Influence of vitamin D on non-communicable disease outcomes in South African schoolchildren: the ViDiKids-NCD sub-study

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'Non-communicable disease' (NCD) is a term used to describe any illness that is not caused by infections. NCDs are becoming more common worldwide, particularly among less wealthy city-dwellers living in lower- and middle-income countries such as South Africa. Most research on NCDs focuses on illnesses that primarily affect adults, such as heart disease and cancer. However, children are also affected by NCDs including thinning of the bones leading to fractures (broken bones), and reduced muscle mass. 20% of urban South African schoolchildren suffer a bone fracture by the age of 15, compared with 13% in England. There is an urgent need to identify a way to improve bone health and muscle mass in children.Low levels of vitamin D ('the sunshine vitamin') are common among children living in disadvantaged urban environments such as the townships around Cape Town, due to decreased time outdoors, poor diets and obesity (which leads to vitamin D being stored in fat so that it is not available to the organs that need it). A growing body of research suggests that low levels of vitamin D may be a risk factor for developing thinning of the bones and reduced muscle mass. However, there is a lack of large, well-conducted research studies designed to find out whether vitamin D supplementation could strengthen children's bones and boost their muscle mass.We are already conducting a large MRC-funded clinical trial (the ViDiKids study) in 5,400 Cape Town schoolchildren to see if vitamin D supplementation can prevent TB. In this application, we propose to conduct a sub-study in which we will measure additional outcomes including bone density, muscle mass and physical fitness in a sub-set of 400 children who are also taking part in the main VidiKids trial.2) Aims and objectivesThe aim of this research is to determine whether a weekly vitamin D supplement, taken by mouth for 3 years, can improve bone density, muscle mass and physical fitness in children living in townships around Cape Town. We will achieve this by conducting a sub-study in 400 children. At the start of the sub-study we will measure participants' bone density, muscle mass and physical fitness. Participants will then be allocated to receive weekly doses of vitamin D or placebo (dummy medication) at random, supervised by study staff. At the end of the study we will repeat assessments of bone density, muscle mass and physical fitness, and compare these outcomes between children who received vitamin D vs placebo over the previous 3 years.3) Potential applications and benefitsWe already know that improvements in bone density in children translate into reduced risk of bone fractures: if we show that bone density is boosted by vitamin D, then supplements could be routinely given to children to prevent bone fractures. 1 billion people worldwide have inadequate vitamin D levels: results of our study could therefore have global importance.Several groups could benefit from the study. Children could benefit from the discovery of a cheap, safe method of reducing their risk of fractures; public health doctors could benefit from the discovery of a new tool for control of non-communicable diseases; and medical researchers could benefit from new scientific insights into the effects of vitamin D on children's health.