Effects of school milk intervention on cortical bone accretion and indicators relevant to bone metabolism in Chinese girls aged 10-12 y in Beijing

Calcium and Iron Nutrition through the Reproductive Life Course

BACKGROUND

Two essential micronutrients over the life course are calcium and iron, and both are especially important during the reproductive cycle. The role of calcium in maternal and offspring bone health and in the prevention of pre-eclampsia in pregnancy are well described, although results from randomised controlled trials for both outcomes vary. Iron is essential for synthesis of red blood cells, being a core component of haemoglobin, which carries oxygen around the body, and hence is key in the prevention of anaemia and sequelae.

SUMMARY

This article reviews the evidence across the reproductive life course for dietary calcium and iron intakes and health outcomes. For calcium, focusing on bone health and prevention of pre-eclampsia, for iron considering its crucial role in foetal and neonatal development and how requirements may be impacted through inflammation and infection, particularly in environments where iron availability may be low.

Dairy Consumption and Its Impact on PCOS and the Reproductive System: The Connection

Polycystic ovary syndrome (PCOS) is a prevalent and complex endocrine disorder that affects many women of reproductive age. It is characterized by hyperandrogenism, ovulatory dysfunction, and polycystic ovarian morphology. PCOS is associated with an increased risk of cardiovascular disease, obesity, diabetes, and other long-term health conditions, including cancer. Given its widespread impact, it should be recognized as a significant public health concern, highlighting the urgent need to investigate its underlying causes and the behavioral factors contributing to its rising prevalence. The increasing prevalence of PCOS is closely linked to the global and national rise in obesity. Alarmingly, a significant portion of cases remain undiagnosed. Although the etiology of PCOS has yet to be elucidated, the general consensus is that obesity and insulin resistance (IR) are likely strong contributing factors. Although the etiology of IR is multifactorial, some believe that it may be associated with dairy consumption. Dairy, particularly cow's milk, has been a staple in the Western diet for decades; however, over the past 50 years, due to the popularization from marketing campaigns promoting it as beneficial for bone health, its consumption has now skyrocketed. There has been a growing focus on the role of dairy products on disease, especially regarding their impact on ovulation, fertility, and endocrinologic/metabolism disorders. Here, we attempt to review the contemporary evidence examining the possible role and relationship of dairy products to the pathophysiology of PCOS. We hope to clarify to the reader, based on the best available evidence, whether a low-dairy diet may help improve PCOS parameters and its comorbid conditions. This review aims to explore this question with the goal of addressing gaps in the current understanding of the interplay between dairy consumption and hormonal/metabolic dysfunction.

Moderate-to-vigorous physical activity modulates the association between serum 25-hydroxyvitamin D and bone stiffness in European children and adolescents

It remains unclear how serum 25-hydroxyvitamin D (25(OH)D) concentrations relate to childhood bone health. We hypothesized that 25(OH)D was inversely associated with bone turnover biomarkers and positively associated with bone stiffness. Cross-sectional analyses were performed using data from participants (2-15-year-old, 51% boys) from the Identification and Prevention of Dietary- and Lifestyle-induced Health Effects in Children and Infants Study (IDEFICS)/I.Family cohort, comprising 3,638 serum 25(OH)D measurements collected in 2007-2008 and 2012-2013 across eight European countries. A biomarker of bone formation (serum osteocalcin), a biomarker of bone resorption (serum C-terminal telopeptides of type I collagen [CTx]), and stiffness index measured using calcaneal quantitative ultrasound were considered outcomes. Linear mixed-effects models were used to adjust for confounders (i.e., age, sex, parental education, time spent in sports club, dairy products consumption, sedentary behavior, height and weight z-scores), the cluster effect of country and repeated measurements. Interactions of calcium intake, moderate-to-vigorous physical activity (MVPA) and weight status with 25(OH)D on outcomes were tested. Only 1 in 3 participants reached the sufficient 25(OH) D concentration of 20 ng/mL. Sufficient 25(OH)D was associated with higher stiffness index if participants had MVPA ≥60 min/day (β = 12.14, P < .05). Moreover, 25(OH)D was inversely associated with CTx (β = -7.09, P < .05); this association was positive but not statistically significant among primary school children living with overweight/obesity. No interaction was observed for calcium intake. In conclusion, serum 25(OH)D and CTx were inversely associated. MVPA interacted with the positive association between 25(OH)D and bone stiffness, highlighting the importance of promoting MVPA guidelines in future vitamin D and bone health interventions.

The Effects of Dairy Product Supplementation on Bone Health Indices in Children Aged 3 to 18 Years: A Meta-Analysis of Randomized Controlled Trials

Childhood and adolescence are critical periods for optimizing skeletal growth. Dairy products are valuable sources of bone-beneficial nutrients, particularly calcium and protein. A random-effects meta-analysis of published randomized controlled trials was performed to quantitatively assess the effects of dairy supplementation on bone health indices in children and adolescents. The PubMed and Web of Science databases were searched. Dairy supplementation increased whole-body bone mineral content (BMC) (+25.37 g) and areal bone mineral density (aBMD) (+0.016 g/cm2), total hip BMC (+0.49 g) and aBMD (+0.013 g/cm2), femoral neck BMC (+0.06 g) and aBMD (+0.030 g/cm2), lumbar spine BMC (+0.85 g) and aBMD (+0.019 g/cm2), and height (0.21 cm). When expressed as a percentage difference, whole-body BMC was increased by 3.0%, total hip BMC by 3.3%, femoral neck BMC by 4.0%, lumbar spine BMC by 4.1%, whole-body aBMD by 1.8%, total hip aBMD by 1.2%, femoral neck aBMD by 1.5%, and lumbar spine aBMD by 2.6%. Dairy supplementation increased serum insulin-like growth factor I concentrations (19.89 nmol/L) and reduced concentrations of urinary deoxypyridinoline (-1.78 nmol/mmol creatinine) and serum parathyroid hormone (-10.46 pg/mL) but did not significantly affect the serum concentrations of osteocalcin, bone alkaline phosphatase, and C-terminal telopeptide of type 1 collagen. Serum 25-hydroxyvitamin D concentrations (+4.98 ng/mL) increased with vitamin D-fortified dairy supplementation. The positive effects on bone mineral mass parameters and height were generally consistent across subgroups defined by sex, geographical region, baseline calcium intake, calcium from the supplementation, trial duration, and Tanner stages. In summary, dairy supplementation during growth leads to a small but significant increase in bone mineral mass parameters, and these findings are generally supported by the changes in several biochemical parameters related to bone health.

Fortification of Staple Foods for Household Use with Vitamin D: An Overview of Systematic Reviews

Vitamin D deficiency is a global public health concern with significant implications for bone health and chronic disease prevention. Our aim was to summarize the evidence from Cochrane and other systematic reviews evaluating the benefits or harms of vitamin D fortification of staple foods for household use. In April 2023, we systematically searched Ovid MEDLINE, Embase, Epistemonikos and the Cochrane Database of Systematic Reviews for systematic reviews investigating the effects of vitamin D fortification of food in general populations of any age. We used Cochrane methodology and assessed the methodological quality of included studies using AMSTAR (A MeaSurement Tool to Assess Systematic Reviews). We assessed the degree of overlap among reviews. All outcomes included in systematic reviews were assessed. The protocol is registered in PROSPERO (registration number: CRD42023420991). We included 27 systematic reviews out of 5028 records for analysis. Overall, 11 out of 12 systematic reviews calculating pooled estimates reported a significant increase in serum 25(OH)D concentrations. The mean change in serum 25(OH)D concentrations per additional 100 units of vitamin D ranged from 0.7 to 10.8 nmol/L. Fortification of food with vitamin D showed a reduction in the prevalence of vitamin D deficiency based on high-certainty evidence. Parathormone (PTH) levels were described to decrease, bone mineral density to increase, while the effects on other bone turnover markers were inconsistent. Fortification did not significantly impact most anthropometric parameters, but it seemed to positively influence lipid profiles. In summary, fortification of food with vitamin D results in a reduction of vitamin D deficiency and might increase serum 25(OH)D concentrations, to varying extents depending on the fortified vehicle and population characteristics. Additionally, fortification may have a positive impact on bone turnover and lipid metabolism but may only have a limited effect on anthropometric parameters.

