In both studies, critically ill children deficient in the vitamin were more likely than those with adequate blood levels of vitamin D to be sicker and have longer hospital stays.

Earlier studies have linked vitamin D deficiency with worse outcomes in critically ill adults, and the new findings suggest that the same thing may be true for children, researchers say.

However, it is not yet clear if screening sick children for vitamin D deficiency and treating those who are deficient with supplements can improve their outcomes.

"We certainly think this is something that deserves further study," says pediatric critical care specialist Kate Madden, MD, of Children's Hospital Boston and Harvard Medical School.

Both studies are scheduled for publication in the September issue of the journal Pediatrics.

In one, Madden and colleagues conducted vitamin D screenings on about 500 children admitted to the hospital's pediatric intensive care unit (PICU) over a 12-month period.

They found that 2 in 5 children (40%) were deficient in the vitamin and that vitamin D deficiency was associated with more severe illness on admission to the hospital.

A second study conducted by researchers from the Children's Hospital of Eastern Ontario included about 300 critically ill children and teenagers.

In that trial, almost 70% of the participants were vitamin D deficient when tested, and deficiency was independently associated with longer ICU stays and more severe illness.

In both studies, vitamin D deficiency was considerably more common than has been reported in healthy children and adolescents.

The Institute of Medicine (IOM) recommends that children over the age of 1 get 600 international units (IU) of the vitamin daily.

Pediatrics professor Steven A. Abrams, MD, of Houston's Baylor College of Medicine and Texas Children's Hospital, served on the IOM committee that came up with the guidelines.

The American Academy of Pediatrics (AAP) recommends a slightly lower dose of Vitamin D, 400 IU per day. They also recommend that all children and adolescents take a vitamin daily for this.

Abrams tells WebMD that children can get this much vitamin D by eating dairy products and foods fortified with the vitamin. Examples include milk and yogurt. Orange juice, oily fish, egg yolks, and mushrooms also contain vitamin D.

Children in the Boston study who took a multivitamin every day had significantly higher vitamin D levels and were less likely to be deficient than children who didn't.

Most children's multivitamins have about 400 IU of vitamin D.

In an editorial published with the studies, Abrams and colleague Jorge A. Coss-Bu, MD, concluded that it is too soon to recommend routine testing of all children admitted to pediatric ICUs for vitamin D deficiency.

Abrams says it remains to be determined if vitamin D deficiency causes poorer outcomes in critically ill children or if it is an indicator for something else, such as poor general nutritional status.

"There is increasing evidence linking low vitamin D status to various health problems," he says. "One message is that avoiding vitamin D deficiency appears to be beneficial, but that doesn't mean people have to take large doses of supplements to get what they need."

(Source: http://children.webmd.com/news/20120806/vitamin-d-deficiency-common-sick-kids )