Don’t forget the ‘D’ in ‘healthy start’
When we think of the factors that are essential to “a healthy start”, we must not forget Vitamin D. It is an essential nutrient at all stages of life, literally from the cradle to the grave, but recent figures from the Australian Bureau of Statistics highlight some issues of concern.
About 25% of Australians are vitamin D deficient and younger adults are more likely to be affected than their parents, perhaps because they are less likely to be taking supplements. Studies also suggest about 40% of Australian babies are being born to vitamin D deficient mothers.
While there is debate within the medical profession about exactly how much vitamin D we need, there is no doubt that an adequate vitamin D status is necessary for a number of the activities critical for life and our research is investigating these effects in areas as diverse as fetal development and rheumatoid arthritis and osteoporosis.
Vitamin D maintains blood calcium at appropriate levels to ensure muscles such as our heart and lungs are working properly. It is therefore important to realise that in many cases the benefits to health of an adequate vitamin D status require an adequate dietary intake of calcium. It has been recognised since the discovery of vitamin D that a severe deficiency causes rickets in children, which stops the development of a skeleton with the strength to support the growing body. However recent research – including that conducted in our laboratory – indicates that inadequate dietary calcium combined with adequate vitamin D can markedly weaken bone and increase the risk of fractures.
Another issue – and one currently creating some controversy – is the contribution of severe vitamin D deficiency or an inadequate dietary calcium intake to the incidence of multiple unexplained fractures in babies. These babies are suspected of being the victims of child abuse and a number of international court cases have led to children being taken away from parents. On appeal, however, further investigations have identified that the babies are suffering from rickets due to severe vitamin D deficiency and the courts have decided that, on the balance of probability, the fractures could have occurred with normal handling of the baby because of their weakened bones.
The diagnosis of rickets in children under the age of six months is very difficult and research is required to develop techniques to assist paediatric emergency physicians in these situations. A further complication of severe vitamin D deficiency arises from heart failure and sudden death of small babies.
Moderate vitamin D deficiency in children limits the increase in bone mineral content of the skeleton during growth that is required for a healthy skeleton in childhood and optimal skeletal health throughout life. Fractures in children occur more frequently in those with a lower bone mineral density. Just as importantly, however, risk of fractures throughout adulthood, and especially in our older years, is markedly dependent on the maximum bone mineral content achieved during growth. Consequently an adequate vitamin D status and dietary calcium intake throughout childhood is important for reducing the risk of developing osteoporosis, a disease of frail bones and fractures, later in life.
In collaboration, our recent research has also demonstrated that a low maternal vitamin D status is associated with adverse pregnancy outcomes. Pregnancy complications include preterm birth, preeclampsia, intrauterine growth restriction and gestational diabetes mellitus that together affect 25% of first pregnancies. These pregnancy complications predict lifelong morbidity and mortality for both mother and child. Expectant mothers with low vitamin D levels also have low maternal red cell folate and high homocysteine levels at 20 weeks’ gestation which is associated with intrauterine growth restriction, preeclampsia, gestational hypertension, gestational diabetes or deliver small for gestational age babies. Importantly, vitamin D supplementation during pregnancy has been shown to reduce C-reactive protein, a marker of inflammation, improve insulin sensitivity and reduce markers of oxidative stress suggesting a critical role for vitamin D in lowering the incidence of complications during pregnancy and associated morbidity and mortality.
Howard Morris is a Professor in Medical Sciences at UniSA. Paul Anderson is Head of our Musculoskeletal Biology Research Laboratory.
For more information on the Sansom Institute research activities please visit our webpage.