Formula Milk Supplementation and Bone Acquisition in 4-6 Years Chinese Children: A 12-Month Cluster-Randomized Controlled Trial

Dairy foods are crucial for adequate calcium intake in young children, but scarce data are available on the effects of formula milk on bone acquisition. This cluster-randomized controlled trial investigated the effects of the supplementation of formula milk on bone health in rural children accustomed to a low-calcium diet between September 2021 and September 2022. We recruited 196 healthy children aged 4-6 years from two kindergartens in Huining County, Northwest China. A class-based randomization was used to assign them to receive 60 g of formula milk powder containing 720 mg calcium and 4.5 µg vitamin D or 20-30 g of bread per day for 12 months, respectively. Bone mineral density (BMD) and bone mineral content (BMC) at the left forearm and calcaneus, bone biomarkers, bone-related hormones/growth factors, and body measures were determined at baseline, 6, and 12 months. A total of 174 children completed the trial and were included in the analysis. Compared with the control group, formula milk intervention showed significant extra increments in BMD (3.77% and 6.66%) and BMC (4.55% and 5.76%) at the left forearm at 6th and 12th months post-intervention (all p < 0.001), respectively. Similar trends were observed in BMD (2.83%) and BMC (2.38%) in the left calcaneus at 6 months (p < 0.05). The milk intervention (vs. control) also showed significant changes in the serum concentrations of osteocalcin level (-7.59%, p = 0.012), 25-hydroxy-vitamin-D (+5.54%, p = 0.001), parathyroid hormone concentration (-15.22%, p = 0.003), and insulin-like growth factor 1 (+8.36%, p = 0.014). The percentage increases in height were 0.34%, 0.45%, and 0.42% higher in the milk group than in the control group after 3-, 6-, and 9-month intervention, respectively (p < 0.05). In summary, formula milk supplementation enhances bone acquisition at the left forearm in young Chinese children.

Standard vs. Nutrient-Enriched Cow's Milk and Its Impacts on Child Growth: A Systematic Review and Meta-Analysis

Stunting among children indicates malnutrition or undernutrition, hindering their growth and development. This will have negative effects on the overall health of children. This review investigates the effects of different types of cow's milk and their impacts on children's growth. A web-based search of Cochrane, Web of Science, SAGE, and Prospero was carried out using predetermined search/MESH phrases and keywords. The data extraction and analysis were carried out independently by two reviewers, who then double-checked, revised, and discussed any disagreements with a third reviewer. Eight studies met the inclusion criteria and were rated as good (N = 5) and fair quality (N = 3), which were included in the final analysis. The results illustrated that standard cow's milk has more consistent findings than nutrient-enriched cow's milk potentially in assisting children's growth. However, studies on standard cow's milk and child's growth are still lacking for this age group. In addition, there are inconsistent findings between nutrient-enriched cow's milk and children's growth. It is crucial to ensure milk is included in children's diets as per recommended nutrient intake.

Vitamin D biomarkers for Dietary Reference Intake development in children: a systematic review and meta-analysis

BACKGROUND

Circulating 25-hydroxyvitamin D [25(OH)D] has been the accepted vitamin D exposure/intake biomarker of choice within recent DRI exercises, but use of other vitamin D-related biomarkers as well as functional markers has been suggested. These may be of value in future vitamin D DRI exercises, such as the FAO/WHO's one for young children.

OBJECTIVES

To systematically review the usefulness of circulating 25(OH)D, parathyroid hormone (PTH), free and bioavailable 25(OH)D, C3-epimer of 25(OH)D, vitamin D3, 24,25-dihydroxyvitamin D [24,25(OH)2D], and bone turnover markers and calcium absorption as vitamin D biomarkers for DRI development in children.

METHODS

Methods included structured searches of published articles, full-text reviews, data extraction, quality assessment, meta-analysis, and random-effects meta-regression.

RESULTS

Fifty-nine vitamin D supplementation randomized controlled trials (RCTs) were included (39 in infants/children as the priority group and the remainder in adults since pediatric studies were absent/limited). Vitamin D supplementation significantly raised circulating 25(OH)D in infants and children, but the response was highly heterogeneous [weighted mean difference (WMD): 27.7 nmol/L; 95% CI: 22.9, 32.5; 27 RCTs; I2 = 93%]. Meta-regression suggested an increase by 1.7 nmol/L (95% CI: 0.7, 2.6) in serum 25(OH)D per each 100-IU increment in vitamin D intake (P = 0.0005). Vitamin D supplementation had a significant effect on circulating 24,25(OH)2D (WMD: 3.4 nmol/L; 95% CI: 2.4, 4.5; 13 RCTs; I2 = 95%), with a dose-response relation (+0.15 nmol/L per 100 IU; 95% CI: -0.01, 0.29). With circulating PTH, although there was a significant effect of vitamin D on WMD (P = 0.05), there was no significant dose-response relation (P = 0.32). Pediatric data were too limited in relation to the usefulness of the other biomarkers.

CONCLUSIONS

Circulating 25(OH)D may be a useful biomarker of vitamin D exposure/intake for DRI development in infants and children. Circulating 24,25(OH)2D also showed some promise, but further data are needed, especially in infants and children.

Dairy products and bone health

Bone mineral mass, geometry and microstructure, hence determinants of fracture risk, result bone accrual during growth and bone loss later in life. Peak bone mass, which is reached by the end of the second decade of life, is mainly determined by genetic factors. Among other factors influencing bone capital, dietary intakes, particularly calcium and protein, play a significant role in peak bone mass attainment. Both nutrients are provided in dairy products, which accounts for 50-60% and 20-30% of the daily calcium and protein intakes, respectively. Children avoiding dairy products are at higher risk of fracture, as are adults or older individuals following a diet devoid of dairy products, like vegans. Various intervention trials have shown some beneficial effects of dairy products on bone capital accumulation during growth and on bone turnover in adults. In observational studies, dairy products intake, particularly the fermented ones, which also provide probiotics in addition to calcium, phosphorus and protein, appear to be associated with a lower risk of hip fracture.

Impacts of school feeding on educational and health outcomes of school-age children and adolescents in low- and middle-income countries: A systematic review and meta-analysis

Background

School feeding programs are ubiquitous in low- and middle-income countries (LMICs) and may have critical implications for the health and education of school-age children and adolescents. This systematic review aimed to assess the impacts of school feeding on educational and health outcomes of children and adolescents in LMICs.

Methods

Interventional studies on the effects of school feeding on nutritional and health outcomes of children and adolescents receiving primary or secondary education in LMICs were included. MEDLINE, EMBASE, CINAHL, the Cochrane Library, and grey literature were searched (through December 2019) to identify eligible studies. We included randomized controlled trials and controlled before-after studies on school feeding conducted in LMICs among children and adolescents aged 6 to 19 who received primary or secondary education. Two reviewers independently conducted study selection, data extraction, and risk of bias assessment. Meta-analyses were performed for outcomes available in three or more independent studies. Subgroup analyses were conducted by study design and school feeding modality whenever possible.

Results

Fifty-seven articles met the inclusion criteria for the review, including 44 randomized controlled trials and 13 controlled before-after studies; 19 articles were included in the meta-analysis. School feeding resulted in a significant increase in height (mean difference = 0.32 cm; confidence interval (CI) = 0.03, 0.61; P = 0.032) and weight (mean difference: 0.58 kg; 95% 95% CI = 0.22, 0.93; P = 0.001) over 12 months, compared to those in the control groups. School feeding also resulted in a significant increase in the percentage of school days attended (2.6%; 95% CI = 1.2%, 3.9%; P < 0.001).

Conclusions

School feeding is an important approach to improving the health and education outcomes of children and adolescents living in LMICs. More well-designed research is needed to establish further the effectiveness of school feeding for nutritional outcomes and academic achievement.

