The following news story appeared in Essentially MIDIRS, vol 4, no 5, May 2013, p24.
Some interesting results have emerged over the years from the long-term health research project, the Avon Longitudinal Study of Parents and Children (ALSPAC), also known as Children of the 90s. The latest research to be published examines the effects of mothers’ vitamin D levels in pregnancy on the bone health of their offspring.
The study, published in the Lancet (Lawlor et al 2013), assessed vitamin D levels in 3960 pregnant women in each of the three trimesters of pregnancy and compared this data with the bone mineral content of their children just before they reached ten years old. The study suggested no significant association between maternal levels of vitamin D and the bone mineral content of her child.
The study’s findings call into question NICE guidelines which recommend that pregnant and breastfeeding women should take supplements of ten micrograms of vitamin D every day to ensure healthy bone formation and development in their child. Lead researcher, Professor Lawlor, did however, acknowledge that the study didn’t examine any other effects, adverse or beneficial, of taking vitamin D supplements.
Professor Philip Steer, Emeritus Professor in Obstetrics and Gynaecology at Imperial College London stated that, ‘In view of the inconsistency in results [of previous studies], it might seem unclear why vitamin D supplementation is officially recommended for all pregnant and breastfeeding women.’ He suggested that only those at greatest risk (women of certain ethnicities, with limited exposure to sunlight, or those with a diet low in vitamin D) should be offered routine supplementation as a precaution, and stressed the need for a long-term randomised controlled trial of supplementation.
This study came hot on the heels of another study of vitamin D levels in pregnant women (Weisse et al 2013) published in Allergy which suggested that pregnant women should actually avoid taking vitamin D supplements because supplementation raises the risk of their offspring developing a food allergy.
This second study used samples from a cohort in Germany gathered between 2006 and 2008, and involved 622 mothers and their 629 children. Blood samples were taken from the women and cord blood from their children to discover vitamin D levels in both. As expected, children of mothers with high levels of vitamin D in their blood were found to have higher levels in their own blood and follow-up questionnaires over the first two years of their lives found that these children had high levels of specific immunoglobulin E to food allergens such as egg white, milk protein, wheat flour, peanuts and soya beans.
The lead author, Dr Kristin Weisse, highlighted the fact that other factors that raise vitamin D levels, such as the season, exposure to the sun and the amount of time spent outdoors were taken into consideration by the study. She also stated that there are many other factors involved in the occurrence of food allergies, but nevertheless would advise pregnant women not to take vitamin D supplements because, ‘Based on our information, an excess of vitamin D can increase the risk of children developing a food allergy in the first two years of their life.’
When considered together, these studies emphasise that routine supplementation is not the panacaea that it is sometimes thought to be, Dr Tony Falconer, president of the Royal College of Obstetricians and Gynaecologists stated, ‘Further research is needed to look at vitamin supplementation including potential benefits, harms and optimal dosing.’
Lawlor DA, Wills AK, Fraser A et al (2013). Association of maternal vitamin D status during pregnancy with bone-mineral content in offspring: a prospective cohort study. Lancet, 19 March. [Online ahead of print].
Weisse K, Winkler S, Hirche F et al (2013). Maternal and newborn vitamin D status and its impact on food allergy development in the German LINA cohort study. Allergy 68(2): 220-8.