SAN FRANCISCO – Vitamin D deficiency is common among children and adolescents, particularly those with chronic disease, Catherine Gordon, MD, said at the annual meeting of the American Academy of Pediatrics.
Yet the precise definition of vitamin D deficiency and the healthy threshold for vitamin D levels lack universally agreed-upon standards. Generally speaking, levels of at least 30 ng/mL (75 nmol/L) appear safe and reasonable for children with chronic disease, and additional research is confirming whether this range is appropriate for other pediatric groups as well. Although too much vitamin D can lead to hypercalcemia, vitamin D intoxication is very rare, said Dr. Gordon, director of the division of adolescents and transition medicine at the University of Cincinnati.
Severe vitamin D deficiency can lead to rickets, when bones have insufficient calcium and phosphorus levels, resulting in bone softening and weakening before growth plates close. If not treated with vitamin D and calcium supplementation, rickets becomes osteomalacia after the growth plates close.
Vitamin D deficiency rates vary by population
It’s difficult to pin down rates of vitamin D deficiency. One 2004 study of just over 300 children found nearly a quarter of them (24%) were deficient based on a threshold of levels below 15 ng/mL, and another 42% had insufficient levels, defined as 20 ng/mL or lower, but all were asymptomatic. Another 2008 study using different cut-offs found that 12% of healthy 8- to 24-month-olds were deficient, defined as levels below 20 ng/mL. Forty percent of the children had suboptimal levels below 30 ng/mL. Overall, a third of the children showed demineralization on their x-rays. While the season of the year and race/ethnicity did not emerge as predictors of vitamin D insufficiency, breastfeeding without supplementation and lack of milk consumption did.
Because the vitamin D content in human breast milk is low, breastfed infants typically develop low vitamin D levels unless they receive supplementation or plenty of exposure to sunlight. A maternal dose of 6,400 IU of vitamin D is needed for breastfed infants to reach normal vitamin D levels, Dr. Gordon said. Babies born to mothers with vitamin D deficiency have the highest risk of becoming deficient themselves, although formula-fed babies usually receive plenty through the vitamin D fortification in infant formula.
Among adolescents, obesity remains a common risk factor, and those with obesity require higher doses to correct deficiency or insufficiency. A study in the Journal of Pediatrics this year found that adult-sized teens need at least 5,000 IU of vitamin D3 a day for 8 weeks to correct deficiency. Similarly, a small 2012 study of 61 children and adolescents with inflammatory bowel disease found that supplementation of 2,000 IU of vitamin D3 daily or 50,000 IU of D2 weekly, for 6 weeks, more effectively corrected vitamin D deficiency than 2,000 IU daily of vitamin D2 without any changes to parathyroid hormone suppression.
How much to supplement
Much debate and uncertainty surround how much (if at all) healthy infants, children, and adolescents should be supplemented with vitamin D. The American Academy of Pediatricssupplementation of 400 IU of vitamin D from birth through adolescence for all children and teens, although that’s far below the safe upper limit of vitamin D intake, Dr. Gordon said.
The health and sciences division (formerly the Institute of Medicine) of the National Academies of Sciences, Engineering, and Medicine, by contrast, recommends a daily intake of 400 IU of vitamin D for the first year of life and then 600 IU for age 1 through old age. The safe upper limits set by the health and sciences division include 1,000 IU for infants up to 6 months old, 1,500 IU for infants aged 6 months to 1 year, 2,500 IU for toddlers up to 3 years, 3,000 IU for children aged 4-8 years, and 4,000 IU for those 9 years and older.
Yet the Endocrine Society recommends a greater amount of supplementation for children at risk for vitamin D deficiency or low bone density mass: from 400 to 1,000 IU for children 1 year and younger, and 600-1,000 IU for all older children, adolescents, and adults. The Endocrine Society also cites a higher safe upper limit of 2,000 IU for infants up to 12 months and 4,000 IU for those aged 1 year and up.
Part of the discordance in these recommendations lies in what populations they are aimed at, Dr. Gordon explained. While the health and sciences division recommendations were written for healthy children and adolescents, the Endocrine Society is specifically addressing those in risk groups, such as transplant recipients, those with chronic conditions that can cause malabsorption, and those taking anticonvulsants or receiving other treatments that can threaten bone health. Among older children and adolescents, anorexia nervosa is also a risk factor for inadequate vitamin D levels.
Dr. Gordon recommended 600 IU of vitamin D daily for all healthy children and teens while noting that those in risk groups may require 1,000-2,000 IU to prevent vitamin D deficiency.
Additional concerns with inadequate vitamin D
Aside from bone mineral density and levels of 25(OH)D (25-hydroxy vitamin D) and parathyroid hormone, vitamin D insufficiency may be suspected based on several other biomarkers, including fractures or falls, intestinal calcium absorption, dental health, insulin sensitivity, beta-cell or immune functioning, respiratory disease such as wheezing or tuberculosis, and possibly hypertension.
Researchers have developed new interest in exploring whether factors during childhood and adolescence – critical years for bone acquisition – such as vitamin D levels might influence the risk for osteoporosis later in life, Dr. Gordon said.
Both males and females reach their peak bone mass and skeletal strength in their early to mid-20s and maintain these through about their mid-40s. While individuals have no control over intrinsic factors that help determine their bone mass, such as sex, family history, and ethnicity, other extrinsic factors are also bone mass determinants, including diet, body mass, a particular individual’s hormonal mix, illnesses and their treatments, physical activity level, and lifestyle choices.
Therefore, health providers should encourage patients to regularly exercise, maintain a healthy weight, eat healthfully, and take daily supplements, Dr. Gordon said. She only recommended testing 25(OH)D levels in those at risk for deficiency and/or low bone mass.
Dr. Gordon reported no relevant financial disclosures.