Vitamin D deficiency has turned into a public health concern in recent years in the United States. With more people likely experiencing vitamin D deficiency or insufficiency due to declining milk intake, increased UV-protective sunscreens, and decreased sun exposure. This is of particular concern for women who are of childbearing age, since many nutrient deficiencies during pregnancy are often associated with adverse outcomes for the mother and the developing fetus.
Vitamin D, which is known as calcitriol in its active form, is vital for calcium homeostasis and a variety of vitamin D dependent gene transcription in humans. Vitamin D deficiency during pregnancy has been linked with altered bone development and rickets (1). In addition, recent findings suggest that vitamin D deficiency could also be associated with asthma and type 1 diabetes (1).
Recent research has investigated the effects of vitamin D supplementation, particularly during pregnancy. However, there still no clear recommendation for vitamin D intake during pregnancy. The current recommended DRI of vitamin D for pregnant women is an adequate intake (AI) of 15 µg/day (400 IU), with an tolerable upper intake level (UL) of 100 µg/day (4000 IU) (2). It is estimated that as high as 41.6% in U.S. adults are vitamin D deficient or insufficient, prompting many to suggest supplementation interventions (3).
There is a greater body of evidence that demonstrates the effects of vitamin D deficiency or insufficiency during pregnancy, yet there is still less known about the consequences of higher vitamin D intake due supplementation. The purpose of this paper is to determine if high dose vitamin D supplementation increases the risk for adverse maternal or fetal outcomes.
The following methods were used to retrieve the studies that were used in the analysis of the effects of high dose vitamin D supplementation on pregnancy outcomes in humans.
The author conducted a search on PubMed via UC Davis access portal. The following sets key words were used for the search of articles:
(vitamin d); AND
The search was also filtered studies that have been published in the past 5 years and free full texts available. The literature search resulted in 11 results.
The results were then screened based on the following inclusion and exclusion criterion:
The inclusion criteria for studies in this analysis were publication in the English language, supplemented vitamin D at higher levels than the 5µg or equivalent, measured vitamin D status, conducted on pregnant women, and measured a maternal or infant pregnancy outcome (i.e. birth weight, gestational diabetes, preeclampsia, type 1 diabetes, asthma) (Figure 1). Studies that included women with preexisting the following conditions: hypocalcaemia, hyperthyroidism, or HIV were excluded.
Of the 11 results screened that met the full inclusion criteria, only 3 were randomized controlled trials that met all the...