As study after study shows the fundamental role vitamin D plays in disease and health, vitamin D deficiency -- which often develops insidiously in childhood -- should be on every parent's and pediatrician's radar, say physicians from the Johns Hopkins Children's Center.
"Vitamin D deficiency can be a problem year round, but because sun exposure is critical for vitamin D synthesis and production, the winter months further exacerbate what is a perennial problem," says Johns Hopkins Children's Center endocrinologist Dominique Long, M.D.
Levels at or below 20 nanograms per milliliter are considered suboptimal. Levels below 15 constitute deficiency and should be treated with supplements.
Hopkins experts say pediatricians should screen all children for risk factors and order blood tests for those found to be at high risk. Children at risk for vitamin D deficiency include:
- those with vitamin D-poor diets
- breast-fed infants because breast milk contains minimal vitamin D
- obese children
- those with darker skin because darker skin synthesizes less vitamin D from sun exposure than lighter skin
- those with certain medical conditions, including cystic fibrosis, type 1 and type 2 diabetes and certain gastrointestinal disorders, such as inflammatory bowel disease, which can interfere with food absorption
- Several large-scale studies have found that vitamin D deficiency is widespread -- one in 10 U.S. children are estimated to be deficient -- and that 60 percent of children may have suboptimal levels of vitamin D.
Prolonged and untreated vitamin D deficiency can affect multiple organs and functions, including bone growth and density, metabolism, heart and immunity, but it rarely causes overt symptoms and often goes unnoticed.
Vitamin D deficiency in childhood can cause skeletal deformities, brittle bones, frequent fractures and lead to premature osteoporosis in later life. However emerging evidence suggests that vitamin D is involved in far more than bone health. Recent studies have found a link between low vitamin D levels and some cancers, heart disease, suppressed immunity and even premature death. These studies do not show that vitamin D deficiency can cause cancer or heart disease, experts caution, but do suggest that vitamin D may be a powerful player in the genesis of such disorders.
Much of our life-long health is pre-programmed in childhood, and many adult diseases are rooted in exposures, lifestyle and diet during the first decade of life, experts say, and vitamin D, or lack of it, is a classic example.
Long says that she sees at least one toddler with rickets-induced bowing of the legs in her clinic every month and at least one patient per year with seizures stemming from low calcium levels. Without sufficient vitamin D, only 15 percent of the dietary calcium is absorbed, and low calcium can, in rare cases, cause seizures and heart-rhythm anomalies, Long says. Other symptoms of low calcium include poor muscle tone, insufficient dental enamel and muscle spasms.
The good news is that once detected, vitamin D deficiency can be usually corrected easily with high-dose supplementation, Long says. To prevent vitamin D deficiency, the American Academy of Pediatrics recommends that all breastfed infants receive supplemental 400 IU daily until they are weaned and start consuming vitamin D-fortified formula or other foods. The recommended daily dietary intake of vitamin D is 400 IU for children younger than 1 year, and 600 IU for those older than 1 year.
In addition, Long says, parents should ensure children get enough vitamin D in their diets. Foods rich on vitamin D include fish (sardines, salmon tuna), egg yolks, vitamin D-fortified milk, vitamin D-fortified orange juice, cereals, yogurt and cheese.
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