![]() While not low enough to produce rickets or osteomalacia, she and her team are currently investigating the possibility that such levels might be linked to other health problems. People with darker skin pigmentation have potentially lower levels because the natural pigment melanin acts as a sunscreen and reduces UV-B induced vitamin D production in the skin. To prevent severe vitamin D deficiency we need to have concentrations of 25(OH)D above 25 nanomoles per litre (nmol l -1) in the body’.Īccording to Hyppönen 15 per cent per cent of the Caucasian population in the UK, for example, has below 25 nmol l - 1 of 25(OH)D in the winter and around 90 per cent has less than 75 nmol l -1 which is still considered to be less than optimal. ![]() She explained to InfoChem, ‘Owing to a lack of UV-B in northern latitudes many people in these regions will have low levels of vitamin D in the winter. Not a problem if you live in the tropics, but in winter, at latitudes above 52º north, ie northern Europe and north-east US, the light does not contain enough UV-B to rearrange the vitamin D precursors in the skin.Įlina Hyppönen, a research scientist in epidemiology at the Institute of Child Health at University College London (UCL) is interested in the role that a vitamin D deficiency may have in various illnesses. The amount of vitamin D that can be synthesised in the body will be subject to seasonal variations in sunlight. ![]() The recommended daily allowance of this vitamin for 14 –18 year olds is 5 μg per day in the US, while in the UK 10 μg per day is recommended for certain ‘at risk’ groups such as pregnant and breast-feeding women.Īround 90 per cent of our vitamin D requirement is made in our skin, with just 10 per cent coming from the diet. Other sources such as margarine, some breakfast cereals, red meat and egg yolks, have lower levels, from 1–8 μg per 100 g. Oily fish is the most important dietary source of vitamin D, containing 5–10 micrograms (μg) per 100 g. Nowadays rickets is much less common because vitamin D is added to various foods, and more people are aware of the benefits of a balanced diet. At the beginning of the 20th century, over 80 per cent of children in the industrial cities of northern Europe and north-east US had rickets – partly because of poor diet but also because they weren’t getting enough sunlight to compensate. (Bone is made up of a network of collagen fibres impregnated with crystals of hydroxyapatite, Ca 5(PO 4) 3(OH).) Vitamin D deficiencyĪ shortage of vitamin D leads to rickets in children and osteomalacia in adults, both characterised by soft, deformed bones which cannot support the weight of the body. A lack of this compound reduces the uptake of these ions from the intestine and creates a shortage for bone growth. This compound – a hormone – works together with specific proteins to allow effective transport of calcium and phosphate ions through the blood. Once formed, vitamin D 3 is converted by enzymes in the liver and kidney to the more active 25-hydroxyvitamin D (25(OH)D).
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