The Mysore Parthenon study in south India observed the vitamin D status of 630 expectant mothers. After they had given birth, their healthy babies “were followed up with repeat anthropometry, annually till the age of five years and every six months thereafter”.
Subsequently, the babies’ cognitive function during childhood (nine to 10 years of age) and adolescence (13 to 14 years of age) was assessed via “a series of neuropsychological tests applicable for use in school-aged children and related to specific cognitive domains (memory, attention, fluid reasoning)”.
The children were tested on learning, long- and short-term memory, retrieval, reasoning and visio-spatial abilities, language production, visuo-motor processing speed and coordination, and attention and concentration.
While it was found that girls scored higher than boys in tests for reasoning, attention, verbal fluency, reasoning and short-term memory, the study stated that in general, “maternal vitamin D status was unrelated to offspring cognitive function at both ages”.
Animal studies have shown an association between maternal vitamin D deficiency and poor cognitive function in offspring, with vitamin D being vital to neurodevelopment and function. However, this study was the first of its kind involving humans (in a developing country), and found that maternal vitamin D deficiency did not affect the children’s cognitive function.
The study found a 68% of the expectant mothers to be vitamin D deficient, likely due to a number of factors, namely: the generally conservative dress among Indian women, their darker skin pigmentation (limiting their absorption of vitamin D from sun exposure), and low dietary vitamin D intake. This was true of South Asians living in India as well as abroad.
Additionally, there are “differences in vitamin D metabolism in Asian Indians”. According to in vitro studies, “tissue fibroblasts have increased 25-hydroxy-24-hydroxylase activity, leading to increased catabolism of activated vitamin D and therefore, an increased risk of developing vitamin D deficiency”.
Furthermore, among the study’s participants who were recruited when they were six to eight months pregnant, “very few were taking supplements”, and “women who took supplements in early pregnancy might have stopped taking them by 30 weeks”. This was despite obstetricians commonly prescribing vitamin D and calcium in the second trimester of pregnancy.
The study also acknowledged the possibility of a “critical period for neurodevelopment in mid-pregnancy, when vitamin D is required”.
The study concluded that “despite a wide variation in maternal vitamin D concentrations and a high prevalence of low maternal 25-hydroxybitamin D concentrations, maternal vitamin D status was unrelated to the children’s cognitive function”.
Source: Asia Pacific Journal of Clinical Nutrition
“Association between maternal vitamin D status during pregnancy and offspring cognitive function during childhood and adolescence”
Authors: Sargoor R Veena, et al.