Fractures during growth: potential role of a milk-free diet

Abstract

Dietary calcium deficiency may increase fracture risk. In girls, 29.4% of fracture cases and 11.8% of controls without fracture had a history of milk-free diet. The odds ratio (OR) for fracture with a milk-free diet in girls was 4.6, p < 0.01. In boys, 23% of cases and 19% of controls had a history of a milk-free diet; OR = 1.3, NS). A milk-free diet due to cow's milk allergy is associated with increased fracture risk in girls. An intake of calcium below the reference daily intake (RDI) of 800-1200 mg/day during growth is thought to increase fracture risk even though convincing evidence for this view is scarce. The paucity of evidence may be partly due to many trial participants being calcium replete. Children and adolescents with cow's milk allergy (CMA) avoid milk and have a calcium intake below the RDI. The aim of this study was to examine the association between consumption of a milk-free diet and fracture risk. In this case-control study conducted in Poland, 57 boys and 34 girls aged 2.5-20 years with fractures (cases) were randomly matched by age and sex with 171 boys and 102 girls without fractures (controls). Weight and height were examined using standard methods. Bone mineral density (BMD) and body composition were measured using dual-energy X-ray absorptiometry. Conditional logistic regression and Bayesian analyses were used to determine the proportion of the fracture risk attributable to a milk-free diet. In girls, 29.4% of cases and 11.8% of controls had a history of milk-free diet producing an odds ratio (OR) for fracture associated with a milk-free diet of 4.6 (95% confidence interval [CI]: 1.4-15.5, p < 0.01). In boys, 23% of cases and 19% of controls had a history of a milk-free diet; OR = 1.3 (95% CI: 0.6-2.7, NS). If the prevalence of CMA in the population is 5%, only 6.7% of the fractures occurring are attributable to CMA and the associated nutritional deficit. Cow's milk allergy is associated with increased fracture risk in girls. Whether this association is due to the illness, calcium deficit or a deficit in other milk nutrients is uncertain. These data suggest that the contribution of milk-free diet to fracture liability among children and adolescents is modest.