Registration

PROSPERO ID: CRD42020159003.

School-based nutrition interventions can improve bone health in children and adolescents

Objectives

Osteoporosis is a major global health problem, and optimizing bone health during childhood and adolescence with adequate calcium and vitamin D intake is a recommendation to prevent the disease. School milk programs may be a viable approach to help children and adolescents increase calcium and vitamin D intakes while improving their bone health.

Methods

A review of the literature was conducted on school milk programs, including examination of details regarding these studies and their participants, and assessments of their effects on bone health in children and adolescents.

Results

Nearly all studies reviewed showed significant increases in the bone health behaviors and outcomes that were measured, such as bone mineral density, milk consumption, and calcium and vitamin D intake.

Conclusions

School milk programs can be effective in improving bone health in children and adolescents, and public health policies should be considered to help support and fund effective programs that promote bone health and prevent osteoporosis in population health.

Effects of preventive nutrition interventions among adolescents on health and nutritional status in low- and middle-income countries: A systematic review

Background

Malnutrition is one of the most common causes of morbidity and mortality among children and adolescents and is now considered to be one of the largest risk factors responsible for the global burden of diseases along with poor diet.

Objectives

The objective of this review was to assess the impact of preventive nutrition interventions (including nutrition education and counselling; micronutrient supplementation/fortification and macronutrient supplementation) to improve the health and nutritional status of adolescents aged 10-19 years in low- and middle-income countries (LMICs). The secondary objective of the review was to assess various contextual factors based on the World Health Organisation (WHO) health system building blocks framework that might potentially impact the effectiveness of these interventions for this age group.

Search Methods

The search was conducted on Cochrane Controlled Trials Register (CENTRAL), MEDLINE, EMBASE, CINAHL, PsycINFO, the WHO nutrition databases, CAB Global Health, Social Science Citation Index, Scopus, WHO Global Health Index, ADOLEC and EPPI until February 5, 2019. We searched Google Scholar along with key nutrition agencies database such as Nutrition International, the Global Alliance for Improved Nutrition, the World Food Programme and HarvestPlus to search for nonindexed, grey literature to locate relevant programme evaluations and any additional trials. All searches were performed without any restrictions on publication date, language or publication status.

Selection Criteria

We included randomised controlled trials, quasiexperimental studies, controlled before-after studies and interrupted time series evaluating the effectiveness of preventive nutrition interventions among adolescents between 10 and 19 years of age from LMICs.

Data Collection and Analysis

Two review authors independently assessed trials for inclusion, assessed risk of bias and extracted data from included studies. Meta-analysis was conducted separately for each outcome and intervention. For dichotomous data, we reported risk ratios (RR) with 95% confidence intervals (CI). For continuous data, we reported the mean difference (MD) or standard mean difference (SMD) with 95% CI.

Main Results

This review summarises findings from a total of 10 studies from 15 papers including 10,802 participants. All the studies included in this review assessed the impact of micronutrient supplementation/fortification on health and nutritional status among adolescents in LMIC. We did not find any study assessing the impact of nutrition education and counselling or on macronutrient supplementation among adolescents. Micronutrient supplementation/fortification interventions included calcium/vitamin D supplementation/fortification, iron supplementation with or without folic acid, zinc supplementation and multiple micronutrient (MMN) fortification. The majority of the studies (eight out of 10 studies) included adolescent girls aged between 10 and 19 years of age. We did not find any large scale preventive nutrition intervention programmes targeting adolescents in LMICs. We are uncertain of the effect of iron supplementation with or without folic acid on anaemia (daily supplementation; RR: 1.04, 95% CI 0.88, 1.24; one study; 1,160 participants; low quality evidence. Weekly supplementation; RR: 1.07, 95% CI: 0.91, 1.26; one study; 1,247 participants; low quality evidence). We are uncertain of the effect of various micronutrient supplementation/fortification on body mass index (calcium/vitamin D supplementation; (MD: -0.01 kg/m2; 95% CI: -1.20, 1.17; two studies; 730 participants; I 2 94%; very low quality evidence, iron supplementation with or without folic acid; MD: 0.29 kg/m2; 95% CI: -0.25, 0.83; two studies; 652 participants; I 2 69%; very low quality evidence, zinc supplementation; MD: 0.35 kg/m2; 95% CI: -0.15, 0.85; one study; 382 participants; very low quality evidence) and MMN fortification; MD: 0.23 kg/m2, 95% CI: -0.11, 0.57; two studies; 943 participants; I 2 22%; very low quality evidence). None of the included studies reported any other primary outcomes including morbidity or adverse effects. Iron supplementation with or without folic acid may improve haemoglobin concentrations (MD: 0.42 g/dL, 95% CI: 0.13, 0.71; four studies; 1,020 participants; I 2 89%; low quality evidence). Calcium/vitamin D supplementation may improve serum 25(OH) D levels (standardised mean difference [SMD]: 2.85, 95% CI: 0.89, 4.82; two studies; 395 participants; I 2 99%; low quality evidence). We are uncertain of the effect of calcium only supplementation (MD: 0.02 g/cm2, 95% CI: -0.00, 0.04; one study; 233 participants; low quality outcome) and calcium + vitamin D supplementation (MD: 0.02 g/cm2, 95% CI: -0.00, 0.04; one study; 235 participants; low quality evidence) on total bone mineral density (BMD). We are uncertain of the effect of MMN fortification on haemoglobin concentrations (MD: -0.10 g/dL, 95% CI: -0.88, 0.68; two studies; 1102 participants; I 2 100%; very low quality evidence); calcium supplementation on total body bone mineral content (BMC); (MD: 30.20 g, 95% CI: -40.56, 100.96; one study; 233 participants; low quality evidence), calcium + vitamin D supplementation on total body BMC (MD: 21.60 g, 95% CI: -45.32, 88.52; one study; 235 participants; low quality evidence) and zinc supplementation on serum zinc levels (SMD: 6.94, 95% CI: -4.84, 18.71; two studies; 494 participants; very low quality evidence). One study reported the impact of iron supplementation with or without folic acid on cognition of adolescent girls suggesting improved cognition in most of the tests with daily or twice weekly supplementation compared to once weekly or no supplementation. None of the other secondary outcomes were reported including any other development outcomes and all-cause mortality. These findings warrant caution while interpreting due to very few studies and high heterogeneity.

Authors' Conclusions

There is limited evidence of micronutrient supplementation/fortification among adolescents on health and nutritional status in LMICs, with lack of evidence on nutrition education and counselling and macronutrient supplementation. The findings are generaliseable for adolescent girls since all studies (except one) targeted female adolescents.

Effects of Preventive Nutrition Interventions among Adolescents on Health and Nutritional Status in Low- and Middle-Income Countries: A Systematic Review and Meta-Analysis

The objective of this review was to assess the impact of preventive nutrition interventions on health and nutritional status of adolescents aged 10–19 years in low- and middle-income countries (LMICs). We searched the databases until 5 February 2019 without any restrictions on publication, date, language, or publication status. A total of 10 studies (15 papers) including 10,802 participants assessing the impact of micronutrient supplementation/fortification were included in this review. We did not find any study assessing the impact of nutrition education and counseling or macronutrient supplementation among adolescents. Among primary outcomes, we are uncertain of the effect of iron supplementation with or without folic acid on anemia (daily supplementation; relative risk (RR): 1.04, 95% confidence interval (CI) 0.42, 2.57; one study; 1160 participants; low-quality evidence; weekly supplementation; RR: 1.07, 95% CI: 0.46, 2.52; one study; 1247 participants; low-quality evidence). We are also uncertain of the effect of various micronutrient supplementation/fortification on body mass index (BMI) (calcium/vitamin D supplementation; (MD: −0.01 kg/m²; 95% CI: −1.20, 1.17; two studies; 730 participants; I² 94%; very-low-quality evidence, iron supplementation with or without folic acid; MD: 0.47 kg/m²; 95% CI: −0.17, 1.11; two studies; 652 participants; I² 37%; very-low-quality evidence, zinc supplementation; MD: 0.35 kg/m²; 95% CI: −0.15, 0.85; one study; 382 participants; very-low-quality evidence) and multiple micronutrient (MMN) fortification; MD: 0.23 kg/m², 95% CI: −0.11, 0.57; two studies; 943 participants; I² 22%; very-low-quality evidence). None of the included studies reported any other primary outcomes including morbidity or adverse effects. Among secondary outcomes, iron supplementation with or without folic acid may improve hemoglobin concentrations, and calcium/vitamin D supplementation may improve serum 25(OH)D levels, while calcium only supplementation and calcium and vitamin D supplementation may marginally improve total body bone mineral density (BMD). We are uncertain of the effect of MMN fortification on hemoglobin concentrations, calcium supplementation on total body bone mineral content (BMC), calcium + vitamin D supplementation on total body BMC, and zinc supplementation on zinc levels. There is limited evidence of micronutrient supplementation/fortification among adolescents, especially adolescent boys, on health and nutritional status in LMICs. These findings should be interpreted with caution due to the low quality and limited number of studies.

