Soft drink and milk consumption, physical activity, bone mass, and upper limb fractures in children: a population-based case-control study

Effects of soft drink consumption on nutrition and health: a systematic review and meta-analysis

In a meta-analysis of 88 studies, we examined the association between soft drink consumption and nutrition and health outcomes. We found clear associations of soft drink intake with increased energy intake and body weight. Soft drink intake also was associated with lower intakes of milk, calcium, and other nutrients and with an increased risk of several medical problems (e.g., diabetes). Study design significantly influenced results: larger effect sizes were observed in studies with stronger methods (longitudinal and experimental vs cross-sectional studies). Several other factors also moderated effect sizes (e.g., gender, age, beverage type). Finally, studies funded by the food industry reported significantly smaller effects than did non-industry-funded studies. Recommendations to reduce population soft drink consumption are strongly supported by the available science.

Nutrition and bone growth and development

The growth and development of the human skeleton requires an adequate supply of many different nutritional factors. Classical nutrient deficiencies are associated with stunting (e.g. energy, protein, Zn), rickets (e.g. vitamin D) and other bone abnormalities (e.g. Cu, Zn, vitamin C). In recent years there has been interest in the role nutrition may play in bone growth at intakes above those required to prevent classical deficiencies, particularly in relation to optimising peak bone mass and minimising osteoporosis risk. There is evidence to suggest that peak bone mass and later fracture risk are influenced by the pattern of growth in childhood and by nutritional exposures in utero, in infancy and during childhood and adolescence. Of the individual nutrients, particular attention has been paid to Ca, vitamin D, protein and P. There has also been interest in several food groups, particularly dairy products, fruit and vegetables and foods contributing to acid-base balance. However, it is not possible at the present time to define dietary reference values using bone health as a criterion, and the question of what type of diet constitutes the best support for optimal bone growth and development remains open. Prudent recommendations (Department of Health, 1998; World Health Organization/Food and Agriculture Organization, 2003) are the same as those for adults, i.e. to consume a Ca intake close to the reference nutrient intake, optimise vitamin D status through adequate summer sunshine exposure (and diet supplementation where appropriate), be physically active, have a body weight in the healthy range, restrict salt intake and consume plenty of fruit and vegetables.

A genetic approach to fracture epidemiology in childhood

The purpose of this report is to provide a review of both childhood fracture epidemiology and known heritable causes for fracture predisposition to the Medical Geneticist, who is frequently consulted to assess children with multiple or unexplained fractures for a physiologic etiology. A detailed knowledge of the clinical and laboratory evaluation for osteogenesis imperfecta (OI) and other single-gene disorders is obviously essential to complete a useful evaluation of such children. The experienced clinician will immediately recognize that single gene disorders represent only a small fraction of these patients. In infants, non-accidental trauma (NAT) unfortunately is the likely explanation for the fracture pattern, but in some infants, and certainly in older children with recurrent fractures, no medical explanations can be found. Recent studies in which bone mineral density (BMD) has been associated with genetic variation at a number of candidate genes are promising but these studies are too premature yet to be used clinically. Nonetheless, we do expect that in the future whole-genome approaches in conjunction with key clinical and epidemiological variables may be combined through an informatics approach to create better predictors of fracture susceptibility for these populations of patients.

Calcium supplementation for improving bone mineral density in children

BACKGROUND

Clinical trials have shown that calcium supplementation in children can increase bone mineral density (BMD) although this effect may not be maintained. There has been no quantitative systematic review of this intervention.

OBJECTIVES

. To determine the effectiveness of calcium supplementation for improving BMD in children. . To determine if any effect varies by sex, pubertal stage, ethnicity or level of physical activity, and if any effect persists after supplementation is ceased.

SEARCH STRATEGY

We searched CENTRAL, (Cochrane Central Register of Controlled Trials) (Issue 3, 2005), MEDLINE (1966 to 1 April 2005), EMBASE (1980 to 1 April 2005), CINAHL (1982 to 1 April 2005), AMED (1985 to 1 April 2005), MANTIS (1880 to 1 April 2005) ISI Web of Science (1945 to 1 April 2005), Food Science and Technology Abstracts (1969 to 1 April 2005) and Human Nutrition (1982 to 1 April 2005). Conference abstract books (Osteoporosis International, Journal of Bone and Mineral Research) were hand-searched.

