The case was that of a 4-month-old African American infant presenting in the ER with a history of seizures and labs showing low calcium and phosphate, and very elevated parathyroid hormone (PTH). The cause? A lactose intolerant mom who did not take prenatal vitamins consistently. The diagnosis? The metabolic bone disorder Rickets, most commonly associated with vitamin D deficiency.
Pediatric endocrinologist Dominique Long presented the case at Johns Hopkins recent endocrinology conference for primary care clinicians to stress that, yes, vitamin D deficiency is still very much a condition affecting the bones. Without vitamin D, she noted, only 10 to 15 percent of dietary calcium and about 60 percent of phosphorous is absorbed. That’s especially important for children in that 90 percent of adult bone mass is gained in the first two decades of life.
But vitamin D deficiency is no longer just about bones, she added, citing recent research pointing to non-skeletal actions of vitamin D in vitro, and vitamin D receptors showing up throughout the body. In the past few years, numerous studies have shown that optimizing your vitamin D levels may help prevent many cancers, including breast, colon, lung, ovarian, pancreatic, and prostate cancers. However, Long noted, these studies are based on retrospective data and need to be supported by further studies.
Nonetheless, Long said, “The definition of vitamin D deficiency in pediatrics is kind of evolving.”
So, how do you define vitamin D deficiency?
The 25-hydroxy vitamin D test, Long noted, is still considered the most accurate way to measure vitamin D in the body. What’s not so clear is how much vitamin D is optimal? Although the American Academy of Pediatrics (AAP) in 2008 set vitamin D deficiency at 20 nanograms per milliliter (ng/mL), Long noted – and many pediatricians at the conference agreed – that number may be too low.
Who is deficient?
Long cited studies showing that as many as three out of four Americans have suboptimal vitamin D levels. Why are so many people deficient? Long cited greater use of sunscreen, few natural sources of vitamin D in diets, and a lack of vitamin D supplementation in breastfed infants. A 2009 Pediatrics study of over 6,000 children showed that patients were more likely to be deficient if they were older, female, African American, Mexican American, if they consumed milk less than once a week, or watched TV four or more hours per day. In a 2008 infants and toddlers study (Archives of Pediatric Adolescent Medicine 2008;162(6):505-512), 40 percent of patients had vitamin D levels less than 30 ng/mL, which was associated with breast feeding without supplementation and lower milk intake.
“Even if the mom has the most optimal vitamin D levels, there’s still no vitamin D in breast milk,” Long said. “This is why vitamin D supplementation in breast milk is very important for breastfed infants.”
Factors protective against vitamin D deficiency included prenatal vitamin use through the 2nd and 3rd trimesters, though 30 percent of the women who take prenatal vitamins are still deficient. “Even healthy diets,” Long said, “do not contain adequate vitamin D.”
So, what should be the daily recommended intake of vitamin D for children?
According to the AAP, breastfed and partially breastfed infants should be supplemented with 400 international units (IU) per day of vitamin D beginning in the first few days of life. Non-breastfed infants and older children who are ingesting less than 1000 ml/day of vitamin D fortified formula or milk should receive 400 IU each day. Adolescents who do not obtain 400 IU of vitamin D per day in their diet should also receive 400 IU supplement, and higher doses may be needed for children at higher risk of vitamin D deficiency (Pediatrics 2008:122(5): 1142-1152). For example, African American children, who are much more likely to be deficient, need 800 IU daily. Also, because body fat sequesters vitamin D and makes it less bioavailable to the body, Long explained, obese individuals need at least twice the amount of vitamin D supplement.
How should children receive supplements? Vitamin D is available in both prescription and over the counter, though the Food and Drug Administration, Long stressed, does not monitor the latter: “So, we don’t know exactly how much vitamin D is in there.” She added, “In deciding whether to go with prescription or over the counter, you just have to gauge whether your patients will be compliant or not to the regimen you would use.”
For vitamin D deficient children, the Pediatric Endocrine Society recommends 1,000 IU once daily for infants less than 1 month of age, 1,000-5,000 IU for children 1-12 months old, and 5,000 IU for older children. Long recommends 2,000 IU by mouth once daily for almost all ages, or 50,000 IU by mouth once per week for older children or those who will not comply with a daily regimen. Vitamin D levels should be checked at 2 to 3 months to see how the patient is responding. Once the deficiency has been corrected, patients may be prescribed a maintenance dose of between 400 and 1,000 IU by mouth daily or 50,000 IU by mouth every 4-6 weeks. If non-compliance is an issue, Long said, try 50,000 IU once a week for 3 to 8 weeks.
“If the patient is still noncompliant,” Long said, “you may give 100,000 to 600,000 IU over 1 to 5 days, followed by maintenance dosing.”
How are pediatricians responding? In a 2009 study in the AAP’s online journal NeoReviews, 36 percent of pediatricians recommended vitamin D for all breastfed infants, but the rate of vitamin D use was only 15.9 percent.
“We have an important role to educate patients that breast milk is excellent, but it doesn’t have vitamin D,” Long said. “Pediatricians need to supplement with vitamin D.”
Pediatricians need to watch calcium levels, too, Long said. Calcium supplementation increases bone mass in children, she noted, but the effect does not persist once supplementation is discontinued. Low milk intake during childhood is associated with a 2-fold-greater risk of fracture.
“So, we need to ask our patients about calcium,” Long said. “If the patient can’t consume adequate dietary calcium from sources like milk, yogurt, cheese and fortified juice, you may need to add a supplement."