Karina Arnberg

Skim Milk, Whey, and Casein Increase Body Weight and Whey and Casein Increase the Plasma C-Peptide Concentration in Overweight Adolescents

In adults, dietary protein seems to induce weight loss and dairy proteins may be insulinotropic. However, the effect of milk proteins in adolescents is unclear. The objective was to test whether milk and milk proteins reduce body weight, waist circumference, homeostatic model assessment, plasma insulin, and insulin secretion estimated as the plasma C-peptide concentration in overweight adolescents. Overweight adolescents (n = 203) aged 12-15 y with a BMI of 25.4 ± 2.3 kg/m(2) (mean ± SD) were randomized to 1 L/d of skim milk, whey, casein, or water for 12 wk. All milk drinks contained 35 g protein/L. Before randomization, a subgroup of adolescents (n = 32) was studied for 12 wk before the intervention began as a pretest control group. The effects of the milk-based test drinks were compared with baseline (wk 0), the water group, and the pretest control group. Diet and physical activity were registered. Outcomes were BMI-for-age Z-scores (BAZs), waist circumference, plasma insulin, homeostatic model assessment, and plasma C-peptide. We found no change in BAZ in the pretest control and water groups, whereas it was greater at 12 wk in the skim milk, whey, and casein groups compared with baseline and with the water and pretest control groups. The plasma C-peptide concentration increased from baseline to wk 12 in the whey and casein groups and increments were greater than in the pretest control (P < 0.02). There were no significant changes in plasma C-peptide in the skim milk or water group. These data suggest that high intakes of skim milk, whey, and casein increase BAZs in overweight adolescents and that whey and casein increase insulin secretion. Whether the effect on body weight is primary or secondary to the increased insulin secretion remains to be elucidated.

Central Adiposity and Protein Intake Are Associated with Arterial Stiffness in Overweight Children

Being overweight is associated with vascular abnormalities, which are important in the development of atherosclerosis. However, little is known about dietary and lifestyle determinants of vascular function in overweight children. In adults, dietary protein and milk intake are associated with reduced blood pressure and reduced risk of metabolic syndrome. This study examined the associations between dietary protein, milk intake, physical activity, and adiposity on arterial stiffness in overweight children. In a cross-sectional study, overweight children with habitual milk intakes ≤ 250 mL/d were examined by DXA scans, pedometer counts, anthropometry, and metabolic variables. Dietary intake was registered for 4 d. The outcomes were arterial stiffness measured by pulse wave velocity (PWV) (n = 182) and augmentation index (Aix) (n = 183). The PWV (mean ± SD) was 4.78 ± 0.72 m/s and the Aix was -0.77 ± 9.44%. In multivariate models, the android fat:gynoid fat and android fat:body fat ratios were positively associated with PWV (β = 1.49 and β = 10.3, both P < 0.05) and Aix (β = 28.3, P < 0.01 and β = 153, P < 0.05), whereas the gynoid fat:body fat ratio was negatively associated with the Aix (β = -134; P < 0.001). Protein intake (percentage energy) was positively associated with PWV (β = 0.05; P < 0.01). Milk intake (L/d) tended to be negatively associated with PWV (β = -0.64; P = 0.05). Pedometer counts were negatively associated with the Aix; however, the association became nonsignificant after controlling for HOMA, which was positively associated with the Aix (β = 0.95; P < 0.01). In conclusion, central adiposity and protein intake are associated with increased arterial stiffness measured as PWV in overweight children independent of blood pressure and heart rate. The effect of protein intake may be caused by meat, because the milk intake was low.

Milk and growth in children: effects of whey and casein.

Consumption of cows milk is recommended in many countries. Observational and intervention studies show that cows milk most likely has a positive influence on growth in children. The strongest evidence comes from observational studies and intervention studies in low-income countries, but there are also observational studies from high-income countries showing positive associations between milk intake and growth. Milk seems thus to have a specific stimulating effect on linear growth, not only in developing countries with high rates of malnutrition, but also in industrialized countries. However, it is not known which components in milk stimulate growth. Possible components are proteins, minerals, vitamins or combinations of these. Cows milk proteins have a high protein quality, and whey has a slightly higher quality than casein, according to some indices based on amino acid composition. Studies, mainly from sport medicine, have suggested that whey protein also has the potential to increase muscle mass. Whether whey improves body composition to a larger extent than other milk proteins is not clear. The mechanism behind a possible growth-stimulating effect of milk and milk components is likely to be through a stimulation of insulin-like growth factor-I synthesis and maybe insulin secretion. In conclusion, there is strong evidence that milk stimulates linear growth. The mechanism is not yet clear, and more intervention studies are needed to understand which components in milk are responsible for the growth stimulation. The effects of milk on linear growth and adult height may have both positive and negative long-term implications.

