Clinical evidence demonstrates that low fiber intakes put people at risk of chronic constipation. However, there are also other reasons to encourage fiber consumption in children, say the researchers.
"For example, fiber has been shown to lower cardiovascular risk in adults," said study leader Dr Sibylle Kranz, assistant professor of nutritional sciences at Penn State University.
"Children who eat high-fiber foods are more likely to grow up into adults who consume adequate fiber," she added.
The researchers also found that children who consumed the most fiber had the most nutrient-rich diets.
Reported in the February issue of the Journal of the American Dietetic Association (vol 105, no 2), the study estimated dietary fiber intakes based on two-day averages of 5,437 children whose parents provided information in the 1994-1996 and 1998 Continuing Survey of Food Intake by Individuals conducted by the US Department of Agriculture.
The researchers conducted separate analyses on the two and three-year-olds and the four- and five-year-olds and compared them.
The younger children had, on average, a higher fiber intake than the older children. The two and three year olds, whose fiber intake placed them in the top quarter of the sample, met the new National Academy of Sciences Dietary Reference Intake level of 14 g total fiber per every 1,000 calories for all ages based on evidence for reduced cardiovascular disease risk at that level.
The main fiber sources consumed by the children were low-fiber fruits, such as applesauce, legumes and high-fiber cereal. Other low-fiber, low-nutrient foods that contributed very small amounts of fiber to the children's diets included pizza and other high-fat, grain-based mixed dishes and high-fat salty snacks such as chips.
High-fiber vegetables and fruit, which should be a major source of fiber, were consumed in too small quantities to contribute to the total average fiber intake, said the researchers.
"An easy substitution to get more fiber into their diets is to change to whole-grain products and high-fiber cereals," said Krantz.
Resarch by Productscan last year suggests that food companies are increasingly trying to market the benefits of fiber. The percentage of new food and beverage products making high fiber claims in North America has been stuck at around 2.5 percent for the past four years, but a new survey by the firm revealed this figure had increased to 4.2 percent in 2004.