Nutritional Status of Children Participating in the Special Supplemental Nutrition Program for Women, Infants, and Children -- United States, 1988-1991

Recent increases in the prevalence of overweight among school-aged children (1) and adults (2) in the United States have prompted concern about an increase in overweight among preschool-aged children and a possible association with the foods provided by the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). To assess and compare weight status and nutrient intake among WIC participants and other low-income children, CDC analyzed data from phase 1 of the Third National Health and Nutrition Examination Survey (NHANES III), 1988-1991. This report summarizes the results of this analysis, which indicate that foods provided by WIC are not associated with increased overweight among preschool-aged children.

CDC's NHANES III is a stratified multistage probability sample of the civilian, noninstitutionalized U.S. population aged greater than or equal to 2 months. The survey consists of two 3-year nationally representative samples (phase 1, 1988-1991 and phase 2, 1991-1994) with oversampling of children aged 2 months-5 years. A standardized physical examination in a mobile examination center included a 24-hour dietary recall and measurements of recumbent length (children aged less than 2 years for this analysis), stature (children aged greater than or equal to 2 years), and weight (3). Weight status is defined as weight-for-height in relation to the National Center for Health Statistics (NCHS)/CDC reference growth curves (4). Mean Z-scores (i.e., the average number of standard deviations a child is from the NCHS/CDC reference mean) are presented for non-Hispanic whites, non-Hispanic blacks, and Mexican Americans aged 2-23 months and 24-59 months. * Mean intakes of energy, percentage of energy from fat, calcium, and calcium per 1000 kilocalories (kcal) also are presented for these subgroups. Data were analyzed by race/ethnicity because, among low-income preschool-aged children, some racial/ethnic groups have a higher prevalence of high weight-for-height than other groups (5).

Among low-income (less than or equal to 185% of the poverty level **) white and black children, differences in weight status among those who participated in WIC and those who did not participate were neither significant nor consistent (Table_1). However, mean weight-for-height Z-scores were lower among Mexican American WIC participants than nonparticipants. Multivariate analyses indicate that when income is accounted for, the relation between WIC and weight-for-height remains the same.

Nutrient intakes varied by WIC participation (Table_2): although average energy intake was lower among WIC participants than non-WIC participants, both groups received approximately the recommended dietary allowance (RDA) for energy -- a pattern consistent among racial/ethnic groups. In general, the percentage of energy obtained from consuming fat was higher for WIC participants than nonparticipants, and all groups aged 24-59 months consumed above the dietary guideline of 30% of energy from fat (7). Calcium intake per 1000 kcal of energy also was higher in general for WIC participants than nonparticipants. Total calcium intake generally was higher for WIC participants aged 24-59 months, but lower for those aged less than 2 years. Black participants consumed more calcium from milk than did nonparticipants. Mean calcium intake for all WIC participants was approximately the RDA.

Reported by: Div of Health Examination Statistics, National Center for Health Statistics; Maternal and Child Health Br, Div of Nutrition, National Center for Chronic Disease Prevention and Health Promotion, CDC.

Editorial Note

Editorial Note: In 1972, the federal government established the WIC program following a determination of poor nutritional status among many low-income children in the United States (8). To participate in WIC, pregnant and postpartum women, infants, and children aged less than 5 years must meet income and nutritional risk criteria. The income criterion is determined by state agencies, but usually is not greater than 185% of the poverty level. Nutritional risk is defined as detrimental conditions detectable by biochemical or anthropometric measurements, other documented nutritionally related medical conditions, dietary deficiencies that impair health, or conditions (e.g., drug addiction) that increase the likelihood of inadequate nutritional patterns or nutritionally related medical problems. WIC provides nutrition education, referrals to health services, and supplemental foods high in protein, iron, calcium, vitamin A, and vitamin C. In 1994, approximately 3.2 million children aged 1-4 years and approximately 40% of all babies born in the United States participated in WIC (9).

