The study also found that the children who most need to take vitamins aren't getting them.

"Many of the children and adolescents who are using daily vitamin supplements do not need to take them, because they are receiving adequate nutrition from the foods they eat," said Ulfat Shaikh, lead study author, assistant professor of pediatrics at the UC Davis School of Medicine and a clinician at UC Davis Children's Hospital.

"Our study also indicates that children and adolescents who may face the greatest risks of vitamin and mineral deficiency are the least likely to be taking supplements," Shaikh said.

Shaikh and her colleagues analyzed data from 10,828 children between 2 and 17 years old who took part in the 1999 to 2004 National Health and Nutrition Examination Survey (NHANES). Children were considered to be vitamin and mineral supplement users if they had taken a supplement within the month preceding their inclusion in the survey. The researchers also looked at how much exercise they got, the types of foods they ate and whether or not they were covered by health insurance, among other factors.

"We wanted to know more about which children take vitamin and mineral supplements and whether vitamin and mineral supplements may be used by parents to prevent medical problems related to poor diet or lower food security," Shaikh said.

The American Academy of Pediatrics (AAP) does not recommend vitamin use in healthy children over 1 year old. Previous studies have shown that about one-third of children in the United States take a daily multi-vitamin. The current study found that children who are healthier, more active, eat a balanced diet and have greater access to health care are more likely to take vitamins. The study found that, among children who were in excellent health, 37 percent took vitamins. But only about 28 percent of children in fair or poor health took them.

"As expected, we found that a large number of underweight children had taken a multivitamin in the previous month. But we also found that between 30 and 40 percent of children who regularly eat vegetables and drink milk are taking supplements. Supplements for children and adolescents who are healthy and eat a varied diet are not only medically unnecessary but they are not regulated by the Food and Drug Administration (FDA)," Shaikh said.

In addition, overdose is more likely in 2- to 4-year-old children who may associate taking vitamins with eating candy, she said. Taken in large quantities, vitamin and mineral supplements can cause adverse effects ranging from vomiting to serious side effects, such as damage to the kidneys. Shaikh said that future research on this issue will likely include direct interviews with parents to find out why they chose to give their children vitamins in cases where a medical reason for vitamin and mineral supplement use may not be present.

"This is a descriptive study," Shaikh said. "The next step will be to explore with parents the reasons behind their decisions to provide their children with multi-vitamins."

The study also noted that socio-demographic factors influencing vitamin and mineral supplement use are the same ones that have been shown to interfere with children eating healthy diets, exercising regularly and maintaining a healthy body weight. The study proposes that cost may be one reason that children who need vitamins don't get them.

The study findings seem to bear out the hypothesis that cost is a barrier to children getting vitamins. Among households considered below the poverty level, 22 percent of children used vitamins. The number jumped to 43 percent among those not considered poor. Among households not enrolled in the federal Food Stamp Program, 38 percent of children used vitamins. But in households using food stamps, vitamin use was around 18 percent. Children in 36 percent of households where there is no hunger use vitamins; only 15 percent use vitamins in households where there is "food insecurity and hunger."

Source: University of California - Davis