The active form of vitamin D is produced by the human body as a byproduct of natural sun exposure; it is also found in certain foods, including some kinds of fish, egg yolks, and fortified dairy and grain products. Certain people – those with decreased sun exposure or diets with low vitamin D – may be more vulnerable to vitamin D deficiency. Vitamin D deficiency is more common than ever, and many experts are concerned that vitamin D deficiency may lead to a wide variety of health problem.
Severe vitamin D deficiency cause rickets; however, the signs and symptoms of vitamin D deficiency are generally not observed in cases of mild deficiency. In fact, most people with vitamin D deficiency are unaware they have this problem.
According to data presented at the European Congress of Endocrinology 2016, vitamin D deficiency in early pregnancy was associated with an increased risk of behavioral issues in preschool children. This information came from the Rhea study in Greece, a longitudinal, prospective pregnancy cohort study designed to evaluate the effects of nutritional, environmental, biological, and psychosocial exposures during pregnancy in 1300 mothers and their children.
This analysis included a total of 471 mother-child pairs. Maternal vitamin D status was measured at 13 weeks of gestation and rated as sufficient (> 75 nmol/L), insufficient (52.5–72.5 nmol/L), or deficient (< 50 nmol/L).
At 4 years of age, the children were evaluated using the McCarthy Scales of Children’s Abilities (MSCA) and their emotional and behavioral development assessed using the Strengths and Difficulties Questionnaire (SDQ) and the Attention Deficit Hyperactivity Disorder (ADHD) Test.
Maternal vitamin D levels lower than 50 nmol/L during pregnancy were associated with increased behavioral problems and ADHD-like symptoms among the offspring.
This is well-done study; however, it must be replicated in other populations and other confounding variables, including the mother’s psychiatric history, must be taken into consideration. Animal studies have shown the vitamin D is important to the development of the fetal brain; however, human studies evaluating the role of vitamin D in neurodevelopment are sparse. Although we clearly need more information on the importance of vitamin D in this setting, making sure that pregnant women are getting adequate levels of vitamin D seems like a relatively benign intervention.
Of late, there has been some controversy regarding what constitutes an adequate dosage of vitamin D. The Institute of Medicine committee has published recommendations for various age groups, reflecting scientific evidence for the health benefits of vitamin D. For adults (70 and younger), the recommended daily allowance is 600 IU/day. Most prenatal vitamins contain 400 IU of vitamin D. Interestingly several recent studies showing the benefits of vitamin D in pregnancy used doses of 4,000 IU per day; however, most health groups recommend taking no more than 2,000 IU of the vitamin in supplement per day.
Ruta Nonacs, MD PhD