The Journal of Nutrition
Vitamin D Deficiency in Pregnancy:
Bringing the Issues to Light
Marjorie L. McCullough*
Epidemiology and Surveillance Research, American Cancer Society, Atlanta, GA 30329
See related article: J Nutr. 137-2: 447–52, 2007.
compelling evidence that 1) pregnant women and their neonates
living in the northern U.S. are at risk of vitamin D deficiency, 2)
contributes little to vitamin D status among black women and
their neonates, and 4) current formulations of prenatal vitamin
supplements may be inadequate to achieve desired serum 25
hydroxy vitamin D [25(OH) D] (storage form of vitamin D)
concentrations. The authors analyzed a random subsample of
banked maternal and cord serum from 200 white and 200 black
participants in the Pregnancy Exposures and Pre-eclampsia
Prevention Study, conducted through Pittsburgh clinics. Early
mothers) were classified as vitamin D deficient, and insufficiency
wascommon amongwomenofbothracialandethnic groups. By
slightly. The prevalence of vitamin D deficiency for neonates was
even greater than that of their mothers. This is particularly
prenatal vitamins by the end of the study period.
Why is this study timely? First, rickets has reemerged in the
U.S., particularly among black infants (2). Maternal vitamin D
insufficiency was also recently associated with reduced bone
mineral accrual in offspring followed for 9 y (3). But apart from
vitamin D?s well-established role in maintaining proper bone
mineralization, vitamin D insufficiency has also been associated
in some studies with a host of other health outcomes, including
Several of these outcomes are linked to early life exposures, and
many are more common among black individuals. Ironically,
while evidence supporting the many health benefits of vitamin
D grows exponentially, evidence is also building that vitamin D
deficiency is a common public health problem (6,7). Those most
atriskinclude darkly pigmented individuals(inwhomcutaneous
vitamin D synthesis is blunted), the elderly, those who, for med-
ical or cultural reasons, avoid sun exposure, and solely breast-fed
This study addressed 2 probable causes of vitamin D
insufficiency in this population: inadequate skin synthesis and
supplementation. Vitamin D is found naturally in few foods
(e.g., fatty fish), so major dietary sources include fortified foods
(primarily milk and some ready-to-eat cereals in the U.S.) and
vitamin supplements. However, sun exposure is the most
important source, except in the winter among people living at
$37? latitude, when UVB rays do not reach the earth surface
and cannot form vitamin D precursors in the skin. The authors
of this study observed disparate changes in serum 25(OH) D
levels between white and black women from winter to summer
months: in white women, 25(OH) D levels rose in the summer
(although still not enough to eliminate insufficiency), but in
black women and their neonates, negligible increases in
25(OH) D levels were observed during warmer months.
Although differences in efficiency of cutaneous vitamin D
synthesis by race or ethnicity are well-known (6), this study is
among the largest to examine these questions in this at-risk
population. Information on specific sun exposure practices in
both groups would have been informative, but was unavail-
able, presumably because this was not the primary hypothesis
of the parent study.
Perhaps more remarkable was that, by the end of the
pregnancy, 90% of all women were taking prenatal vitamins,
and yet deficiency was still common. From the study, it is not
clear how diligently the women were taking prenatal vitamins
(insofar as the regular use of prenatal vitamins was defined as
‘‘at least once per week’’) or whether supplement-use patterns
varied by race or ethnicity. A subanalysis of 25(OH) D levels
among daily users would have helped clarify the efficacy of
prenatal vitamins, which, although they contain 400 interna-
tional units (IU) of vitamin D, twice the Dietary Reference
Intake (DRI) (8) for pregnancy and lactation, may not contain
enough vitamin D to raise levels sufficiently (2). Another
unknown variable is the form of vitamin D ingested by these
women: both ergocalciferol (vitamin D-2) and cholecalciferol
(vitamin D-3) are found in vitamin supplements, but D-3 is
believed to more effectively raise 25(OH) D. In a national
survey, black women of reproductive age who consumed
‘‘adequate’’ vitamin D intakes (200 IU) from diet and supple-
ments still had a high prevalence of low 25(OH) D blood
concentrations (7). Moreover, NHANES data show that only
half of teenage girls and women consume 200 IU of vitamin D
daily (from food and supplements), and the percentages are
lower among black women (9). Fortified milk is the largest
source of dietary vitamin D in the U.S., but intakes are lower
among blacks, presumably due to greater occurrence of lactose
* E-mail: email@example.com.
0022-3166/07 $8.00 ª 2007 American Society for Nutrition. J. Nutr. 137: 305–306, 2007.
Manuscript received 17 November 2006. Revision accepted 22 November 2006.
by guest on June 5, 2013
Considering these findings, why not raise the DRI for vitamin
D? Most experts agree that the current DRI of 200–600 IU (8) is
too low, and that, based on current evidence, daily requirements
may be closer to 1000 IU (4) or higher (2). Recent reviews and
consensus panels on vitamin D and health also conclude that
more research is needed on optimal vitamin D doses and blood
concentrations for several health outcomes, and on the safety
of long-term higher-dose vitamin D supplementation in all
populations (2,4,10). However, as noted recently, the official
Upper Tolerable Level (UL) of 2000 IU/d makes it difficult to
study the efficacy and safety of higher levels (11), and perhaps
creates a fear of recommending higher doses. Vitamin D toxicity
can occur at much higher intake levels (11) but is rare. De-
veloping expert recommendations is a complex task, because
vitamin D needs vary depending on sun exposure (season,
latitude, skin pigmentation, and sun exposure practices). Con-
sideration of sun exposure as a source requires weighing the
benefits with the risks of UV exposure on the development of
melanoma and cataracts (12). To minimize health risks from
UV exposure and maximize vitamin D status, a balanced diet,
supplementation, and limited amounts of sun exposure are the
preferred methods for obtaining vitamin D (10,13). Momentum
is building for an updated review of the DRI by the Institute of
Medicine. Such an authoritative review would shed light on the
gaps in research and practice and provide needed guidance to
professionals, health organizations, food manufacturers, and the
public, in order to move research forward and improve public
The study in this issue illuminates the danger of assuming
that prenatal vitamins in their present form are ensuring vitamin
D sufficiency in pregnant women and their newborns. Whereas
more studies are needed to determine precise vitamin D
requirements in all populations, we do have enough evidence
to show that current practices are not serving at-risk groups.
Because pregnant women are already under medical care and
taking a prenatal vitamin, the benefits of a higher dose of
vitamin D supplementation and perhaps 25(OH) D screening (in
high-risk groups) is worthy of further investigation.
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