• Maintaining a high vitamin D level during pregnancy is important for the developing baby.  All women are recommended to take vitamin D supplements when they are pregnant, but a recent study from the University of Southampton has shown that a woman’s genes are also an important determinant of her vitamin D level.

    Researchers from the Medical Research Council Lifecourse Epidemiology Unit (MRC LEU) at the University of Southampton examined genetic differences in blood samples from nearly 700 women, who had participated in the MAVIDOS trial, a randomised placebo-controlled study of vitamin D supplementation in pregnancy.  Half the women had received vitamin D and half had received a dummy tablet whilst they were pregnant.

    The results, published in the Journal of Clinical Endocrinology and Metabolism, showed that common variation in the genes was related to the women’s vitamin D level in their blood both before and after receiving the supplement, but these differed before and after supplementation.   Vitamin D can be made by the action of sunlight on the skin or obtained from the diet.  Before receiving the vitamin D supplement, a small difference in gene that controls the production of an enzyme that makes vitamin D in the skin determined vitamin D level in the blood.  After taking the vitamin D supplement, common differences in two genes that produce an enzyme to activate vitamin D and for a protein which transports vitamin D in the blood were related to vitamin D level.

    Nicholas Harvey, Professor of Rheumatology and Clinical Epidemiology at the MRC LEU, University of Southampton led the study with Dr Rebecca Moon, Clinical Research Fellow. He said:

    We know it is important to optimize vitamin D levels in pregnancy.  We have previously shown the vitamin D supplementation increases vitamin D levels but the level achieved is highly variable from woman to woman.  This study provides exciting insights into how common genetic markers contribute to this variation- these findings might allow us to more accurately prescribe vitamin D supplementation for each individual in the future.

    Professor Cyrus Cooper, Director, and Professor of Rheumatology at the MRC Lifecourse Epidemiology Unit, University of Southampton said:

    This work forms part of a larger programme of research at the MRC Lifecourse Epidemiology Unit, University of Southampton, addressing the early life determinants of bone development, and will inform novel strategies, such as gestational vitamin D supplementation, aimed at improving bone health across future generations.