Vitamin D deficiency is a growing problem in the United States. A 2004 study reported that 42 percent of otherwise healthy adolescents in a primary care setting were vitamin D deficient. Among infants, dark skin pigmentation and breastfeeding without supplementation have been cited as risk factors. Most studies have examined infants, but there are fewer data as to whether this problem persists as children are weaned to fortified milk and solid foods. A new study should raise a red flag for parents.
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The authors of this new study recruited children eight to 24 months of age for skin pigmentation, nutritional intake, and breastfeeding history. They also did a blood test for vitamin D (serum 25-hydroxyvitamin D level).
The results were stunning. Of the 365 children, a whopping 40 percent (146 kids) had suboptimal vitamin D levels. Of these kids, 44 children (12.1 percent) were vitamin D deficient.
Infants and toddlers were equally susceptible; however, infants who were breastfed without supplementation were 10 times more likely to be vitamin D deficient compared with infants who were exclusively bottle-fed.
Among toddlers, milk consumption significantly reduced the chance of vitamin D.
No correlation was found between vitamin D deficiency and sex, time spent outdoors, sunscreen use, sun sensitivity, or skin pigmentation.
The authors conclude that vitamin D deficiency is common among infants and toddlers, and is strongly associated with breastfeeding without supplementation among infants.
These findings support current recommendations for vitamin D supplementation for all young children, and the authors recommend that this be emphasized for all breastfed infants for the duration of breastfeeding.
The editor of American Family Physician writes:

• Vitamin D deficiency had been virtually eliminated in the United States by the 1950s because of sunlight exposure and fortifying milk with vitamin D.
• Recently, however, reports of vitamin D deficiency and rickets among U.S. children have been increasing.
• A clinical review in the same journal concluded that subclinical vitamin D deficiency is widespread among children of all ages and ethnicities, with potential long-term effects on bone health and the development of several chronic diseases.
• Although vitamin D deficiency is recognized as a problem, there is much discussion as to what constitutes “good” levels of vitamin D.
• One review found improved clinical outcomes with vitamin D levels of 36 to 40 ng per mL (90 to 100 nmol per L).

To achieve these vitamin D levels, most adults would require more vitamin D (at least 700 to 1,000 IU per day) than allowed for by current recommendations.
The current vitamin D recommendation for U.S. children was increased from 200 IU per day to 400 IU per day just last year.
A blood test, the serum 25-hydroxyvitamin D level is the best indicator of actual vitamin D status, because it reflects dietary intake and synthesis from skin, and has a half-life of about 15 days.
Here’s another of my other blogs on vitamin D in teens:

• Vitamin D recommendations for teens may be too low