The 'age+5' rule: comparisons of dietary fiber intake among 4- to 10-year-old children.

Objective 2.6 of Healthy People 2000 (1) proposes that, by the end of the decade, American adults should be consuming at least 5 servings of vegetables and fruits dally and at least 6 servings of grains daily. The dietary fiber found in these foods is thought to protect against constipation (2), obesity (3,4), cardiovascular disease (5,6), some cancers (7), and diabetes (8). Unfortunately, because of limited data, the US Department of Health and Human Services was not able to expand this objective specifically to include children. Omitting children from the objective, although understandable, is unfortunate, because these diseases may originate during childhood (9). Because vegetables, fruits, and grains are good sources of fiber and essential and nonessential nutrients, parents should ensure that their children consume adequate amounts of these foods.

Despite the fact that a federally recognized standard for dietary fiber intake during childhood does not yet exist (10), the American Academy of Pediatrics Committee on Nutrition (11) has recommended that children consume 0.5 g dietary fiber for every 1 kg body weight (with an tipper limit of 35 g/day). Although this amount is healthful for most children, fiber intakes for male adolescents may be too high, particularly if their intake of essential minerals (ie, calcium, iron, and zinc) is low. A second recommendation that children consume 10 g dietary fiber for every 1,000 kcal consumed may provide excessive fiber for small or young children (12). For more practical reasons, the utility of these formulas must be questioned, because most parents would find them too complex for determining their children's optimal dietary fiber intake.

In May 1994 the American Health Foundation recommended that children at least 2 years old should consume daily an amount of fiber that is equal to their age plus an additional 5 g dietary fiber (13,14). For example based on this "age+5" rule, a 3-year-old should consume at least 8 g dietary fiber daily. This recommendation holds throughout childhood and adolescence until the age of 20 years, after which intakes of 25 to 35 g dietary fiber per day are recommended for healthy adults (15).

Recognizing that a lack of data excluded children from objective 2.6 of Healthy People 2000, several studies have been conducted since then to examine dietary fiber intake during childhood; however, many of these focused on older children and adolescents (16-20), or they obtained generic values for fiber intake by averaging values over a wide range of years (21). Two studies did compare children's fiber intake to the age+5 rule, but their analyses were limited by a small sample size (21), the use of a data set possibly biased by a low response rate (22), and a limited number of food group categories that could not distinguish between low- and high-fiber foods within a category (22).

Because of the attention paid to the age+5 rule by consumers, health educators, and food manufacturers (23), we used a large national data set to determine what percentage of children were meeting the American Health Foundation's age+5 recommendation and what the leading contributors to total dietary fiber intake were. Because of the frequently cited risk that a very-high-fiber diet can satiate a child before an adequate amount of nutrients is ingested or absorbed (9,12-14), intakes of food and nutrients between those who did and did not meet the age+5 rule were also compared.

METHODS

Data were obtained from the 1989-1991 Continuing Survey of Food Intakes by Individuals (CSFII). These surveys included men, women, and children who resided in the 48 contiguous states. Methods used to conduct these multistage, stratified-area, probability surveys have been previously documented (24,25). Our study included data from 603 children between the ages of 4 and 6 years and 782 children between the ages of 7 and 10 years. These age categories were chosen because they matched those of the Recommended Dietary Allowances (RDAs) (26). All 1,385 of the children had one 24-hour food recall and two 1-day food records completed for them by a knowledgeable adult, generally the child's primary caregiver.

The US Department of Agriculture (USDA) released each of the CSFII data sets separately; however, because they were released with labels and a fixed format, all 3 surveys were combined for data processing into 1 large data set. The USDA assigned each food and beverage item a 7-digit code number and provided food groups to categorize them. However, these food groups were found to be too broad for the purposes of this investigation because low- and high-fiber foods in a category could not be distinguished adequately. Instead, food and beverage items reported as consumed were recoded and recategorized into 41 major food groups using previous research as a guide (27,28). Food groups were created to identify dietary sources of fiber and to differentiate between fiber-rich and fiber-poor foods in a category. …