In 1973, CDC, in collaboration with five states, initiated the Pediatric Nutrition Surveillance System (PedNSS) to continuously monitor the nutritional status of children who participate in publicly funded health and nutrition programs such as WIC. By 1990, this system had expanded to include 40 states, Puerto Rico, the District of Columbia, the Navajo Nation, and the Intertribal Council of Arizona. Each visit a child makes to a participating clinic generates a surveillance record that includes height and weight measurements. From 1980 through 1991, the prevalences of both low weight-for-height and high weight-for-height among white and black children participating in PedNSS remained stable at below the expected value of 5% (Mexican American children in PedNSS were not separated from other Hispanic children {10}). The 1990 PedNSS data are consistent with the finding that children who participate in WIC were not more overweight than other low-income children. In general, mean weight-for-height Z-scores from PedNSS were lower than the NHANES III mean values for WIC participants.

The findings in this report are subject to at least two limitations. First, the small sample sizes for some subgroups of WIC participants in the NHANES III data are associated with unstable estimates when based only on phase 1 data. Second, children who were not participating in WIC may not have been at nutritional risk and therefore may not have been eligible for participation in WIC. Thus, nutrient intake data differences between WIC and non-WIC participants who are WIC eligible may actually be greater than that observed in this analysis.

WIC foods provide necessary nutrients without contributing to overweight. However, overweight remains a public health problem in the United States. Health departments and other agencies that administer WIC should continue to reinforce the Dietary Guidelines for Americans (7), emphasizing the importance of diets lower in fat (for those aged greater than or equal to 2 years) and higher in calcium through consumption of foods such as low-fat dairy products.

References

1. Troiano RP, Flegal KM, Kuczmarski RJ, Campbell SM, Johnson CL. Overweight prevalence and trends for children and adolescents: the National Health and Nutrition Examination Surveys, 1963 to 1991. Arch Pediatr Adolesc Med 1995;149:1085-91.

2. Kuczmarski RJ, Flegal KM, Campbell SM, Johnson CL. Increasing prevalence of overweight among US adults. JAMA 1994;272:205-11.

3. NCHS. Plan and operation of the Third National Health and Nutrition Examination Survey, 1988-94. Hyattsville, Maryland: US Department of Health and Human Services, Public Health Service, CDC, NCHS, 1994; DHHS publication no. (PHS)94-1308. (Vital and health statistics; series 1, no. 32).

4. Dibley MJ, Goldsby JB, Staehling NW, Trowbridge FL. Development of normalized curves for the international growth reference: historical and technical considerations. Am J Clin Nutr 1987;46:736-48.

5. CDC. Nutritional status of minority children -- United States, 1986. MMWR 1987;36:366-9.

6. Dibley MJ, Staehling N, Nieburg P, Trowbridge FL. Interpretation of Z-score anthropometric indicators derived from the international growth reference. Am J Clin Nutr 1987;46:749-62.

7. US Department of Agriculture/US Department of Health and Human Services. Dietary guidelines for Americans. 4th ed. Washington, DC: US Department of Agriculture/US Department of Health and Human Services, 1995. (Home and garden bulletin, no. 232).

8. CDC. Ten-state nutrition survey, 1968-1970. Part III: clinical, anthropometry, dental. Atlanta: US Department of Health and Human Services, Public Health Service, CDC, 1972; DHEW publication no. 72-8131 (HSM).

9. US Department of Agriculture, Randall B, Boast L. Study of WIC participant and program characteristics, 1992. Washington, DC: US Department of Agriculture, Food and Nutrition Service, Office of Analysis and Evaluation, 1994.

10. CDC. Pediatric Nutrition Surveillance System -- United States, 1980-1991, and Pregnancy Nutrition Surveillance System -- United States, 1979-1990. MMWR 1992;41(no. SS-7).

* Numbers for other racial/ethnic groups were too small for meaningful analysis. ** Poverty statistics are based on a definition originated by the Social Security Administration in 1964, subsequently modified by federal interagency committees in 1969 and 1980, and prescribed by the Office of Management and Budget as the standard to be used by federal agencies for statistical purposes.

