Vitamin D status in breastfed term babies

Abstract

Vitamin D is the essential precursor of 1,25,-dihydroxyvitamin D, the steroid hormone required for calcium absorption, bone development and growth in children. Whatever the source of vitamin D, it is then converted sequentially to 25-hydroxyvitamin D in the liver and 1,25dihydroxyvitamin D (the active hormone) in the kidney. In pregnant and lactating women, vitamin D stores are built by exposure to sunlight and from dietary sources. Their vitamin D status does not change significantly during pregnancy or lactation (1). Newborns at birth depend on their mothers for vitamin D. While cord serum 25-hydroxyvitamin D is significantly lower than that observed in maternal serum, it is directly correlated to it, thus implying transfer across the placental barrier (2). Adverse effects of maternal vitamin D deficiency on the foetus include possible delayed growth, delayed bone ossification and abnormal enamel formation, as well as alterations in calcium homeostasis during the neonatal period (2).Determining the amount of vitamin D provided by the sun or food is difficult. The most precise information is given by serum 25-hydroxyvitamin D levels, considered to be a direct reflection of the body vitamin D stores. Vitamin D deficiency is generally considered to be associated with a serum 25-hydroxyvitamin D concentration under 40 nmol/l, and a level below 25 nmol/l corresponds to osteomalacia and/or rickets.In this issue of Acta Paediatrica, Atiq and colleagues (3) report a prospective study performed in breastfed infants and their nursing mothers. In this Pakistani population, the authors identified a high incidence of vitamin D deficiency (below 25 nmol/l) in mothers (45%) and also in their infants (55%). The socioeconomic class was identified to be one of the most important factors associated with vitamin D deficiency. The authors also pointed out that this factor was mainly due to the lower sunshine exposure in infants and that the infants from the upper class have a higher risk of vitamin D deficiency because their mothers tended to confine them indoors.It has been demonstrated that infants fed exclusively with human milk are at risk for vitamin D deficiency (4, 5). During the first 6-8 weeks of life, the vitamin D status of infants is dependent on their vitamin D status at birth (i.e. the vitamin D status of the mother), their vitamin D intake and on their exposure to light. Longitudinal measurement of vitamin D metabolites in the serum of exclusively breastfed infants (not receiving vitamin D supplementation) who were born to vitamin D replete mothers suggested that a depletion of vitamin D stores occurs within 8 weeks after delivery in the majority of the infants (6). Human milk 25-hydroxyvitamin D concentrations correlate with maternal serum 25-hydroxyvitamin D levels (7). This correlation would predict that the mother's vitamin D status should play a role in determining the vitamin D status of her infant but this does not appear to be the case. A significant increase of the 25-hydroxyvitamin D concentration in human ...

Vitamin D deficiency and supplementation during pregnancy

“…Previous supplementation studies suggest a 25‐hydroxyvitamin D level below 50 nmol/l is insufficient for bone health in adults and children 20–23 . We define 25‐(OH) D sufficiency as levels ≥ 50 nmol/l, insufficiency as levels 25–50 nmol/l and deficiency as levels < 25 nmol/l 24 .…”

“…Previous supplementation studies suggest a 25-hydroxyvitamin D level below 50 nmol/l is insufficient for bone health in adults and children. [20][21][22][23] We define 25-(OH) D sufficiency as levels ≥ 50 nmol/l, insufficiency as levels 25-50 nmol/l and deficiency as levels < 25 nmol/l. 24 Small for gestational age was defined as birth weight less than the 10th percentile after adjustments for gestation at delivery, infant sex, maternal ethnicity, parity, height and weight.…”

Implications of vitamin D deficiency in pregnancy and lactation

“…In contrast, babies who are exclusively breastfed are at higher risk for vitamin D deficiency. 86 Human milk contains a very low concentration of vitamin D (approximately 20–60 IU/L), which represents 1.5–3% of the maternal level. 87 This concentration is not sufficient to maintain an optimal vitamin D level in the baby if exposure to sunlight is limited.…”

Vitamin D in pregnancy: A metabolic outlook

“…Fetal Vitamin D concentrations are mainly dependent on maternal concentration, and maternal deficiency may lead to adverse outcomes in offspring. Vitamin D-deficiency in mothers have significantly increased risk of infantile rickets due to inadequate maternal–fetal transfer of 25-hydroxyvitamin D.[32] Recent retrospective studies found a significant and previously undetected association of maternal vitamin D deficiency with rickets-associated infant heart failure and with acute lower respiratory tract infection,[33] a serious complication often associated with sepsis without clinical signs of rickets. While vitamin D supplementation in pregnancy has previously been associated with reduced risk of wheezing and type 1 diabetes.…”