The statement, which is published in the Medical Journal of Australia (MJA) by the Australian and New Zealand Bone and Mineral Society and Osteoporosis Australia, is aimed at vitamin D levels during pregnancy and in infants, children and adolescents specifically. The vitamin D levels of new-borns reflect those of their mother’s during pregnancy and at birth, 48% of whom had low levels when tested.
Many people in Britain take some form of vitamin D supplement, as the vitamin can mainly be sourced naturally from sunshine – which is something that we don’t get a lot of in this country! However, the Australian paper outlines advice about appropriate levels of both sun exposure, and vitamin D supplementation, for its nation’s citizens. Most Australians get more than 90% of their vitamin D through sun exposure of the skin.
When vitamin D is formed in your skin, your blood stream takes it up and transports it to your liver, where it is formed into 25-hydroxyvitamin D (25(OH)D), and then it is formed as an active hormone in your kidney. When you have a vitamin D test, it measures your concentration of 25(OH)D, and expressed it in terms of nanomoles per litre (nmol/L). The paper confirmed that your target blood level for adequate vitamin D is a 25(OH)D concentration of 50nmol/L or greater, even though many experts advocate for higher minimum targets, such as 75 or 80nmol/L.
But why do these opinions differ? Experts interpret research evidence differently, and this affects how decisions are made. There is also a problem because ‘usual’ levels of vitamin D vary according to season and to location, meaning that two different seasons or locations in Australia could have very different sun exposure. However, for the time-being, the authorities are sticking to their one-size-fits-all target levels of 50nmol/L.