TABLE 1. Mean Z-score * weight-for-height for children aged 2-59 months,
by race/ethnicity +, age, and Special Supplemental Nurtrition Program for
Women, Infants and Children (WIC) participation status -- United States,
National Health and Nutrition Examination Survey III, Phase I, 1988-1991
============================================================================
                          WIC          Non-WIC &
Race/Ethnicity/      -------------   ------------      (95% CL **
  Age (mos)            No.   Mean @   No.   Mean    of difference)
----------------------------------------------------------------------------
White, non-Hispanic
          2-23                134   0.36     160   0.41     (-0.3, 0.1)
         24-59                 22    ++      166   0.15
         Total                156   0.33     326   0.23     (-0.2, 0.4)

Black, non-Hispanic
          2-23                151   0.62      95   0.44     (-0.1, 0.5)
         24-59                104   0.01     263   0.14     (-0.4, 0.2)
         Total                255   0.37     358   0.22     (-0.1, 0.3)

Mexican American
          2-23               130   0.25     118   0.39     (-0.5, 0.3)
         24-59                56   0.06     345   0.57          &&
         Total               186   0.20     463   0.53     (-0.6, 0.0)
----------------------------------------------------------------------------
*  Number of standard deviations from the National Center for Health
   Statistics/CDC reference mean.
+  Numbers for other racial/ethnic groups were too small for meaningful
   analysis.
&  Children not participating in WIC but living in families with incomes
   <=185% of the poverty level.
@  Z-scores between age groups within each racial/ethnic group are
   influenced by a disjunction in the growth charts at age 2 years (6).
** Confidence limit.
++ Sample size was too small to calculate an estimate.
@@ Potentially unreliable estimate because of small sample size.
============================================================================

TABLE 2. Mean nutrient intake for children aged 2-59 months, by race/ethnicity*, age, and Special Supplemental
Nutrition Program for Women, Infants and Children (WIC) participation status -- United States, National Health
and Nutrition Examination Survey III, Phase I, 1988-1991
===================================================================================================================
                      Energy (kcal) +          % Fat               Calcium per 1000 kcal     Calcium (mg) +
                  ---------------------  ---------------------    ----------------------- -------------------------
Race/Ethnicity/         Non-                    Non-                    Non-                   Non-
 Age (mos)        WIC   WIC    95% CL@    WIC   WIC    95% CI      WIC  WIC    95% CI     WIC  WIC    95%CI
-------------------------------------------------------------------------------------------------------------------
White,
 non-Hispanic
  2-23           1034  1095 (-197,   76)  37.0  35.4  (-1.3, 4.5)  793  847  (-124,  17)  784  882  (-174,  -22)
 24-59            **   1479                **   34.3               **   554               **   802
 Total           1194  1368 (-320,  -30)  35.4  34.6  (-0.5, 2.1)  724  638  (  32, 141)  812  825  ( -90,   66)

Black,
 non-Hispanic
  2-23           1019  1209 (-294,  -87)  36.8  36.9  (-1.8, 1.6)  721  642  (   0, 157)  702  753  ( -166,  64)
 24-59           1573  1609 (-173,  102)  37.9  35.3  ( 0.6, 4.6)  498  412  (  50, 122)  774  661  (   27, 200)
 Total           1247  1510 (-358, -167)  37.3  35.7  ( 0.3, 2.9)  629  469  ( 107, 213)  732  684  (  -25, 121)

Mexican American
  2-23            977  1117 (-236,  -44)  37.4  35.9  (-0.4, 4.2)  815  869  ( -173, 67)  767  923  (-230,  -82)
 24-59           1503  1434      ++       33.2  33.6       ++      564  565       ++      843  804       ++
 Total           1133  1364 (-375,  -89)  36.1  34.1  ( 0.5, 4.1)  741  631  (  18, 201)  790  830  (-104,   23)
-------------------------------------------------------------------------------------------------------------------
*  Numbers for other racial/ethnic groups were too small for meaningful analysis.
+  Recommended daily allowance of 850 kilocalories (kcal) and 600 mg calcium for ages 6-11 months, 1300 kcal for
   ages 12-47 months; 1800 kcal for ages 48-59 months; and 800 mg calcium for ages 12-59 months.
&  Children not participating in WIC but living in families with incomes <=185% of the poverty level.
@  95% confidence limit around the difference in means.
** Sample size was too small to calculate an estimate.
++ Potentially unreliable estimate because of small sample size.
===================================================================================================================

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