Vitamin D research leads to first-of-its-kind recommendation for pregnant patients

May 04, 2017
close up of Vitamin D pill bottle with headline "New wonder drug?"
MUSC researchers say vitamin D may play an important role in some aspects of pregnancy and a baby's health.

In a bold move, MUSC Health has become the first health care provider in the nation to recommend that pregnant patients who are considered vitamin D-deficient take 4,000 international units, or IU, of vitamin D every day. Neonatologist Carol Wagner called it a quantum leap in clinical practice. "It's already translated into benefits for our pregnant moms," she said.

Longtime Medical University of South Carolina vitamin D researcher Bruce Hollis agreed. "After many years of studying vitamin D in relation to improving birth outcomes, MUSC is the first academic institution to provide pregnant women with 4,000 IU of vitamin D daily, which is almost 10 times higher than the amount currently recommended by the government. We hope this will improve pregnancy outcomes, which the state of South Carolina chronically struggles with."

They point to research suggesting that getting enough vitamin D during pregnancy may help in several key areas, including: 

  • Preventing gestational diabetes
  • Lowering the risk of preeclampsia
  • Reducing the risk of asthma

And it may do much more than that, Wagner said. She's currently studying how vitamin D delivered to babies through breast milk affects their immune systems. She also wants to know just how much vitamin D the mother needs to take to benefit the baby. "We're comparing women who are on 400 international units versus 6,400 international units," Wagner said. "We're looking at differences in their immune system's signature that's given through their milk to see if there really is a difference."

Four hundred international units of vitamin D is the amount most prenatal vitamins contain. Wagner said that's probably not enough – in fact, not even close. Her position is based on previous research at MUSC and elsewhere, including a study of about 350 women conducted by Hollis, Wagner and colleagues. It found 4,000 IU per day for pregnant women was safe and didn't cause any harmful effects.

Meanwhile, MUSC Health obstetrician Roger Newman is looking at vitamin D's possible role in another area that can have a dramatic impact on babies: preterm birth, which can cause lifelong problems. He and his co-workers recently finished part of a field trial testing whether raising pregnant women's vitamin D levels to between 40 and 60 nanograms per milliliter of blood serum would lower the risk of giving birth prematurely. 

"The preliminary results are very encouraging," Newman said. "There was a 65 percent lower risk of preterm birth for whites and 68 percent for non-whites."

Non-whites, who were mainly African-Americans in Newman's study, tend to absorb less vitamin D from the sun because their skin has more melanin. Melanin is a natural sunscreen. 

Across the country, the babies of African-American women are 50 percent more likely to be born prematurely than the babies of white mothers. Newman said his research is not trying to suggest that vitamin D deficiency is the only potential cause - genetics and the environment almost certainly play important roles in causing premature births. But the obstetrician said vitamin D deficiency is well worth looking at, and it's a relatively simple problem to address.

MUSC is far from alone in its interest in exploring the impact of vitamin D on health.

A recent workshop on vitamin D included speakers from Harvard Medical School, the University of North Carolina and the University of Birmingham, England, in addition to researchers from MUSC. 

Martin Hewison, a professor of molecular endocrinology at the University of Birmingham, pointed out that one recent report suggests vitamin D deficiency during pregnancy is a "candidate risk factor" for autism spectrum disorders in children. Other speakers discussed research into whether vitamin D deficiency is linked to everything from low birth weight to babies' tooth enamel.

Hollis said it's time to think even more broadly. He envisions a multi-site study looking at the possible benefits of vitamin D from pre-conception through the toddler years and maybe beyond.

"We'd introduce high-dose supplementation in women who want to get pregnant and follow them for pregnancy for preeclampsia," he said. "Then we'd follow them three to five years after that to look at asthma prevention. There are probably instances of brain development and autism, probably susceptibility to multiple sclerosis."

Hollis said women and children aren't the only ones who may benefit from making sure they have high enough vitamin D levels. He was involved in an influential study at MUSC exploring whether vitamin D could inhibit inflammation in men with prostate cancer. Hollis and colleagues looked at 37 men who were planning to have elective surgery to remove the prostate gland after a diagnosis of low-grade cancer. All had to wait 60 days for their operation to allow inflammation from their biopsies to ease. So during that time, some were given 4,000 international units of vitamin D a day. The others got a placebo. 

Hollis said the men who got vitamin D saw improvements in their prostate tumors while the placebo group's tumors either held steady or got worse. The study was small and not a definite indicator that vitamin D can treat or cure prostate cancer, but it was promising enough to generate a flurry of coverage within the scientific community and beyond.

Vitamin D

So what is vitamin D, and why is it potentially so important? First of all, despite its name, Newman said it's actually not a vitamin. "I see vitamin D more as a hormone." 

The National Institute of Health's Office of Dietary Supplements calls vitamin D a nutrient that's important for good health and strong bones. The body makes vitamin D when it's exposed to direct sunlight. 

Some foods also contain vitamin D, but Wagner said not enough for most of us. "You can’t get it from the diet unless you eat polar bear or lots of fish every day, sort of the traditional Inuit diet. Unless you have that, you have to take a supplement."

Foods rich in vitamin D include:

  • Cod liver oil (1 tablespoon contains 1,360 IU)
  • Swordfish (3 ounces, cooked contains 566 IU)
  • Sockeye salmon (3 ounces cooked contains 447 IU)
  • Tuna fish canned in water and drained (3 ounces contains 154 IU)
  • Fortified milk (1 cup contains 115-124 IU)

There's no dispute about the fact that people need vitamin D to be healthy. The NIHrecommends babies get 400 IU of vitamin D a day. From the age of 1 to 70, the recommendation is 600 IU, and that includes pregnant and breastfeeding women. For people 71 and up, the government recommends 800 IU.

MUSC researchers warn that while that's enough for bone health, it's not enough for other issues, especially those related to pregnancy. 

Newman said there is some concern that too much vitamin D can be harmful. While excessive vitamin D from the sun won't cause toxicity, taking too many supplements can. The National Institutes of Health reports that the threshold for vitamin D toxicity is between 10,000 and 40,000 international units per day. 

The results of taking too much can be serious, including eating disorders, heart arrhythmias and elevated blood levels of calcium that can damage the heart, blood vessels and kidneys. But in high dose supplementation trials performed at MUSC, Newman said none of these complications was identified among pregnant women receiving 4,000 IU per day of vitamin D supplementation.

There's also concern that too many people are taking vitamin D supplements unnecessarily. The New York Times recently ran article called "Why are so many people popping vitamin D?" It pointed out that people are being tested for vitamin D deficiency who don't have any risk factors, such as osteoporosis. It also reported that there's no consensus that vitamin D can fight a host of health concerns from depression to cancer.

Vitamin D supplementation during pregnancy is under scrutiny as well. A 2014 article in the journal Health Technology Assessment looked at 76 studies and found that while there was "modest evidence" showing having enough vitamin D affected the baby's birth weight, bone mass and serum calcium concentrations, more research was needed. And the American Congress of Obstetricians and Gynecologists has said there's not enough evidence to warrant screening all pregnant women for vitamin D deficiency.

The MUSC researchers agree that more study is needed. That drives their ongoing work. But they also say it's important to act now and give vitamin D-deficient pregnant women supplements, which  have the potential to impact them and their babies in multiple ways. They're relatively inexpensive, and unless a woman takes too many, research shows they are not harmful.  

"We live on the edge of deficiency," Wagner said. "Vitamin D is not the ogre."