Childhood is a time of economic turmoil and hardship for many U.S. children, with 49 percent living in households that use food stamps, researchers say.

"Food stamp use is a clear sign of poverty and food insecurity, two of the most detrimental economic conditions affecting a child's health," Mark R. Rank, a poverty expert at the George Warren Brown School of Social Work at Washington University in St. Louis, says in a statement.

The substantial risk of a child being in a family that uses food stamps is consistent with a wider body of research demonstrating U.S. children face considerable economic risk throughout their childhood years.

"Rather than being a time of security and safety, the childhood years for many American children are a time of economic turmoil, risk, and hardship," Rank says.

Rank's study, published in the Archives of Pediatrics & Adolescent Medicine says:

-- 90 percent of black children and 37 percent of white children will be in a household that uses food stamps.

-- Nearly one-quarter of all American children will be in households that use food stamps for five or more years during childhood.

-- 91 percent of children with single parents will be in a household receiving food stamps, compared to 37 percent of children in married households.