SELECTION CRITERIA

Randomised controlled trials of calcium supplementation (including by food sources) compared with placebo, with a treatment period of at least 3 months in children without co-existent medical conditions affecting bone metabolism. Outcomes had to include areal or volumetric BMD, bone mineral content (BMC), or in the case of studies using quantitative ultrasound, broadband ultrasound attenuation and ultrasonic speed of sound, measured after at least 6 months of follow-up.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data including adverse events. We contacted study authors for additional information.

MAIN RESULTS

The 19 trials included 2859 participants, of which 1367 were randomised to supplementation and 1426 to placebo. There was no heterogeneity in the results of the main effects analyses to suggest that the studies were not comparable. There was no effect of calcium supplementation on femoral neck or lumbar spine BMD. There was a small effect on total body BMC (standardised mean difference (SMD) +0.14, 95% CI+0.01, +0.27) and upper limb BMD (SMD +0.14, 95%CI +0.04, +0.24). Only the effect in the upper limb persisted after supplementation ceased (SMD+0.14, 95%CI+0.01, +0.28). This effect is approximately equivalent to a 1.7% greater increase in supplemented groups, which at best would reduce absolute fracture risk in children by 0.1-0.2%per annum. There was no evidence of effect modification by baseline calcium intake, sex, ethnicity, physical activity or pubertal stage. Adverse events were reported infrequently and were minor.

AUTHORS' CONCLUSIONS

While there is a small effect of calcium supplementation in the upper limb, the increase in BMD which results is unlikely to result in a clinically significant decrease in fracture risk. The results do not support the use of calcium supplementation in healthy children as a public health intervention. These results cannot be extrapolated to children with medical conditions affecting bone metabolism.

Children who experience their first fracture at a young age have high rates of fracture

Rate of fracture was examined according to age at first fracture in 313 New Zealand children (145 girls, 168 boys) under l3 years of age (95.4% of a consecutive series of children treated at one hospital for a recent confirmed fracture at any site). In their lifetimes they had experienced 468 separate fracture events, over half (54.7%) occurring in the 32.3% of children breaking bones on more than one occasion. Children experiencing a first fracture before 4 years of age had 36.7 (95%CI 30.7-44.1) fractures per l00 years of exposure: this was a significantly higher rate than that of children experiencing their first fracture later in life. Thus, using the <4.0 year age group as a reference, we found that rate ratios (adjusted for gender) for groups that had suffered the first fracture at later ages were: first fracture between 4.0 and 6.99 years, 0.77 (95%CI 0.58-1.03); first fracture between 7.0 and 9.99 years, 0.63 (95%CI 0.42-0.94); first fracture between 10.0 and 12.99 years, 0.48 (95% CI 0.32-0.72). Asthma was over-represented (31% seen, 25% expected), and a high proportion of the sample (32.9%) used corticosteroid medications; however, neither characteristic affected age at first fracture. In contrast, the large number (n= 42) of youngsters (13.4% of the sample) reporting adverse reactions to milk were younger at first fracture than children without reactions to milk (P<0.05). We conclude that children experiencing their first fracture at a young age have high rates of fracture and should be targeted for advice to improve their bone strength.

Growth, children, and fractures

Fractures in childhood have long been considered an unavoidable consequence of growth. Studies in recent years have documented the epidemiology of these very common fractures and have also documented considerable variation by fracture type and from country to country. There have also been a number of studies aimed at identifying risk factors particularly for the most common distal forearm fracture. These studies have consistently associated bone mineral density with these fractures. Other possible risk factors include obesity, physical inactivity, sports, cola beverages, calcium intake, risk taking, and coordination. While prospective studies are required to confirm these risk factors, accumulating evidence now suggests that a substantial proportion of fractures in children are preventable.