Increased protein intake affects pro-opiomelanocortin (POMC) processing, immune function and IGF signaling in peripheral blood mononuclear cells of home-dwelling old subjects using a genome-wide gene expression approach

Background

Adequate protein intake among older adults is associated with better health outcomes such as immune function and metabolic regulation of skeletal muscle, but conflicting results make it difficult to define the optimal intake. To further understand the impact of protein intake on metabolic processes, the aim of the study was to explore genome-wide gene expression changes in peripheral blood mononuclear cells (PBMCs) in home-dwelling old subjects after increased protein intake for 12 weeks.

Method

In a parallel double-blind randomized controlled intervention study, subjects (≥ 70 years) received a protein-enriched milk (2 × 20 g protein/day, n = 14, mean (±SD) age 76.9 ± 4.9 years) or an isocaloric carbohydrate drink (n = 17, mean (±SD) age 77.7 ± 4.8 years) for breakfast and evening meal for 12 weeks. PBMCs were isolated before and after the intervention. Microarray analysis was performed using Illumina technology. Serum levels of gut peptides and insulin growth factor (IGF)-1 were also measured.

Results

In total 758 gene transcripts were regulated after increased protein intake, and 649 gene transcripts were regulated after intake of carbohydrates (p < 0.05). Forty-two of these genes were overlapping. After adjusting for multiple testing, 27 of the 758 gene transcripts were regulated (FDR, q-value < 0.25) after protein intake. Of these 25 were upregulated and two downregulated. In particular, genes and signaling pathways involved in pro-opiomelanocortin (POMC) processing, immune function, and IGF signaling were significantly altered.

Conclusions

PBMCs can be used to study gene expression changes after long-term protein intake, as many signaling pathways were regulated after increased protein intake. The functional significance of these findings needs to be further investigated.

Trial registration

ClinicalTrials.gov, ID no. NCT02218333. The study was registered on August 18, 2014.

Whey protein in cancer therapy: A narrative review

Cancer remains a public health challenge in the identification and development of ideal pharmacological therapies and dietary strategies. The use of whey protein as a dietary strategy is widespread in the field of oncology. The two types of whey protein, sweet or acid, result from several processing techniques and possess distinct protein subfraction compositions. Mechanistically, whey protein subfractions have specific anti-cancer effects. Alpha-lactalbumin, human α-lactalbumin made lethal to tumor cell, bovine α-lactalbumin made lethal to tumor cell, bovine serum albumin, and lactoferrin are whey protein subfractions with potential to hinder tumor pathways. Such effects, however, are principally supported by studies performed in vitro and/or in vivo. In clinical practice, whey protein intake-induced anti-cancer effects are indiscernible. However, whey protein supplementation represents a practical, feasible, and cost-effective approach to mitigate cancer cachexia syndrome. The usefulness of whey protein is evidenced by a greater leucine content and the potential to modulate IGF-1 concentrations, representing important factors towards musculoskeletal hypertrophy. Further clinical trials are warranted and needed to establish the effects of whey protein supplementation as an adjuvant to cancer therapy.

25-Hydroxyvitamin D as a Biomarker of Vitamin D Status and Its Modeling to Inform Strategies for Prevention of Vitamin D Deficiency within the Population

There is substantial evidence that the prevalence of vitamin D deficiency is unacceptably high in the population, and this requires action from a public health perspective. Circulating 25-hydroxyvitamin D [25(OH)D] is a robust and reliable marker of vitamin D status and has been used by numerous agencies in the establishment of vitamin D dietary requirements and for population surveillance of vitamin D deficiency or inadequacy. In a wider context, modeling of serum 25(OH)D data and its contributory sources, namely dietary vitamin D supply and UVB availability, can inform our understanding of population vitamin D status. The aim of this review is to provide the current status of knowledge in relation to modeling of such vitamin D-relevant data. We begin by highlighting the importance of the measurement of 25(OH)D and its standardization, both of which have led to new key data on the prevalence of vitamin D deficiency and inadequacy in North America and Europe. We then overview how state-of-the-art modeling can be used to inform our understanding of the potential effect of ergocalciferol and 25(OH)D on vitamin D intake estimates and how meteorological data on UVB availability, when coupled with other key data, can help predict population serum 25(OH)D concentration, even accounting for seasonal fluctuations, and lastly, how these in silico approaches can help inform policymakers on strategic options on addressing low vitamin D status through food-based approaches and supplementation. The potential of exemplar food-based solutions will be highlighted, as will the possibility of synergies between vitamin D and other dairy food-based micronutrients, in relation to vitamin D status and bone health. Lastly, we will briefly consider the interactions between season and vitamin D supplements on vitamin D status and health.

Functional analysis of the IGF-system in milk

The development of milk during evolution is considered a more recent step to provide the neonate with adequate amounts of energy, nutrients, and specific hormonal signals thereby, granting a fast and efficient rate of postnatal growth and development. Since the insulin- or the insulin-like growth factor (IGF) systems were evolved much earlier, it can be assumed that the functionality of the IGF-system has been integrated into the novel matrix milk containing casein and whey proteins from the beginnings. In fact, IGFs and IGF-binding proteins (IGFBPs) are abundantly present in milk, which is particularly true for fore-milk or colostrum and the potential effects of milk-borne IGF-compounds on the consuming organisms have in fact been addressed by several studies. Those studies examined, if orally administered IGFs can be absorbed by the consumer's gastro-intestinal tract and thus contribute e.g. to the somatic growth of infants. A second line of studies assessed local effects of milk-borne IGFs on growth and development of the gastro-intestinal tract itself. Finally, distinct functions of isolated IGF-compounds for growth and involution of the mammary gland have also been provided in the past. While the consumption of milk seems not to represent a major source of endogenous IGFs, accumulating evidence indicates secondary effects of milk on the endogenous IGF-system, which may be mediated by micronutrients such as branched amino acids and metabolic programming. By contrast, direct effects on growth and development of oesophageal and intestinal cells have been observed if IGFs were administered orally.

Does milk intake promote prostate cancer initiation or progression via effects on insulin-like growth factors (IGFs)? A systematic review and meta-analysis

PURPOSE

To establish whether the association between milk intake and prostate cancer operates via the insulin-like growth factor (IGF) pathway (including IGF-I, IGF-II, IGFBP-1, IGFBP-2, and IGFBP-3).

METHODS

Systematic review, collating data from all relevant studies examining associations of milk with IGF, and those examining associations of IGF with prostate cancer risk and progression. Data were extracted from experimental and observational studies conducted in either humans or animals, and analyzed using meta-analysis where possible, with summary data presented otherwise.

