Biosocial birth cohort studies are uniquely positioned to be novel sites of interdisciplinary research. Their enduring commitment to specific field sites and populations, recurring grant renewal cycles, ability to ask prospective questions while drawing on long-standing data repositories, and more ensure ongoing collaboration and allow research to remain responsive to the evolving needs and timelines of multiple disciplines. However, it is widely recognised that interdisciplinary work is often easier imagined than achieved, and additional conditions are required to facilitate it beyond assembling teams of varied experts. This piece offers mediating practices as a concept that refers to the practical, multi-directional, and relational processes that attempt to resolve tensions that interdisciplinary teams often confront. Mediating practices bridge gaps among different disciplines’ data and methods, often relying on pragmatic strategies, like re-designing data infrastructures or planning action items after a meeting, to do so. As such, mediating practices are crucial to conducting successful interdisciplinary research. Further, the concept of mediating practices foregrounds the actions of junior team members who often perform these practices, highlighting the need to foster epistemic humility and models of horizontal knowledge production in interdisciplinary teams. Here, the authors discuss their experiences and insights as members of interdisciplinary projects and outline how mediating practices emerged in these projects and enabled interdisciplinary success.

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.

The impact of variations in current infant feeding practice on bone mineral accrual is not known. We examined the associations between duration of breast-feeding and compliance with infant dietary guidelines and later bone size and density at age 4 years. At total of 599 (318 boys) mother–child pairs were recruited from the Southampton Women's Survey. Duration of breast-feeding was recorded and infant diet was assessed at 6 and 12 months using FFQ. At 6 and 12 months the most important dietary pattern, defined by principal component analysis, was characterised by high consumption of vegetables, fruits and home-prepared foods. As this was consistent with infant feeding recommendations, it was denoted the ‘infant guidelines’ pattern. At age 4 years, children underwent assessment of whole-body bone size and density using a Hologic Discovery dual-energy X-ray absorptiometry instrument. Correlation methods were used to explore the relationships between infant dietary variables and bone mineral. There was no association between duration of breast-feeding in the first year of life and 4-year bone size or density. ‘Infant guidelines’ pattern scores at 6 and 12 months were also unrelated to bone mass at age 4 years. We observed wide variations in current infant feeding practice, but these variations were not associated with differences in childhood bone mass at age 4 years.