NMR-Based Metabolomic Profiling of Overweight Adolescents: An Elucidation of the Effects of Inter-/Intraindividual Differences, Gender, and Pubertal Development

The plasma and urine metabolome of 192 overweight 12–15-year-old adolescents (BMI of 25.4 ± 2.3 kg/m2) were examined in order to elucidate gender, pubertal development measured as Tanner stage, physical activity measured as number of steps taken daily, and intra-/interindividual differences affecting the metabolome detected by proton NMR spectroscopy. Higher urinary excretion of citrate, creatinine, hippurate, and phenylacetylglutamine and higher plasma level of phosphatidylcholine and unsaturated lipid were found for girls compared with boys. The results suggest that gender differences in the metabolome are being commenced already in childhood. The relationship between Tanner stage and the metabolome showed that pubertal development stage was positively related to urinary creatinine excretion and negatively related to urinary citrate content. No relations between physical activity and the metabolome could be identified. The present study for the first time provides comprehensive information about associations between the metabolome and gender, pubertal development, and physical activity in overweight adolescents, which is an important subject group to approach in the prevention of obesity and life-style related diseases. While this study is preliminary, these results may have the potential to translate into clinical applicability upon further investigations; if biomarkers for Tanner stage can be established, these might be used for identification of individuals susceptible to an early pubertal development.

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.

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.

Effect of milk proteins on linear growth and IGF variables in overweight adolescents.

OBJECTIVE Milk may stimulate growth acting via insulin-like growth factor-I (IGF-I) secretion but the effect in adolescents is less examined. This study investigates the effect of milk proteins on linear growth, IGF-I, IGF binding protein-3 (IGFBP-3) and IGF-I/IGFBP-3 ratio in overweight adolescents. DESIGN The trial included 193 overweight adolescents aged 12-15 years. They were randomized to drink 1L/day of: skimmed milk, whey, casein or water for 12 weeks; all milk-based drinks contained 35 g protein/L. A subgroup of 32 adolescents was examined 12 weeks before they were randomized into the groups and started the intervention (pre-test control group). Examinations included anthropometry, diet registration and blood samples which were analyzed for IGF-I and IGFBP-3 by chemiluminescence methods. The effects of milk-based drinks on linear growth, IGF-I, IGFBP-3 and IGF-I availability, calculated as the IGF-I/IGFBP-3 ratio, were compared with baseline, the pre-test control group and water. RESULTS IGF-I increased with skimmed milk (P=0.015) and tended to increase with casein (P=0.075) compared to the pre-test control group. IGFBP-3 but not IGF-I increased with skimmed milk (P=0.006) and casein (P=0.001) compared to water. There was no difference in height or height Z-score for any of the milk-based test drink groups compared to water or compared to the pre-test control group. However, height Z-score decreased within the whey group. CONCLUSIONS Skimmed milk and casein may have a stimulating effect on the IGF-I system whereas there was no positive effect on height in overweight adolescents during this 12 week intervention.

Casein improves brachial and central aortic diastolic blood pressure in overweight adolescents: a randomised, controlled trial

Arterial stiffness, blood pressure (BP) and blood lipids may be improved by milk in adults and the effects may be mediated via proteins. However, limited is known about the effects of milk proteins on central aortic BP and no studies have examined the effects in children. Therefore, the present trial examined the effect of milk and milk proteins on brachial and central aortic BP, blood lipids, inflammation and arterial stiffness in overweight adolescents. A randomised controlled trial was conducted in 193 overweight adolescents aged 12–15 years. They were randomly assigned to drink 1 litre of water, skimmed milk, whey or casein for 12 weeks. The milk-based test drinks contained 35 g protein/l. The effects were compared with the water group and a pretest control group consisting of thirty-two of the adolescents followed 12 weeks before the start of the intervention. Outcomes were brachial and central aortic BP, pulse wave velocity and augmentation index, serum C-reactive protein and blood lipids. Brachial and central aortic diastolic BP (DBP) decreased by 2·7% (P = 0·036) and 2·6 % (P = 0·048), respectively, within the casein group and the changes were significantly different from those of the pretest control group (P = 0·040 and P = 0·034, respectively). There was a significant increase in central aortic DBP, and in brachial and central systolic BP in the whey group compared with the water group (P = 0·003, P = 0·009 and P = 0·002, respectively). There were no changes in measures of arterial stiffness or blood lipid concentrations. A high intake of casein improves DBP in overweight adolescents. Thus, casein may be beneficial for younger overweight subjects in terms of reducing the long-term risk of CVD. In contrast, whey protein seems to increase BP compared with drinking water; however, water may be considered an active control group.

The effects of water and dairy drinks on dietary patterns in overweight adolescents

Abstract The aim was to investigate the effects of increased water or dairy intake on total intake of energy, nutrients, foods and dietary patterns in overweight adolescents in the Milk Components and Metabolic Syndrome (MoMS) study (n= 173). Participants were randomly assigned to consume 1l/d of skim milk, whey, casein or water for 12 weeks. A decrease in the dietary pattern called Convenience Food, identified by principal component analysis, was observed during the intervention both in the water and dairy groups. Total energy intake decreased by 990.9 kJ/d (236.8 kcal/d) in the water group but was unchanged in the dairy group during intervention. To conclude, an extra intake of fluid seems to favourably affect the rest of the diet by decreasing the intake of convenience foods, including sugar-sweetened beverages. A low energy drink, such as water, seems advantageous considering the total energy intake in these overweight adolescents. This study is registered at clinicaltrials.gov (NCT00785499).

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

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.