RESULTS

One hundred and seventy-two studies met the inclusion criteria: 31 examining the milk-IGF relationship; 132 examining the IGF-prostate cancer relationship in humans; and 10 animal studies examining the IGF-prostate cancer relationship. There was moderate evidence that circulating IGF-I and IGFBP-3 increase with milk (and dairy protein) intake (an estimated standardized effect size of 0.10 SD increase in IGF-I and 0.05 SD in IGFBP-3 per 1 SD increase in milk intake). There was moderate evidence that prostate cancer risk increased with IGF-I (Random effects meta-analysis OR per SD increase in IGF-I 1.09; 95% CI 1.03, 1.16; n = 51 studies) and decreased with IGFBP-3 (OR 0.90; 0.83, 0.98; n = 39 studies), but not with other growth factors. The IGFBP-3 -202A/C single nucleotide polymorphism was positively associated with prostate cancer (pooled OR for A/C vs. AA = 1.22; 95% CI 0.84, 1.79; OR for C/C vs. AA = 1.51; 1.03, 2.21, n = 8 studies). No strong associations were observed for IGF-II, IGFBP-1 or IGFBP-2 with either milk intake or prostate cancer risk. There was little consistency within the data extracted from the small number of animal studies. There was additional evidence to suggest that the suppression of IGF-II can reduce tumor size, and contradictory evidence with regards to the effect of IGFBP-3 suppression on tumor progression.

CONCLUSION

IGF-I is a potential mechanism underlying the observed associations between milk intake and prostate cancer risk.

Calcium revisited, part III: effect of dietary calcium on BMD and fracture risk

Food can be an excellent source of calcium. Dietary calcium is in general as well absorbed as calcium supplements, and exerts the same effects on bone. The main sources are dairy products, but also some vegetables and fruits contain considerable amounts of calcium. Mineral water can serve as a supplement. Cross-sectional, longitudinal and some interventional trials have shown positive effects on bone metabolism, bone density and bone loss. But the effect on fracture incidence is less certain, and that of milk, the most studied dairy product, still unproven.

Conflicting reports on vitamin D supplementation: Evidence from randomized controlled trials

A significant number of children and adolescents worldwide have low serum 25(OH)D values relative to the 2010 Institute of Medicine criteria. Since approximately 90% of adult bone mineral content (BMC) is accrued by the end of adolescence, and approximately 40% of adult BMC accumulated during the 4 years surrounding peak BMC velocity, low circulating 25(OH)D during this time may attenuate gains in adolescent bone strength. Reduced bone mineralization and strength during pubertal growth tracks into adulthood and could lead to an increased risk of skeletal fractures. Observational studies examining the relationships between vitamin D and bone are conflicting and few randomized controlled trials (RCTs) have been conducted in children and adolescents. Four of these RCTs, however, provide moderate support for the role of vitamin D supplementation on BMC accrual in adolescent females with baseline serum concentrations <50 nmol/L. Though the daily vitamin D doses employed in these trials ranged from 200 to 3000 IU per day, it is not clear if a dose-response effect exists. Specific maturational stages were associated with optimal bone responses in each of these trials, but they were not consistent across studies. Furthermore, data on male children and among ethnicities other than white and Asian youth were limited in these studies and therefore reduce the generalizability of the findings. Finally, the evidence linking vitamin D supplementation to improved muscle gains and function, important variables to consider in bone health investigations during growth, might imply indirect effects of supplementation on bone. In conclusion, future RCTs are warranted that address the mechanisms by which vitamin D improves bone mineralization in adolescents, including trials that address the impact of vitamin D on muscle function.

Nutritional aspects of bone health

Bone mass, geometry and microstructure, and bony tissue material level properties determine bone strength, hence the resistance to fracture. At a given age, all these variables are the consequence of the amount accumulated and of the structure developed during growth, up to the so-called peak bone mass, and of the bone loss and microstructure degradation occurring later in life. Genetic factors primarily contribute to the variance of the determinants of bone strength. Nutritional intakes are environmental factors that influence both processes, either directly by modifying modelling and remodelling, or indirectly through changes in calcitropic hormone secretion and action. Some effects of nutrition on the offspring bone could take place during foetal life. There are interplays between genetic factors, nutritional intakes and physical exercise. Among the nutrients, sufficient dietary intakes of calcium and protein are necessary for bone health in childhood and adolescence as well as later in life.

The effect of prepubertal calcium carbonate supplementation on skeletal development in Gambian boys-a 12-year follow-up study

CONTEXT

Calcium intake during growth is essential for future bone health but varies widely between individuals and populations. The impact on bone of increasing calcium intake is unknown in a population where low calcium intake, stunting, and delayed puberty are common.

OBJECTIVE

To determine the effect of prepubertal calcium supplementation on mean age at peak velocity for bone growth and mineral accrual.

DESIGN AND SETTING

Prospective follow-up of boys in rural Gambia, West Africa, who had participated in a double-blind, randomized, placebo-controlled trial of calcium supplementation.

PARTICIPANTS

Eighty boys, initially aged 8.0-11.9 years, were followed up for 12 years.

INTERVENTIONS

Subjects received 1 year of calcium carbonate supplementation (1000 mg daily, 5 d/wk).

MAIN OUTCOME MEASURES

Dual-energy x-ray absorptiometry measurements were carried out for whole body (WB), lumbar spine, and total hip bone mineral content, bone area (BA), and WB lean mass. Super imposition by translation and rotation models was made to assess bone growth.

RESULTS

Age at peak velocity was consistently earlier in the calcium group compared to the placebo group, for WB bone mineral content (mean, -6.2 [SE, 3.1]; P = .05), WB BA (mean, -7.0 [SE, 3.2] mo; P = .03), lumbar spine and total hip BA. By young adulthood, supplementation did not change the amount of bone accrued (mineral or size) or the rate of bone growth.

CONCLUSIONS

Twelve months of prepubertal calcium carbonate supplementation in boys with a low calcium diet advanced the adolescent growth spurt but had no lasting effect on bone mineral or bone size. There is a need for caution when applying international recommendations to different populations.

Dairy food intake, peripheral bone structure, and muscle mass in elderly ambulatory women

Previous studies suggest that dairy intake may be associated with reduced bone and muscle loss with aging, but there are limited data in the very old. We evaluated the association between intake of dairy foods and peripheral bone structure and muscle mass in 564 elderly women aged 80 to 92 (mean 84.7) years, who were participants of the Calcium Intake Fracture Outcome Study/CAIFOS Aged Extension Study (CAIFOS/CARES) cohort and attended the 10-year follow-up. Assessments included dairy consumption (milk, yogurt, and cheese) by a validated food frequency questionnaire, 15% tibia bone mass, area and volumetric bone mineral density (vBMD) by peripheral quantitative computed tomography (pQCT), and appendicular bone and skeletal muscle mass by dual-energy X-ray absorptiometry (DXA). Women were categorized according to tertiles of dairy intake: first tertile (≤ 1.5 servings/d), second tertile (1.5 to 2.2 servings/d) and third tertile (≥ 2.2 servings/d). Controlling for confounding factors, pQCT assessment at the 15% tibia showed that compared with those in the first tertile of dairy intake, women in the third tertile had 5.7% greater total bone mass (p = 0.005), principally because of an increase in cortical and subcortical bone mass (5.9%, p = 0.050), resulting in a 6.2% increase in total vBMD (p = 0.013). Trabecular but not cortical and subcortical vBMD was also higher (7.8%, p = 0.044). DXA assessment showed that women in the third tertile of dairy intake had greater appendicular bone mass (7.1%, p = 0.007) and skeletal muscle mass (3.3%, p = 0.014) compared with tertile 1. The associations with bone measures were dependent on dairy protein and calcium intakes, whereas the association with appendicular muscle mass was not totally dependent on dairy protein intake. Our results suggest a positive association of dairy intake with appendicular bone mineralization and muscle mass in elderly women. Because many fractures in this age group are of the appendicular skeleton often associated with falls, dairy intake may be a modifiable lifestyle factor contributing to healthy aging.

