CNN — Most new moms aim to breast-feed their babies - a practice encouraged by experts who tout the many health benefits of breast milk.
But breast milk is not perfect when it comes to vitamin D. A new study published Tuesday in a special edition of the Journal of the American Medical Association focusing on child health reiterates that breast-fed babies also need a vitamin D supplement.
The current recommendations to give babies being fully or partially breast-fed 400 IU, or International Units, of vitamin D each day "is quite satisfactory," said lead study author and registered dietitian Hope Weiler of McGill University in Canada.
In 2011, the Institute of Medicine also recommended 400 IU of vitamin D as being beneficial to infants, from newborns to babies up to 12 months - or even beyond.
But most babies who are breast-fed do not receive enough, because most new parents aren't giving their babies vitamin D supplements, according to Dr. Steven Abrams, a professor of pediatrics at Baylor College of Medicine and author of an accompanying editorial published in JAMA.
Abrams, who is also a member of the nutrition committee of the American Academy of Pediatrics (AAP), says only about 10 to 20% of babies who are breast-fed are also given vitamin D.
"We know very well if you don't have enough vitamin D, you can develop rickets as an infant or young child," Weiler said at a news conference on Tuesday. Rickets is a disorder which leads to softening and weakening of the bones.
Vitamin D is essential for growing healthy bones because it helps the body absorb calcium - without enough calcium, bone production may suffer.
Our bodies have the ability to produce vitamin D when our skin is directly exposed to the sun. However, you can't be wearing sunscreen to make this happen and babies younger than 6 months shouldn't be in the sun anyway - according to the AAP and FDA, 6 months is the earliest sunscreen should be applied to babies.
Babies who are exclusively breast-fed or even partially breast-fed are unlikely to get enough vitamin D because their mothers may lack it. Babies who are formula-fed usually receive enough vitamin D because the government requires that it be included in formula.
"A daily exposure of vitamin D intake of 400 IU per day has been demonstrated for almost 100 years to reliably prevent rickets in infants regardless of sunshine exposure or race," writes Abrams in the editorial.
Back in the 1920s, when the recommendations were first established, vitamin D supplements came in the form of a teaspoon of cod liver oil. These days, you can buy a bottle of the supplement and give your baby the recommended amount with an eye dropper.
It's hard to quantify how many babies get rickets because reporting is not required in the United States, but pediatricians like Abrams say they are seeing more cases: "'There's been a mini-epidemic of rickets in the U.S.," he says.
There doesn't appear to be strong pediatrician support for the recommendations, he says, and new parents may not be aware of the recommendation. In addition, families on a tight budget may need to be convinced that buying an over-the-counter vitamin D supplement is important.
A quick survey of some national pharmacy and retail chains shows a bottle of vitamin D drops for infants costs about $9 to $12. That could be a hardship for families on public assistance, which is why Abrams has suggested over the years that it may be worth making these supplements part of public assistance.