The active form of vitamin D is produced as a byproduct of natural sun exposure; it can also be 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. Low levels of vitamin D have been associated with a spectrum of health problems, and several studies have shown that vitamin D deficiency is also associated with depression.

A recent study indicates that low vitamin D levels may be a risk factor for perinatal depression. In this prospective study, levels of 25(OH)-vitamin D were assessed during pregnancy at 18 weeks gestation from 796 pregnant women in Perth (1989–1992). Depressive symptoms were assessed at 3 days postpartum.

Women in the lowest quartile for 25(OH)-vitamin D levels were more likely to report a higher level of depressive symptoms than women who were in the highest quartile for vitamin D, even after accounting for a range of confounding variables including season of birth, body mass index and sociodemographic factors.
This is the largest study to date to show an association between low levels of vitamin D and perinatal depression. Thus far, the data regarding vitamin D has been somewhat mixed. In a smaller study, Bodnar and colleagues did not find that Vitamin D levels were related to risk of major depression during pregnancy (2011). In another study, however, lower levels of vitamin D were associated with higher Edinburgh Postnatal Depression Scale (EPDS) scores in postpartum women (N=97) (Murphy et al, 2010).

While we do not yet know if supplementing with vitamin D would prevent or treat depressive symptoms in this setting, women who are pregnant or planning to conceive should be screened for vitamin D deficiency. But vitamin D is not just good for mom’s mental health. Several studies have shown that maternal vitamin D status early in pregnancy is associated with risk of low birth weight and small-for-gestational age infants. Other studies have demonstrated that mothers with lower vitamin D levels are at increased risk for gestational diabetes, hypertension, and pre-eclampsia. Also of note is the fact that mothers with low vitamin D status secrete lower levels of vitamin D into the breast milk, putting exclusively nursing infants at risk of deficiency (Haggerty, 2011).

Of late, there has been some controversy regarding the 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. The risk of adverse events increases above 4,000 IU per day.

Both D2 and D3 are effective for raising blood levels of vitamin D, many experts recommend supplementing with vitamin D3, the form that is produced naturally by the body.  However, vitamin D3 supplements are typically derived from cod liver oil or lanolin and are therefore not vegetarian. If an individual has concerns about taking vitamin D3, then vitamin D2 (which is plant-derived) can be an effective replacement.

Ruta Nonacs, MD PhD

Robinson M, Whitehouse AJ, Newnham JP, et al.  Low maternal serum vitamin D during pregnancy and the risk for postpartum depression symptoms.  Arch Womens Ment Health. 2014 Mar 25. [Epub ahead of print]