Dairy products, yogurts, and bone health

Fracture risk is determined by bone mass, geometry, and microstructure, which result from peak bone mass (the amount attained at the end of pubertal growth) and from the amount of bone lost subsequently. Nutritional intakes are an important environmental factor that influence both bone mass accumulation during childhood and adolescence and bone loss that occurs in later life. Bone growth is influenced by dietary intake, particularly of calcium and protein. Adequate dietary calcium and protein are essential to achieve optimal peak bone mass during skeletal growth and to prevent bone loss in the elderly. Dairy products are rich in nutrients that are essential for good bone health, including calcium, protein, vitamin D, potassium, phosphorus, and other micronutrients and macronutrients. Studies supporting the beneficial effects of milk or dairy products on bone health show a significant inverse association between dairy food intake and bone turnover markers and a positive association with bone mineral content. Fortified dairy products induce more favorable changes in biochemical indexes of bone metabolism than does calcium supplementation alone. The associations between the consumption of dairy products and the risk of hip fracture are less well established, although yogurt intake shows a weakly positive protective trend for hip fracture. By consuming 3 servings of dairy products per day, the recommended daily intakes of nutrients essential for good bone health may be readily achieved. Dairy products could therefore improve bone health and reduce the risk of fractures in later life.

Micronutrient fortification of food and its impact on woman and child health: a systematic review

BACKGROUND

Vitamins and minerals are essential for growth and metabolism. The World Health Organization estimates that more than 2 billion people are deficient in key vitamins and minerals. Groups most vulnerable to these micronutrient deficiencies are pregnant and lactating women and young children, given their increased demands. Food fortification is one of the strategies that has been used safely and effectively to prevent vitamin and mineral deficiencies.

METHODS

A comprehensive search was done to identify all available evidence for the impact of fortification interventions. Studies were included if food was fortified with a single, dual or multiple micronutrients and impact of fortification was analyzed on the health outcomes and relevant biochemical indicators of women and children. We performed a meta-analysis of outcomes using Review Manager Software version 5.1.

RESULTS

Our systematic review identified 201 studies that we reviewed for outcomes of relevance. Fortification for children showed significant impacts on increasing serum micronutrient concentrations. Hematologic markers also improved, including hemoglobin concentrations, which showed a significant rise when food was fortified with vitamin A, iron and multiple micronutrients. Fortification with zinc had no significant adverse impact on hemoglobin levels. Multiple micronutrient fortification showed non-significant impacts on height for age, weight for age and weight for height Z-scores, although they showed positive trends. The results for fortification in women showed that calcium and vitamin D fortification had significant impacts in the post-menopausal age group. Iron fortification led to a significant increase in serum ferritin and hemoglobin levels in women of reproductive age and pregnant women. Folate fortification significantly reduced the incidence of congenital abnormalities like neural tube defects without increasing the incidence of twinning. The number of studies pooled for zinc and multiple micronutrients for women were few, though the evidence suggested benefit. There was a dearth of evidence for the impact of fortification strategies on morbidity and mortality outcomes in women and children.

CONCLUSION

Fortification is potentially an effective strategy but evidence from the developing world is scarce. Programs need to assess the direct impact of fortification on morbidity and mortality.

Animal protein intakes during early life and adolescence differ in their relation to the growth hormone-insulin-like-growth-factor axis in young adulthood

Recent studies provide evidence that insulin-like-growth-factor I (IGF-I) and its binding proteins (IGFBP) IGFBP-2 and IGFBP-3 are related to the risk of several common cancers. It remains to be clarified whether their concentrations can be programmed by protein intake from different sources during growth. This study addressed the hypothesis that animal protein intakes during infancy, mid-childhood, and adolescence differ in their relevance for the growth-hormone (GH)-IGF-I axis in young adulthood. Data from the Dortmund Nutritional and Anthropometric Longitudinally Designed Study participants with at least 2 plausible 3-d weighed dietary records during adolescence (age: girls, 9-14 y; boys, 10-15 y; n = 213), around the adiposity rebound (age 4-6 y; n = 179) or early life (age 0.5-2 y; n = 130), and one blood sample in young adulthood were included in the study. Mean serum concentrations of IGF-I, IGFBP-1, IGFBP-2, and IGFBP-3 were compared between tertiles of habitual animal protein intake using multivariable regression analysis. Habitually higher animal protein intakes in females during puberty were related to higher IGF-I (P-trend = 0.005) and IGFBP-3 (P-trend = 0.01) and lower IGFBP-2 (P-trend = 0.04), but not to IGFBP-1 in young adulthood. In turn, IGF-I concentrations in young adulthood were inversely related to animal protein intakes in early life among males only (P-trend = 0.03), but not to animal protein intake around adiposity rebound (P-trend > 0.5). Our data suggest that, among females, a habitually higher animal protein intake during puberty may precipitate an upregulation of the GH-IGF-I axis, which is still discernible in young adulthood. By contrast, among males, higher animal protein intakes in early life may exert a long-term programming of the GH-IGF-I axis.

Validation of a food-frequency questionnaire for the assessment of calcium intake in schoolchildren aged 9-10 years

Bone mass increases steadily until age 20-30 years, when peak bone mass (PBM) is acquired. Nutrition plays a critical role in achievement of the optimal genetically programmed PBM, with reduction in the risk of osteoporosis later in life. Intake of nutrients can be estimated through the use of various tools; typically, food-frequency questionnaires (FFQs) are used in epidemiologic studies. The aim of this study was to validate a 21-item, semiquantitative FFQ to assess important nutrient intakes for bone health in Italian schoolchildren 9-10 years of age. Relative validation was accomplished through comparison of the 7-days weighed food record (7D records) with an FFQ developed ad hoc, completed by a group of 75 Italian schoolchildren (36 females, 39 males). Agreement between the two methods was evaluated by Spearman's correlation test and Bland-Altman analysis applied on the data on intake of energy, macronutrients, and micronutrients. Particular attention was devoted to nutrients relevant for bone health. Good correlations between the two methods (FFQ and 7D records) were observed for all nutrients. In particular, mean dietary calcium intakes were 725.6 mg/day (95 % CI 683.2-768.1) from 7D records and 892.4 mg/day (95 % CI 844.6-940.2) from the FFQ. These results indicate that our FFQ for schoolchildren aged 9-10 years is highly acceptable as it is an accurate method that can be used in large-scale or epidemiological studies for the evaluation of nutrient intakes important for the prevention of osteoporosis in a similar population.

Does milk and dairy consumption during pregnancy influence fetal growth and infant birthweight? A systematic literature review

It is increasingly acknowledged that the maternal diet influences fetal development and health of the child. Milk and milk products contribute essential nutrients and bioactive substances; they are of ample supply and have a long tradition in Nordic countries. To revise and update dietary guidelines for pregnant women valid in Nordic countries, the Pregnancy and Lactation expert group within the NNR5 project identified a need to systematically review recent scientific data on infant growth measures and maternal milk consumption. The objective of this study was to assess the influence of milk and dairy consumption during pregnancy on fetal growth through a systematic review of studies published between January 2000 and December 2011. A literature search was run in June 2011. Two authors independently selected studies for inclusion from the 495 abstracts according to predefined eligibility criteria. A complementary search in January 2012 revealed 64 additional abstracts published during the period June to December 2011, among them one study of interest previously identified. Of the 33 studies extracted, eight were relevant research papers. Five were prospective cohort studies (including a retrospective chart review), one was a case–control study, and two were retrospective cohort studies. For fetal length or infant birth length, three studies reported no association and two reported positive associations with milk or dairy consumption. For birthweight related outcomes, two studies reported no associations, and four studies reported positive associations with milk and/or dairy consumption. There was large heterogeneity in exposure range and effect size between studies. A beneficial fetal growth-increase was most pronounced for increasing maternal milk intake in the lower end of the consumption range. Evidence from prospective cohort studies is limited but suggestive that moderate milk consumption relative to none or very low intake, is positively associated with fetal growth and infant birthweight in healthy, Western populations.

