At a glance

  • Among vitamin D-deficient infants, up to 95% with clinical rickets are breastfed.
  • Vitamin D is important for general fetal growth, skeletal structure, and tooth-enamel development.
  • Prenatal conditions, geographic location, phenotype, and social and economic environment affect risk of deficiency.
  • While direct infant supplementation is preferred, maternal supplementation has shown promising results.

Rickets, thought to be a disease of the past, is still seen today and threatens to become more of a problem. Documentation of rickets has been seen throughout history. The earliest known medical records describing rickets-like features were seen in the first and second centuries. At the turn of the 19th century, the disease devastated infants and children especially those born in the underprivileged populations of northern industrialized cities in North America and Europe. In research conducted in 1909, autopsy uncovered proof of rickets in 96% of deceased infants aged 18 months or younger.1

In the 1920s, cod-liver oil and sunlight were found to be effective in the treatment and prevention of rickets. It was also discovered that vitamin D was the component in cod-liver oil that led to the protection against rickets. After it was reported in the 1930s that breast milk was not protective against the debilitating disease, cod-liver oil remained the essential method of rickets prevention.

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As the popularity of infant formula rose, cod-liver oil was forgotten, and the incidence of rickets rose again. When the U.S. government decided to universally fortify all formula, milk, and some solid foods sold with vitamin D, rickets retreated once again.

Now that breastfeeding has returned to favor, rickets and vitamin D deficiency have re-emerged in the infant population. This change was first documented in the 1980s and has continued to increase in the United States.2 Some observational reports show that in vitamin D-deficient infants, up to 95% with clinical rickets are breastfed.3

Primary-care providers (PCPs) are ideally suited to educate, encourage, and prescribe vitamin D supplementation. It is important for providers to know which infants are at increased risk and to stay informed regarding the ways to achieve adequate vitamin D sufficiency.

All breastfed infants must reach and maintain adequate vitamin D levels, especially if the infant is at high risk, because the vitamin is a key component of numerous biological processes. This makes vitamin D essential in maximizing health in a rapidly growing infant. Allowing rickets to rise again after knowing the devastation of the disease would be tragic.

Vitamin D in the body

Vitamin D is vital to the establishment and control of the body’s calcium and phosphorus levels. It is fundamental for proper calcium absorption and phosphorus balance. Furthermore, vitamin D is important for general fetal growth, skeletal structure, and tooth-enamel development.

Recent studies have found that vitamin D receptors are spread throughout the body, indicating that the nutrient may play a larger role in cellular well-being and biological processes than previously thought. Data indicate that vitamin D also plays an important role in immune function.4 Preliminary research has linked vitamin D to multiple sclerosis, type 1 diabetes, cancers, respiratory illness, and psychiatric conditions.2,3,5


When assessing levels, 25-hydroxyvitamin D (25[OH]D) is the best indicator because it represents the major circulating form of vitamin D. Measuring the concentration of 1,25(OH)2 instead can lead to errors, because 1,25(OH)2 concentrations will be normal or even elevated in the face of vitamin D deficiency attributable to secondary hyperparathyroidism. Vitamin D deficiency is established as <20 ng/mL in adults. So far, there is no established level for infants and children; however, most providers use the adult standard. Some providers go even further and consider all levels <30 ng/mL to define deficiency in children.

Vitamin D3 supplementation produces more biologically active vitamin D than D2. In 2008, the American Academy of Pediatrics (AAP) returned to the recommendation that infants who are breastfed or who consume less than one liter of formula per day need 400 IU of vitamin D daily to maintain sufficient levels.4,6 Studies concluded that the prior guideline of 200 IU/day did not maintain 25(OH)D concentrations at sufficient levels in infants. In infants receiving 300 to 400 IU of vitamin D per day, 25(OH)D concentrations increased from a mean of 35 nmol/L to 107nmol/L, well over the established norm of 50 nmol/L; 200 IUs did not achieve these levels. Formula-fed infants receive this level of supplementation because the FDA requires formula fortification concentrations to be between 40 and 100 IU/100 kcal.6

PCPs are responsible for educating families, screening infants at high risk, and establishing correct levels of vitamin D in their pediatric patients. Researchers have found that pediatricians are more likely to prescribe or to recommend parents find a way to supplement their infant with vitamin D than are family or general practitioners.