Pregnancy and Vitamin D for Healthy Babies
Humans can synthesize vitamin D when skin is exposed to strong sunlight. Obviously, babies are dependent upon their mother for vitamin D until birth (in utero). Even after birth, depending upon seasonal temperatures, a baby may be bundled in wraps and kept inside. Thus, the vitamin D status of an infant is totally dependent upon his/her mother.
Zhang and colleagues examined the nutritional requirements for vitamin D in 30 women during pregnancy. The expansion of maternal plasma volume during pregnancy has a dilution effect on blood concentrations of nutrients, especially during the first 10 weeks of pregnancy. Serum 25(OH)D3 concentrations decreased during pregnancy with 63% and 80% of the women have concentrations < 50 nmol/L at 15 and 36 weeks, respectively. Decreases in serum 25(OH)D3 concentrations were observed even during summer months.
Women should avoid low vitamin D status during pregnancy. Low maternal vitamin D status during pregnancy has been associated with low birthweight, poor postnatal growth, bone fragility and increased incidence of autoimmune diseases in children. Harvey and colleagues identified 25,000 studies linking vitamin D supplement use with pregnancy. The report (200 pages long) is summarized here. Bottom line, vitamin D status may be effective in reducing birth-related complications and improving neonatal outcomes.
Vitamin D is not naturally present in many foods. For most good or excellent sources of vitamin D, choose processed and vitamin D fortified products. Although all milk is vitamin D fortified in Canada; not all milk solid in the US is vitamin D fortified. When vitamin D is added to milk, the law limits the amount to 25% of the Daily Value (21CFR104.20) (or 100 IU per serving).
Until the FDA changes the laws to broaden the number of foods/beverages allowed to be fortified with vitamin D, or increases the amount of vitamin D which can be added to processed foods, it is wise to take a vitamin D supplement.
Zhang JY, Horgan R, Kenny LC, Kiely M. Impact of pregnancy on vitamin D status: a longitudinal study. 2014 Br J Nutr doi: 10.1017/S00071145114001883
Mulligan ML, Felton SK, Riek AE, Bernal-Mizrachi C. Implications of vitamin D deficiency in pregnancy and lactation. 2010 Am J Obstet Gynecol doi: 10.1016/j.ajog.2009.09.002
Harvey N, Holroyd C, Ntani G, Javaid M, Cooper P, Moon R, Cole Z, Tinati T, Godfrey K, Dennison E, Bishop N, Baird J, Cooper C. Vitamin D supplementation in pregnancy: a systematic review. Health Technology Assessment. Volume 18. Issue 45. July 2014. DOI: 10.3310/hta18450