Effect of increased intake of skimmed milk, casein, whey or water on body composition and leptin in overweight adolescents: a randomized trial.

BACKGROUNDS: Dairy proteins may support muscle protein synthesis and improve satiety in adults. However, there are limited studies using exact measures of body composition, especially in adolescents. OBJECTIVES: This study investigates the effect of milk proteins and water on body composition and leptin in overweight adolescents. METHODS: Subjects (n = 193) aged 12-15 years were randomized to drink 1 L d(-1) of skimmed milk, whey, casein (all milk-based drinks 35 g protein L(-1) ) or water for 12 weeks. Twenty participants dropped out. A pre-test control group of 32 adolescents was examined 12 weeks before start of intervention. Outcomes included leptin and dual-energy X-ray absorptiometry scanning. The effects of the milk-based drinks on body composition and leptin were compared with baseline, pre-test control and water. RESULTS: Lean mass index (LMI) increased compared to baseline (all 95% confidence intervals 0.05-0.50 kg m(-2) , all P ≤ 0.009) and the pre-test control group (0.044-0.247 kg m(-2) , P ≤ 0.002) for all four test drinks. Fat mass index (FMI) increased only for milk-based drink groups compared with baseline (0.15-0.67 kg m(-2) , P < 0.001) and also compared with water (0.029-0.255 kg m(-2) , P ≤ 0.011). For pre-test control, there was no change in FMI or LMI. Leptin increased in the casein (1.016-3.246 ng mL(-1) , P < 0.001; 0.952-3.294 ng mL(-1) , P < 0.001) and whey groups (0.135-2.273 ng mL(-1) , P = 0.027; 0.069-2.322, P = 0.038) compared with water and pre-test control group, respectively. CONCLUSIONS: Although milk proteins increased LMI in overweight adolescents, there was a concurrent increase in FMI and leptin, whereas water only resulted in increased LMI. Thus, increased water intake may be beneficial for body composition in overweight adolescents.

Associations between vitamin D status in infants and blood lipids, body mass index and waist circumference.

AIM: To study the relationships between 25-hydroxyvitamin D status and blood lipids, insulin, glucose, body mass index and waist circumference in infants. METHODS: In a cross-sectional study, 255 infants aged 9 months with a blood sample for 25-hydroxyvitamin D were examined. Plasma 25-hydroxyvitamin D concentrations were analysed by chemiluminescent immunoassay. Associations between plasma 25-hydroxyvitamin D and high-density lipoprotein (HDL), low-density lipoprotein, total cholesterol, triglycerides, insulin, glucose, body mass index and waist circumference were analysed. RESULTS: Mean plasma 25-hydroxyvitamin D was 77.2 ± 22.7 nM. At the time of examination, 97% received vitamin D supplementation. 25-Hydroxyvitamin D was negatively associated with HDL (p = 0.003), cholesterol (p = 0.002) and triglycerides (p = 0.010) in multivariate analysis controlled for gender, season, body mass index, length, birth weight and breastfeeding. There were no associations between 25-hydroxyvitamin D and glucose or insulin (all p > 0.05). 25-hydroxyvitamin D was negatively associated with body mass index (p = 0.005) and waist circumference (p = 0.002) controlled for gender, season, breastfeeding, birth weight and length. CONCLUSION: Vitamin D status is negatively associated with blood lipids, body mass index and waist circumference in infants where nearly all received vitamin D supplements. Whether this has long-term health effects remains to be elucidated.

Vitamin D status in infants: relation to nutrition and season.

In a cross-sectional study, the primary objective was to assess the plasma concentration of 25-hydroxyvitamin D (25(OH)D) in healthy 9-month-old infants (n=255). The secondary objective was to evaluate nutritional variables and season in relation to 25(OH)D. The concentration of 25(OH)D was 77.2 ± 22.7 nmol/l (mean ± s.d.), ranging from 12 to 151 nmol/l. During the first 9 months, 97% received vitamin D supplementation (10 µg/day) and 89% had sufficient levels of 25(OH)D (50-250 nmol/l). In multiple regression analysis, controlled for body mass index (BMI) and intake of infant formula, a longer period of exclusive breastfeeding (P=0.026) and breastfeeding at 9 months (P=0.001) were both associated with lower levels. Dietary vitamin D intake was 4.4 ± 3.1 µg/day and in multiple regression analysis, controlled for BMI, intake of infant formula and mean energy intake, it was positively associated with 25(OH)D (P=0.001). There was a significant seasonal difference in 25(OH)D, with higher levels during summer-autumn compared with winter-spring (P=0.021) after control for BMI.