After giving birth to her son last year, Sarah Mann, a mother in Santa Barbara, Calif, became one of an increasing number of women in the United States choosing to breastfeed her children.
"It seemed natural to me," Mann, 29, said. "The main thing is that it's good for him — that was my greatest motivation."
But what Mann didn't know was breast milk — considered the best source of nutrition for babies — is low in vitamin D. The American Academy of Pediatrics (AAP) recommends all children, including infants, get 400 international units (IU) of vitamin D per day, an amount that is not possible to get from breast milk alone, experts say. And while people can also get vitamin D from sunlight, the AAP advises that infants younger than six months avoid exposure to direct sunlight due to skin cancer risk.
So what's a mom to do?
The AAP recommends vitamin D supplements, in the form of drops, be given to breastfed babies shortly after birth. However, Mann's pediatrician never brought this up, and she didn't come across it in any of the materials she, as a new mom, voraciously read. "I didn’t even know that that was something we should be doing," she said.
Mann is not alone. Only about 5 percent to 13 percent of breastfed babies received vitamin D supplements between 2005 and 2007, according to a study published in April in the journal Pediatrics. These low numbers might stem from the misperception that breast milk contains everything the baby needs, experts say.
"I think that the perception that 'breast is best' leaves people just giving the breast milk and thinking that there isn’t anything else that the breast milk might be missing," said Dr. Joyce Lee, a pediatric endocrinologist at the University of Michigan.
And recent surveys indicate less than half of pediatricians are recommending vitamin D supplements to breastfed babies, another possible reason for the low numbers. Experts hope to get the message out, to both mothers and pediatricians, in regards to the importance of vitamin D for children.
What does vitamin D do?
Vitamin D helps the body absorb calcium and phosphorus from food, and is important for bone development. Children who are severely deficient in vitamin D can develop rickets, a disorder in which the bones weaken which can lead to fractures and skeletal deformities.
There's also emerging evidence that vitamin D provides a host of other health benefits for kids, including boosting immunity and helping to prevent diabetes and cancer later in life(although additional research needs to be done to confirm this). [Related: 9 Good Sources of Vitamin D]
Prior to 2008, the AAP recommended children and infants older than two months receive 200 IU's of vitamin D per day — half of the current recommendation, but still, an amount that required supplements for breastfed babies. Under the old recommendation, cases of rickets were still showing up, and studies had found that many children are not getting enough vitamin D. So the AAP decided to double its recommendations.
"If you can pick up a kid who doesn’t have signs of rickets yet, but has low vitamin D, then you say 'okay, that’s the child I need to treat because I don’t want them to develop rickets,'" Lee said.
Less is known about what might happen to children who are not getting the recommended amount of vitamin D, but who don't yet show symptoms of a deficiency. One consequence might be an increased risk for osteoporosis later in life, said Dr. Jatinder Bhatia, the chair of the AAP Committee on Nutrition and a pediatrician at the Medical College of Georgia. He noted that infancy is one period in life when the body has an intense need for the materials to build bone.
Why aren't women supplementing?
It may be that some breastfeeding mothers, like Mann, aren't giving supplements to their children because their pediatricians aren't recommending it.
A study published in the January issue of Pediatrics found, of pediatricians who responded to a survey between 2006 and 2008, just 36.4 percent recommended vitamin D supplements to breastfed infants in accordance with the AAP's recommendation.
In some instances, pediatricians might be hesitant to recommend supplements because they don't want to do anything that would deter mothers from breastfeeding.
"We really want parents to breastfeed, and if we're saying the breast milk really isn't complete, that you need something extra, then that might be an inhibition to breastfeeding," said Dr. Kenneth Feldman, a pediatrician at Seattle Children's Hospital, who conducted the Pediatrics study. "So those folks who place a greater importance on having the breastfeeding itself…might elect not to do anything that would dissuade families from breastfeeding."
However, some breastfeeding mothers see this concern as unwarranted.
"In my experience, mothers who breastfeed know that it is better for their children, which is why they do it. I don't think needing to add a supplement would change that, as it is still best for baby," Mann said. In her experience, women usually stop breastfeeding due to physiological problems with the process, such as not producing enough milk, and issues with going back to work.
"Might a mom use the vitamin D issue as a reason for stopping? I doubt it, and only if she were already considering it anyway," she said.
Feldman said he suspects that if he and his colleagues conducted the study again today, they would find a higher percentage of pediatricians recommending the supplements, because of growing awareness about the prevalence of vitamin D deficiency in children. But he said there is still skepticism about what the optimal levels really are, which may lead some pediatricians to think that low vitamin D levels aren't a problem for their patients.
It may also take a while for the pediatric community to catch up with the AAP's recommendations.
"Not all the pediatricians, that I'm aware of, are prescribing this routinely," AAP's Bhatia said. "So that is a gap between the recommendations of the academy and the practicing physicians that needs to be closed," he said.
What about formula-fed babies?
Some women chose not to breastfeed, sometimes due to time constraints imposed by their jobs, or issues with having other children to take care of. And sometimes babies can refuse breastfeeding. In some of these cases, babies are given formula.
Formula is fortified with vitamin D, and historically, formula-fed babies have not been thought to need supplements. But to meet the new AAP recommendations, babies would have to drink about a liter of formula per day, said Cria Perrine, an epidemiologist at the Centers for Disease Control and Prevention.
Perrine recently conducted a study looking at the number of infants who meet AAP's new requirement. While most infants were consuming enough formula to meet the old requirements (200 IU per day), only about one-third drank enough to meet the new requirements, she said.
"We can no longer assume that formula is enough to cover the vitamin D requirements for infants consuming formula," she said. The amount of formula an infant consumes will also vary depending on how old they are and how much solid food they are eating.
As of now, the AAP has not specifically recommended formula-fed infants be given supplements.
What can be done?
Besides public health campaigns, one source of change can come from pediatricians themselves, according to Feldman.
"One of the biggest factors in getting families to actually give their infants vitamin D was the pediatrician's recommendation," he said, referring to a finding in his study. "If we really want breastfed infants to be on supplements, then the pediatricians should be stepping in."
Indeed, Mann said she probably would probably have given her son vitamin D supplements if her pediatrician had recommended them. "Hopefully, nothing bad will come of it," she said.
Her son turns 1 year old today (Nov. 7), and is healthy so far, she said.
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.