Dr. Sina Gallo and her team of researchers analyzed data from a study collected by the Supplemental Nutrition Program for Women, Infants, and Children (WIC).
They found two out of three infants enrolled in the program weren't getting enough vitamin D.
"And so, this will affect their bones, the development of their bones," said Dr. Gallo.
Doctors say vitamin D deficiency in infants and children can lead to nutritional rickets, potentially causing bone fractures and stunted growth. It can also play a role in diseases like multiple sclerosis and type 1 diabetes as adults.
"What I worry about is that we are limiting the ability to optimize an infant's health very early on in life," said Dr. Gallo.
Experts recommend infants receive 10 micrograms of vitamin D per day. Of the 2,300 infants enrolled in the study, Dr. Gallo says only 7% of those breastfed were hitting the daily recommended target without supplementation. For mothers who need to supplement, there are various products available over the counter.
"There's some oil-based that offer a tiny amount of the supplement of that you would give directly to the infant," said Dr. Gallo.
But for low-income families on WIC, the federal program doesn't cover the supplemental vitamin D drops.
"That is a group that we thought was most vulnerable," said Dr. Gallo.
And while there is currently still a nationwide formula shortage due to a massive formula recall and supply chain issues, Dr. Gallo says for moms who can't breastfeed or choose not to, formula is a good option.
"It is, in terms of nutrition, it contains all the vitamins and minerals including Vitamin D, which is fortified in formula. So, it is nutritionally adequate," said Dr. Gallo.
Dr. Gallo's team conducted a similar study in Canada and found about 75% of infants were getting enough vitamin D supplementation. Compare that to less than 30% of infants in the U.S. meeting the recommendation.
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