Insulin-like growth factor physiology: what we have learned from human studies

Although very similar to insulin and its receptor; the modus operandi of the insulin-like growth factors (IGFs) within the body is very different from that of the traditional peptide hormone. The IGF-binding proteins bind the IGFs with greater affinity than the cell surface receptors, enabling them to tightly control tissue activity. In addition to their role in fetal and childhood growth, IGFs play an important role in metabolic regulation. This article describes the basic underlying human physiology of IGFs, how this differs from that of experimental models, and why some information can only be learned from human clinical studies.

Tanning predicts bone mass but not structure in adolescent females living in Hawaii

OBJECTIVES

To evaluate the relationship between facultative skin pigmentation, which predicts circulating levels of plasma 25-hydroxymitamin D, and several measures of bone mass and structure in a cross sectional sample of adolescent females living in Hawaii.

METHODS

Our sample was composed of adolescent females (n = 94) living in Hawaii where seasonal sun exposure is minimal, and who self-identified as either white (n = 16) or Asian (n = 78). Bone mineral content (BMC) of the total body, the lumbar spine and the hip, and cross sectional area (CSA) and section modulus (Z) at the proximal femur were quantified using DXA. Facultative skin pigmentation was measured at the forehead and non-facultative skin pigmentation was measured at the inner arm using a Chroma Meter CR-200b colorimeter.

RESULTS

There were no significant differences between ethnic groups in terms of skin pigmentation. The difference between a* taken at the forehead and inner upper arm significantly predicted BMC at the lumbar spine, total hip, and total body. Other measures of skin pigmentation were not significant predictors of any other measure of skeletal integrity.

CONCLUSIONS

The difference between facultative and non-facultative skin pigmentation for a* is a significant predictor BMC, but not bone structure. Our findings are limited by an inability to control for long term UVA and UVB exposure and lack of a measure of serum 25(OH)D status. Further research is needed to examine these questions, particularly in populations who live at high latitudes where a winter season limits vitamin D(3) synthesis.

Vitamin D supplementation for improving bone mineral density in children

BACKGROUND

Results of randomised controlled trials (RCTs) of vitamin D supplementation to improve bone density in children are inconsistent.

OBJECTIVES

To determine the effectiveness of vitamin D supplementation for improving bone mineral density in children, whether any effect varies by sex, age or pubertal stage, the type or dose of vitamin D given or baseline vitamin D status, and if effects persist after cessation of supplementation.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL Issue 3, 2009), MEDLINE (1966 to present), EMBASE (1980 to present), CINAHL (1982 to present), AMED (1985 to present) and ISI Web of Science (1945 to present) on 9 August 2009, and we handsearched key journal conference abstracts.

SELECTION CRITERIA

Placebo-controlled RCTs of vitamin D supplementation for at least three months in healthy children and adolescents (aged from one month to < 20 years) with bone density outcomes.

DATA COLLECTION AND ANALYSIS

Two authors screened references for inclusion, assessed risk of bias, and extracted data. We conducted meta-analyses and calculated standardised mean differences (SMD) of the percent change from baseline in outcomes in treatment and control groups. We performed subgroup analyses by sex, pubertal stage, dose of vitamin D and baseline serum vitamin D and considered these as well as compliance and allocation concealment as possible sources of heterogeneity.

MAIN RESULTS

We included six RCTs (343 participants receiving placebo and 541 receiving vitamin D) for meta-analyses. Vitamin D supplementation had no statistically significant effects on total body bone mineral content (BMC), hip bone mineral density (BMD) or forearm BMD. There was a trend to a small effect on lumbar spine BMD (SMD 0.15, 95% CI -0.01 to 0.31, P = 0.07). There were no differences in effects between high and low serum vitamin D studies at any site though there was a trend towards a larger effect with low vitamin D for total body BMC (P = 0.09 for difference). In low serum vitamin D studies, significant effects on total body BMC and lumbar spine BMD were approximately equivalent to a 2.6% and 1.7 % percentage point greater change from baseline in the supplemented group.

AUTHORS' CONCLUSIONS

These results do not support vitamin D supplementation to improve bone density in healthy children with normal vitamin D levels, but suggest that supplementation of deficient children may be clinically useful. Further RCTs in deficient children are needed to confirm this.

Maximizing bone mineral mass gain during growth for the prevention of fractures in the adolescents and the elderly

Bone mass is a key determinant of fracture risk. Maximizing bone mineral mass during childhood and adolescence may contribute to fracture risk reduction during adolescence and possibly in the elderly. Although more than 60% of the variance of peak bone mass (PBM), the amount of bone present in the skeleton at the end of its maturation process, is genetically determined, the remainder is likely influenced by factors amenable to positive intervention, such as adequate dietary intake of dairy products as a natural source of calcium and proteins, vitamin D, and regular weight-bearing physical activity. Low calcium and vitamin D intakes are associated with negative effects on bone, including suboptimal PBM acquisition. As suggested by intervention studies, regular intake of dairy products may have positive and possibly sustained effects on bone mineral mass gain, contributing thereby to fracture risk reduction. Further evidence from intervention studies suggests that weight-bearing physical activities, such as jumping, may contribute to bone mineral mass gain in children. Optimizing PBM acquisition through dietary and physical exercise measures may represent a valuable primary method for the prevention of fractures.

Session 2: Other diseases: Dietary management of osteoporosis throughout the life course

Osteoporosis-related fractures have a major impact on health at the individual and societal levels, through associated morbidity and increased mortality. Up to 50% of women and 20% of men at age 50 years may have a fragility fracture in their remaining lifetimes. Nutrition is important throughout the life course. Thus, adequate Ca and vitamin D intake has been shown to reduce risk of fracture in old age. Other factors such as protein and vitamin K may also be important, although the evidence here is less strong. In childhood Ca or vitamin D supplementation trials have demonstrated modest short-term increases in bone mass, but the long-term implications have not been established. Over recent years it has become apparent that maternal nutrition may have critical and far-reaching persistent consequences for offspring health. Thus, reduced maternal fat stores and low levels of circulating 25-hydroxyvitamin D in pregnancy are associated with reduced bone mass in the offspring; placental Ca transport may be key to these relationships. Wider maternal dietary patterns have also been shown to predict offspring bone mass. These data suggest that an interventional approach aimed at specific micronutrients, such as vitamin D, should be complemented by general optimisation of the mother's diet and lifestyle in order to maximise intrauterine bone mineral accrual and postnatal skeletal growth and thus reduce the burden of osteoporotic fractures in future generations.

Milk consumption and circulating insulin-like growth factor-I level: a systematic literature review

Studies suggest that the circulating insulin-like growth factor I (IGF-I) level is positively associated with the prostate cancer risk. The association of milk consumption and circulating IGF-I level has been examined in epidemiological studies with inconsistent results. We conducted a systematic literature review to summarize and quantify the current evidence for milk or dairy product consumption and the circulating IGF-I level. We searched relevant papers published in English up to March 2009 in various databases. Fifteen cross-sectional studies and eight randomized controlled trials were finally identified. Ten cross-sectional studies showed statistically positive correlation between milk consumption and the circulating IGF-I level. Randomized controlled trials indicated that the circulating IGF-I level was significantly higher in the milk intervention group. After meta-analysis, the weighted mean difference of the circulating IGF-I level was 13.8 ng/ml (95% confidence interval: 6.1-21.5 ng/ml) comparing the intervention group with the control group. The current evidence suggests that milk consumption may increase the circulating IGF-I level.

Dairy consumption and female height growth: prospective cohort study

BACKGROUND

Because of its nutrients and anabolic hormones, cow's milk may promote height growth, which in turn has been related to breast cancer risk. We prospectively investigated associations between dairy intakes and height growth.

METHODS

A cohort of 5,101 girls from throughout the United States completed annual surveys (1996-2001, 2003), providing height, weight, and past-year diet. At baseline, all were premenarchal, ages 9 years and above, with no serious medical conditions. We studied three outcomes: annual height growth, peak growth velocity, and adult height. Multivariate models estimated the effects of milk, cheese, yogurt, and energy on subsequent growth, adjusted for race/ethnicity, age, prior height, and body mass index. Other models studied fats and proteins.

