“In this prospective cohort study, ever breast-feeding as compared with never breast-feeding was positively associated with bone mass in six-year-old children, but exclusive breast-feeding for 4 months or longer was not positively associated with childhood bone outcomes,” the authors from the University Medical Center Rotterdam wrote.
Early life nutrition is an important factor in achieving peak bone mass in adulthood and future risk of osteoporosis. Components of breast milk may be beneficial to bone development but some nutrients such as calcium and vitamin D may be higher in formula milk.
Writing in the British Journal of Nutrition, the scientists said it could be speculated that late introduction of micronutrients present in solid foods may be adversely related to bone development, also early introduction of solids has been linked to increased risk of obesity which may positively influence bone development through mechanical loading by body weight.
Although the present study results do not support a beneficial effect of exclusive breastfeeding for longer than four months, the scientists were keen to point out they had no detailed information on frequency and quantity of solid foods consumed and there was no evidence for a dose-response relationship.
Nearly 5000 children were studied as part of the Generation R study, a Netherlands population-based prospective cohort study from foetal life onwards. Information was collected from the mothers by questionnaire about breastfeeding duration and exclusiveness, and timing of introduction of solid foods.
The bones of the study
A dual-energy X-ray absorptiometry scan was performed on the children at six years of age and bone mineral density (BMD), bone mineral content (BMC) and bone area (BA) were analysed. Results were adjusted for vitamin D supplementation.
Children who had never been breast fed had lower BMD, BMC and BA compared to children who had at some point ('ever') been breastfed.
However, children who had received formula milk or solid foods in addition to breast milk within the first four months of life had higher BMD and BMC and lower BA compared to children who were breast fed exclusively.
Breast-feeding for longer than four months was not associated with more positive bone outcomes, they found.
Introduction of solids before the age of four months was associated with a higher BMD and BMC, compared to introduction after this age.
The authors said additional confounding factors, further bone assessment techniques, and collection of fracture events may be factors to consider in future studies. Socio-demographic and lifestyle factors may also have influenced some of the results.
“Further research in other populations is needed to confirm our findings. In addition, future studies should investigate the underlying mechanisms and evaluate whether the observed differences have consequences for bone health in later life,” they wrote.
Source: British Journal of Nutrition
Published online ahead of print, doi:10.1017/S0007114515005462
“Associations of breast-feeding patterns and introduction of solid foods with childhood bone mass: The Generation R Study”
Authors: E.H. van den Hooven et al.