass and spinal BMD, whereas high compared with normal dairy protein intake had smaller incremental effects on these outcomes. This supports a recommended vitamin D intake of around 20 µg/d during winter but not use of HP dairy products for improved bone mineralization among healthy, well-nourished children. This trial was registered at clinicaltrials.gov as NCT03956732.

Changes in metabolism but not myocellular signaling by training with CHO-restriction in endurance athletes

Carbohydrate (CHO) restricted training has been shown to increase the acute training response, whereas less is known about the acute effects after repeated CHO restricted training. On two occasions, the acute responses to CHO restriction were examined in endurance athletes. Study 1 examined cellular signaling and metabolic responses after seven training-days including CHO manipulation (n = 16). The protocol consisted of 1 h high-intensity cycling, followed by 7 h recovery, and 2 h of moderate-intensity exercise (120SS). Athletes were randomly assigned to low (LCHO: 80 g) or high (HCHO: 415 g) CHO during recovery and the 120SS. Study 2 examined unaccustomed exposure to the same training protocol (n = 12). In Study 1, muscle biopsies were obtained at rest and 1 h after 120SS, and blood samples drawn during the 120SS. In Study 2, substrate oxidation and plasma glucagon were determined. In Study 1, plasma insulin and proinsulin C-peptide were higher during the 120SS in HCHO compared to LCHO (insulin: 0 min: +37%; 60 min: +135%; 120 min: +357%, P = 0.05; proinsulin C-peptide: 0 min: +32%; 60 min: +52%; 120 min: +79%, P = 0.02), whereas plasma cholesterol was higher in LCHO (+15-17%, P = 0.03). Myocellular signaling did not differ between groups. p-AMPK and p-ACC were increased after 120SS (+35%, P = 0.03; +59%, P = 0.0004, respectively), with no alterations in p-p38, p-53, or p-CREB. In Study 2, glucagon and fat oxidation were higher in LCHO compared to HCHO during the 120SS (+26-40%, P = 0.03; +44-76%, P = 0.01 respectively). In conclusion, the clear respiratory and hematological effects of CHO restricted training were not translated into superior myocellular signaling after accustomization to CHO restriction.

Ten weeks of aerobic training does not result in persistent changes in VLDL triglyceride turnover or oxidation in healthy men

OBJECTIVE

Very low density lipoprotein triglyceride (VLDL-TG) and free fatty acids (FFA) constitute a substantial proportion of human energy supply both at rest and during exercise. Exercise acutely decreases VLDL-TG concentration, and VLDL-TG clearance is increased after an exercise bout. However, the effects of long-term training are not clear.

DESIGN

The aim was to investigate long-term effects of training by direct assessments of VLDL-TG and palmitate kinetics and oxidation in healthy lean men (n=9) at rest, before and after a 10-week training program, compared with a non-training control group (n=9).

METHODS

VLDL-TG kinetics were assessed by a primed constant infusion of [1-14C]VLDL-TG, and VLDL-TG oxidation by specific activity (14CO2) in expired air. The metabolic study days were placed 60-72 h after the last exercise bout.

RESULTS

Palmitate kinetics and oxidation were assessed by a 2 h constant infusion of [9,10-(3)H]palmitate. In the training group (n=9), maximal oxygen uptake increased significantly by ≈20% (P<0.05), and the insulin sensitivity (assessed by the hyperinsulinemic-euglycemic clamp) improved significantly (P<0.05). Despite these metabolic improvements, no changes were observed in VLDL-TG secretion, clearance, or oxidation or in palmitate kinetics.

CONCLUSION

We conclude that 10 weeks of exercise training did not induce changes in VLDL-TG and palmitate kinetics in healthy lean men.

Erythropoietin administration alone or in combination with endurance training affects neither skeletal muscle morphology nor angiogenesis in healthy young men

The aim was to investigate the ability of an erythropoiesis-stimulating agent (ESA), alone or in combination with endurance training, to induce changes in human skeletal muscle fibre and vascular morphology. In a comparative study, 36 healthy untrained men were randomly dispersed into the following four groups: sedentary-placebo (SP, n = 9); sedentary-ESA (SE, n = 9); training-placebo (TP, n = 10); or training-ESA (TE, n = 8). The ESA or placebo was injected once weekly. Training consisted of progressive bicycling three times per week for 10 weeks. Before and after the intervention period, muscle biopsies and magnetic resonance images were collected from the thigh muscles, blood was collected, body composition measured and endurance exercise performance evaluated. The ESA treatment (SE and TE) led to elevated haematocrit, and both ESA treatment and training (SE, TP and TE) increased maximal O2 uptake. With regard to skeletal muscle morphology, TP alone exhibited increases in whole-muscle cross-sectional area and fibre diameter of all fibre types. Also exclusively for TP was an increase in type IIa fibres and a corresponding decrease in type IIx fibres. Furthermore, an overall training effect (TP and TE) was statistically demonstrated in whole-muscle cross-sectional area, muscle fibre diameter and type IIa and type IIx fibre distribution. With regard to muscle vascular morphology, TP and TE both promoted a rise in capillary to muscle fibre ratio, with no differences between the two groups. There were no effects of ESA treatment on any of the muscle morphological parameters. Despite the haematopoietic effects of ESA, we provide novel evidence that endurance training rather than ESA treatment induces adaptational changes in angiogenesis and muscle morphology.

Whole body metabolic effects of prolonged endurance training in combination with erythropoietin treatment in humans: a randomized placebo controlled trial

Erythropoietin (Epo) administration improves aerobic exercise capacity and insulin sensitivity in renal patients and also increases resting energy expenditure (REE). Similar effects are observed in response to endurance training. The aim was to compare the effects of endurance training with erythropoiesis-stimulating agent (ESA) treatment in healthy humans. Thirty-six healthy untrained men were randomized to 10 wk of either: 1) placebo (n = 9), 2) ESA (n = 9), 3) endurance training (n = 10), or 4) ESA and endurance training (n = 8). In a single-blinded design, ESA/placebo was injected one time weekly. Training consisted of biking for 1 h at 65% of wattmax three times per week. Measurements performed before and after the intervention were as follows: body composition, maximal oxygen uptake, insulin sensitivity, REE, and palmitate turnover. Uncoupling protein 2 (UCP2) mRNA levels were assessed in skeletal muscle. Fat mass decreased after training (P = 0.003), whereas ESA induced a small but significant increase in intrahepatic fat (P = 0.025). Serum free fatty acid (FFA) levels and palmitate turnover decreased significantly in response to training, whereas the opposite pattern was found after ESA. REE corrected for lean body mass increased in response to ESA and training, and muscle UCP2 mRNA levels increased after ESA (P = 0.035). Insulin sensitivity increased only after training (P = 0.011).

IN CONCLUSION

1) insulin sensitivity is not improved after ESA treatment despite improved exercise capacity, 2) the calorigenic effects of ESA may be related to increased UCP2 gene expression in skeletal muscle, and 3) training and ESA exert opposite effects on lipolysis under basal conditions, increased FFA levels and liver fat fraction was observed after ESA treatment.