RESULTS

Premenarchal girls who drank >3 servings per day of milk grew 0.11 in. (P = 0.02) more the following year than girls consuming <1 serving per day. Yogurt (+0.13 in./cup; P = 0.02), but not cheese or total calories, predicted height growth. In a separate model, dairy protein (+0.034 in./10 g; P < 0.001) predicted height growth. Larger peak velocities were seen among girls reporting, at baseline, more milk (>3 glasses per day versus <1; +0.14 in., P = 0.01), more yogurt (+0.17 in./cup, P = 0.02), and, in a separate model, more dairy protein (+0.039 in./10 g; P = 0.003). Baseline milk and dairy protein predicted taller adults. Dairy protein was more important than dairy fat, for all outcomes. Nondairy animal protein and vegetable protein were never significant, nor were nondairy animal fat and vegetable fat.

CONCLUSION

Of the foods/nutrients studied, dairy protein had the strongest association with height growth. These findings suggest that a factor in the nonlipid phase of milk, but not protein itself, has growth-promoting action in girls.

Nutrition: its role in bone health

At a given age, bone mass is determined by the amount of bone accumulated at the end of skeletal growth (the so-called peak bone mass), and by the amount of bone lost subsequently. Nutritional intake is an environmental factor that influences both bone capital accumulation, which is fully achieved by the end of the second decade of life, and bone loss, which occurs during the second half of existence. Nutrients may act directly by modifying bone turnover, or indirectly via changes in calciotropic hormone secretion. The study of the association between nutrition and a bone phenotypic expression may provide inconsistent results, in part because of the low accuracy and reproducibility of the various tools used to assess dietary intakes. Sufficient dietary calcium and protein are necessary for bone health during growth as well as in the elderly.

Vitamin D: a growing perspective

Vitamin D deficiency has been widely reported in all age groups in recent years. Rickets has never been eradicated in developed countries, and it most commonly affects children from recent immigrant groups. There is much evidence that current vitamin D guidelines for the neonatal period, 5-10 microg (200-400 IU)/day, prevent rickets at the typical calcium intakes in developed countries. The annual incidence of vitamin D-deficiency rickets in developed countries ranges between 2.9 and 7.5 cases per 100,000 children. The prevalence of vitamin D deficiency in mothers and their neonates is remarkable, and the results of one study suggest that third-trimester 25-hydroxyvitamin D (25(OH)D) is associated with fetal bone mineral accrual that may affect prepubertal bone mass accumulation. Beyond infancy, the evidence indicates that 5 microg (200 IU)/day of vitamin D has little effect on vitamin D status as measured by the serum 25(OH)D concentration. Two randomized clinical trials show that higher vitamin D intake improves one-year gain in bone density in adolescent girls. The functions of vitamin D extend beyond bone to include immune system regulation and anti-proliferative effects on cells. Early life vitamin D inadequacy is implicated in the risk of bone disease, autoimmune disease, and certain cancers later in life; however, long-term interventional studies do not exist to validate the widespread implementation of greater vitamin D consumption. Here we review the available data concerning vitamin D status and health effects of vitamin D in pregnancy through to and including adolescence.

Dietary protein intake and bone mineral content in adolescents-The Copenhagen Cohort Study

Data indicate that various protein sources may exhibit a differential effect on bone metabolism. We investigated associations of milk and meat protein intake with bone mineral content (BMC) in adolescents. Milk, but not meat, protein intake was positively associated with size-adjusted BMC. Milk-derived protein may be beneficial for bone mineralization.

INTRODUCTION

Milk and meat protein intake has been reported to exhibit a differential effect on serum insulin-like growth factor-I (IGF-I). IGF-I plays a key role in bone metabolism. Therefore, we investigated associations of different protein sources with BMC and bone area (BA) in adolescents.

METHODS

This was a cross-sectional study of 17-year-old girls (n = 63) and boys (n = 46) participating in the second follow-up of The Copenhagen Cohort Study. We measured dietary intake (7-day food record), BMC and BA (dual-energy X-ray absorptiometry), serum markers for bone turnover and serum IGF-I (immunoassays).

RESULTS

The mean total protein intake ( approximately 1.2 g/kg) was modestly higher than that recommended. Total and milk ( approximately 0.3 g/kg) protein intake, but not meat protein intake ( approximately 0.4 g/kg), was positively associated with size-adjusted BMC (P <or= 0.05). The positive association between milk protein intake and size-adjusted BMC remained significant after correction for energy, calcium, and physical activity (P <or= 0.01) and did not seem to be mediated via current serum IGF-I. None of the analyzed protein sources was significantly associated with size-adjusted BA.

CONCLUSIONS

Our results suggest that some components of milk protein may promote bone mineralization. Further studies are needed to elucidate this phenomenon.

Realist review to understand the efficacy of school feeding programmes

A recent Cochrane review found that school feeding programmes significantly improve the growth and cognitive performance of disadvantaged children. Trisha Greenhalgh,Elizabeth Kristjansson, and Vivian Robinson look more closely at the highly heterogeneous trials to see what works, for whom, and in what circumstances

Milk consumption during pregnancy is associated with increased infant size at birth: prospective cohort study

BACKGROUND

Cow milk contains many potentially growth-promoting factors.

OBJECTIVE

The objective was to examine whether milk consumption during pregnancy is associated with greater infant size at birth.

DESIGN

During 1996-2002, the Danish National Birth Cohort collected data on midpregnancy diet through questionnaires and on covariates through telephone interviews and ascertained birth outcomes through registry linkages. Findings were adjusted for mother's parity, age, height, prepregnant BMI, gestational weight gain, smoking status, and total energy intake; father's height; and family's socioeconomic status The analyses included data from 50,117 mother-infant pairs.

RESULTS

Mean (+/-SD) consumption of milk was 3.1 +/- 2.0 glasses/d. Milk consumption was inversely associated with the risk of small-for gestational age (SGA) birth and directly with both large-for-gestational age (LGA) birth and mean birth weight (P for trend < 0.001). In a comparison of women drinking >or=6 glasses/d with those drinking 0 glasses/d, the odds ratio for SGA was 0.51 (95% CI: 0.39, 0.65) and for LGA was 1.59 (1.16, 2.16); the increment in mean birth weight was 108 g (74, 143 g). We also found graded relations (P < 0.001) for abdominal circumference (0.52 cm; 0.35, 0.69 cm), placental weight (26 g; 15, 38 g), birth length (increment: 0.31 cm; 0.15, 0.46 cm), and head circumference (0.13 cm; 0.04, 0.25 cm). Birth weight was related to intake of protein, but not of fat, derived from milk.

CONCLUSION

Milk intake in pregnancy was associated with higher birth weight for gestational age, lower risk of SGA, and higher risk of LGA.

Milk consumption and the prepubertal somatotropic axis

BACKGROUND

Nutrients, hormones and growth factors in dairy foods may stimulate growth hormone (GH), insulin-like growth factor I (IGF-I), and raise the ratio of IGF-I to its binding protein, IGFBP-3. We conducted pilot studies in Mongolia and Massachusetts to test the extent to which milk intake raised somatotropic hormone concentrations in prepubertal children.

METHODS

In Ulaanbaatar, we compared plasma levels before and after introducing 710 ml daily whole milk for a month among 46 10-11 year old schoolchildren. In a randomized cross-over study in Boston, we compared plasma hormone levels of 28 6-8 year old girls after one week of drinking 710 ml low fat (2%) milk with their hormone levels after one week of consuming a macronutrient substitute for milk.

RESULTS

After a month of drinking whole milk, Mongolian children had higher mean plasma levels of IGF-I (p < 0.0001), IGF-I/IGFBP-3 (p < 0.0001), and 75th percentile of GH levels (p = 0.005). After a week of drinking low fat milk, Boston girls had small and non-significant increases in IGF-1, IGF-1/IGFBP-3 and GH.

CONCLUSION

Milk drinking may cause increases in somatotropic hormone levels of prepubertal girls and boys. The finding that milk intake may raise GH levels is novel, and suggests that nutrients or bioactive factors in milk may stimulate endogenous GH production.