Vitamin D is a fat soluble vitamin that it needed for the normal growth and development of bone in children and the maintenance of bone growth in adults1. Vitamin D contributes to normal absorption/utilisation of calcium and phosphorus, blood calcium levels, function of the immune system, as well as playing a role in process of cell division1. Vitamin D also contributes to the maintenance of normal bones, muscle function and teeth1.
Babies are born with a certain level of vitamin D. Their vitamin D level depends on the amount of vitamin D transferred from the mother at birth. In breastfed babies vitamin D levels depend on a combination of the amount of vitamin D consumed in the mothers’ diet and the mothers’ production of vitamin D by the skin through exposure to sunlight2. The level of Vitamin D transferred from the mother at birth falls dramatically after 3-4 weeks unless additional sources are made available3. In the general population it is thought that the intake of vitamin D is below the recommended amount4, indeed in northerly latitudes such as the Ireland it is thought that optimal transfer of vitamin D to a baby may not occur due to poor maternal vitamin D status in pregnancy.5,6,7,8
Vitamin D deficiency was thought to have been eradicated in Ireland after the Second World War, due to better nutrition. However, over 20 cases of rickets in infants and toddlers have been reported at two Dublin hospitals in the last four to five years. Further evidence is emerging that there is widespread low levels of vitamin D in the general population in Ireland. There are several factors which have contributed to this.
Vitamin D is mainly produced in the body by exposure of the skin to sunlight. However, because of Ireland’s northerly latitude, in the months between November and March there is inadequate quality and quantity of sunlight to enable sufficient production of vitamin D by the body (the current recommended dietary daily amount of vitamin D is 5 µg)8. Even on sunny days in the winter, the sun’s rays are of the wrong type for the production of vitamin D. In addition, with more people working indoors and using sunscreen when outside, vitamin D from sunlight exposure has decreased. Darker skinned people living in Ireland are particularly at risk as they require more sunlight to produce vitamin D (10 to 50 times more exposure to sunlight required). Also, some religious practices preclude any skin exposure.
Dietary sources of vitamin D are not consumed in sufficient quantities to counter the lack of sunlight exposure and do not form part of the weaning diet for infants. Examples of dietary sources of vitamin D include oily fish (e.g. salmon, mackerel, sardines), egg yolks and fortified foods such as milk and breakfast cereals. In addition, offal meat such as liver and kidney are a good source of Vitamin D but these foods are not suitable for infants and pregnant women because they provide too much Vitamin A.
1 Commission Regulation (EU) No: 432/2012 of 16 May 2012
2 Kovacs, CS and Kronenberg HM. (1997) Maternal-fetal calcium and bone metabolism during pregnancy, puerperium, and lactation. Endocr Rev, 18(6):832-72
3 Suskind, DL. (2009) Nutritional deficiencies during normal growth. Pediatr Clin North Am, 56(5):1035-53
4 Morgan et al. (2008) SLÁN 2007: Survey of Lifestyle, Attitudes & Nutrition in Ireland. Main Report. Dublin: Department of Health and Children
5 McGowan et al. 2011 (unpublished)
6 Holmes et al. (2009) Vitamin D deficiency and insufficiency in pregnant women: a longitudinal study.Br J Nutr, 102(6):876-81
7 O’Riordan et al. (2008) Prevalence of suboptimal vitamin D status during pregnancy. Ir Med J: 101 (8):240, 242-3
8 Food Safety Authority of Ireland (2013) Q&A on Vitamin D report Recommendation for a National Policy of Vitamin D supplementation for Infants in Ireland.