Vitamin D is known as the “sunshine” vitamin because of the body’s ability to synthesize it from exposure to sunlight. Along with important benefits for bone, brain, cardiovascular, immune, metabolic, and respiratory health, vitamin D provides critical support for maintaining a healthy pregnancy. However, research finds that 33% of pregnant women in the U.S. are deficient in vitamin D.¹ This means that roughly one in three pregnant Americans (and their babies!) are at risk for pregnancy complications and suboptimal health.^1,2

The risk of vitamin D deficiency is of particular concern for women with a darker skin complexion. This is because high levels of melanin in dark skin absorb the UV rays required for vitamin D synthesis from sun exposure. This article explores how simple preventative measures can help minimize racial health disparities. For more information about Vitamin D, check out “Everything You Need to Know About Vitamin D”.

Rates of vitamin D deficiency are higher for Black and Hispanic Americans

Statistics from a nationally representative sample of American women show that 80% of Black and 45% of Hispanic pregnant women have insufficient levels of vitamin D compared to 13% of White pregnant women.³ (Insufficient vitamin D levels are defined as less than 50 nmol/L or 20 ng/mL in the blood.) More alarming is that at least one other study reports even higher rates of vitamin D deficiency amongst Black (97%), Hispanic (81%), and White (67%) pregnant women.⁴

Despite the variation in numbers, the pattern of disparity between populations is consistent – Black and Hispanic women have higher rates of vitamin D deficiency than White women, with Black women having the highest rates. Consequently, pregnancy complications associated with vitamin D deficiency are also significantly more prevalent in Black and Hispanic women.^5–8 Even more concerning, Black women are four times more likely to die from pregnancy-related complications than White American women (that’s right four times!) and Hispanic American women are nearly twice as likely.⁹

Pregnancy complications associated with vitamin D deficiency

Preeclampsia

This condition affects the blood pressure of pregnant or recently postpartum women and represents one of the leading causes of maternal death. In addition, those who survive this pregnancy complication often deal with other negative health effects, such as an increased risk of cardiovascular, liver, kidney, lung and brain complications.^10–12 As a result, women who’ve experienced this complication are two to eight times more likely to die from cardiovascular disease later in life than women who do not experience it.^10,11

A number of research studies suggest a link between the incidence of this blood pressure complication during pregnancy and vitamin D deficiency.^5,6,13–15 The incidence of this complication in Black women is nearly 60% higher (69.8 cases per 1,000 deliveries) than in White women (43.3 cases per 1,000 deliveries).¹⁶ Similar to the patterns observed with vitamin D deficiency, the rates of this complication are slightly higher for Hispanic women (46.8 cases per 1,000 deliveries) than White women, but not as high as Black women.¹⁶

Other pregnancy complications 

Although not as strong as some of the evidence linking vitamin D deficiency to blood pressure irregularities, other studies implicate an association between low vitamin D status and complications related to blood sugar,^17–21 low birth weight and size,^22–26 and birth prior to “full term”.^{17,24,27–29} The potential consequences of these pregnancy complications are vast and similarly grave, including difficulties related to respiratory, cardiovascular, liver, kidney, lung, intestinal, visual, hearing, neurological and cognitive health.^8,11,26,30

Supplementation can enhance vitamin D status

Dietary sources of vitamin D are generally limited to a few types of fish, egg yolks, fortified cereals, and dairy products. Because the amounts of vitamin D in each source are relatively small, large quantities are needed to get enough vitamin D. For example, egg yolks have just ~20 IU of vitamin D, while fortified breakfast cereals, cheeses and milk contain around 100 IU per serving. Canned mackerel, tuna, salmon and sardines have about 230 – 600 IU per 3.5 oz. Considering these limited dietary sources, food sensitivities and preferences, experts recommend supplementation.

Research consistently shows that vitamin D supplementation can increase maternal vitamin D levels, thus decreasing the incidence of vitamin D-related pregnancy complications. However, the amount of vitamin D found in most prenatal vitamins is not enough to achieve sufficient blood levels for pregnant women, especially Black and Hispanic women who likely need more. Even combining dietary sources of vitamin D with prenatal vitamins during pregnancy is not enough for most women. For example, researchers found that 76% of moms were still deficient when taking a prenatal supplement with 600 IU/day plus two glasses of fortified milk.¹²

However, a study found that supplementing with 4000 IU/day of vitamin D could safely and effectively increase vitamin D to healthy blood levels for Black, Hispanic and White pregnant women.³² Still, it is recommended that pregnant women work with their physician to obtain a vitamin D blood test and discuss their personal dietary supplement requirements. For more information about the role of vitamin D during pregnancy, check out “The Importance of Vitamin D During Pregnancy”and “Three Key Nutrients Your Prenatal Vitamin May be Lacking”.

Vitamin D plays an important role in a healthy pregnancy

Given its important contributions to numerous physiological systems, a deficiency in vitamin D can yield significant health consequences, especially during pregnancy. Because melanin absorbs the UV rays required for vitamin D synthesis, the darker skin pigmentation of many Black and Hispanic Americans puts them at a higher risk of vitamin D deficiency. Since dietary sources of vitamin D are limited, supplementation represents a simple but significant method for decreasing the incidence of vitamin D-related pregnancy complications, which may lead to greater overall health and well-being for women and their babies.