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U.S. Department of Health and Human Services


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Consumer Research on Infant Formula and Infant Feeding

Below are research abstracts of consumer research studies conducted or supported by the Center for Food Safety and Applied Nutrition.

A Longitudinal Analysis of Infant Morbidity and the Extent of Breastfeeding in the United States.
1997. Paula D. Scariati, Laurence M. Grummer-Strawn and Sara Beck Fein. Pediatrics 99(6):e5 (Electronic Article)

Background: Studies on the health benefits of breastfeeding in developed countries have shown conflicting results. These studies often fail to account for confounding, reverse causality, and dose-response effects. We addressed these issues in analyzing longitudinal data to determine if breastfeeding protects US infants from developing diarrhea and ear infections.

Methods: Mothers participating in a mail panel provided information on their infants at ages 2, 3, 4, 5, 6, and 7 months. Infants were classified as exclusively breastfed; high, middle, or low mixed breast-and formula-fed; or exclusively formula-fed. Diarrhea and ear infection diagnoses were based on mothers' reports. Infant age and gender; other liquid and solid intake; maternal education, occupation, and smoking; household size; family income; and day care use were adjusted for in the full models.

Results: The risk of developing either diarrhea or ear infection increased as the amount of breast milk an infant received decreased. In the full models, the risk for diarrhea remained significant only in infants who received no breast milk compared with those who received only breast milk (odds ratio = 1.8); the risk for ear infection remained significant in the low mixed feeding group (odds ratio = 1.6) and among infants receiving no breast milk compared with those who received only breast milk (odds ratio = 1.7).

Conclusions: Breastfeeding protects US infants against the development of diarrhea and ear infection. Breastfeeding does not have to be exclusive to confer this benefit. In fact, protection is afforded in a dose-response manner. The more breast milk an infant receives in the first 6 months of life, the less likely that he or she will develop diarrhea or ear infection.

Risk of Diarrhea Related to Iron Content of Infant Formula: Lack of Evidence to support the Use of Low-iron Formula as a supplement for Breastfed Infants.
1997. Paula D. Scariati, Laurence M. Grummer-Strawn, Sara Beck Fein, and Ray Yip. Pediatrics 99(3):e2.

Background: Concern has been raised by infant feeding experts that supplementing breastfed infants with iron-fortified formula rather than low-iron formula may have an undesirable impact on their gastrointestinal flora. Thus far, there have been no clinical studies to address this issue directly. We compared the reported frequency of diarrhea for breastfed infants given iron-fortified formula with those fed low-iron formula.

Methods: Mothers participating in a mail panel provided feeding and diarrhea information on their infants at 2, 3, 4, 5, 6, 7, 9, and 12 months (n = 1743). Infants were grouped into five feeding categories: (1) breast milk only, (2) breast milk and low-iron formula, (3) breast milk and iron-fortified formula, (4) low-iron formula only, and (5) iron-fortified formula only. We calculated the number of diarrheal episodes per week for each feeding category and used rate ratios to estimate the relative impact of low-iron and iron-fortified formulas.

Results: Among infants who received both breast milk and formula, the rate ratio for iron-fortified formula versus low-iron formula was 1.06 (confidence interval, 0.84 to 1.34), indicating that the type of formula a breastfed infant receives does not significantly affect the frequency of diarrhea.

Conclusions: We found no evidence to support the hypothesis that breastfed infants given iron-fortified formula are at greater risk of having diarrhea. This, in addition to the fact that iron-fortified formula has played a major role in preventing childhood iron deficiency anemia, supports the current recommendation that any formula given to infants be fortified with iron. food, diarrhea, breastfeeding, iron.

Water Supplementation of Infants in the First Month of Life.
1997. Paula D. Scariati, DO, MPH, Laurence M. Grummer-Strawn, PhD; Sara Beck Fein, PhD. Archives of Pediatrics & Adolescent Medicine. 151:830-832.

Objective: To describe the prevalence of and risk factors associated with regular water supplementation of neonates, considering infant feeding status, mother's education, and family income.

Design: Evaluation of data from the Food and Drug Administration's Infant Feeding Practices Study, a panel study of US women of fairly high socioeconomic status who were followed up from late pregnancy through their infants' first year of life. The sample was drawn from a nationally distributed consumer mail panel. Each mother was asked whether she gave her neonate water at least 3 times per week.

Participants: A total of 1677 mothers of infants who were neonates in April through November 1993.

Main Outcome Measures: Percentages of mothers who gave their neonates water at least 3 times a week.

Results: About one fourth (24.7%) of the mothers reported giving their neonates water at least 3 times per week. Stratification by feeding practices and socioeconomic factors revealed that 41.6% of mothers who formula-fed their neonates, 47.4% of mothers with less than a high school education, and 35.4% of mothers with an annual family income less than $22,500 gave their neonates water at least 3 times per week.

Conclusions: Water supplementation of neonates was a prevalent practice in this cohort of women. Feeding practices, maternal education, and family income were all significant risk factors associated with this behavior.

The Effect of Work Status on Initiation and Duration of Breast-Feeding.
1998. Sara B. Fein, PhD, and Brian Roe, PhD. A. American Journal of Public Health. 88:1042-1046

Objectives: In this study, longitudinal data are used to examine the effect of work status on breast-feeding initiation and duration.

Methods: Mothers from a mail panel completed questionnaires during late pregnancy and 10 times in the infant's first year. Mother's work status was categorized for initiation by hours she expected, before delivery to work and for duration by hours she worked at month 3. Covariates were demographics, parity, medical, delivery, and hospital experiences, social support, embarrassment, and health promotion.

Results: Expecting to work part-time neither decreased nor increased the probability of breast-feeding relative to expecting not to work (odds ratios [ORs] =.83 and .99, P>.50), but expecting to work full-time decreased the probability of breast-feeding (OR= .47, P < .0l). Working full-time at 3 months postpartum decreased breast feeding duration by an average of 8.6 weeks (P<.001) relative to not working, but part-time work of 4 or fewer hours per day did not affect duration, and part-time work of more than 4 hours per day decreased duration less than full-time work.

Conclusion: Part-time work is an effective strategy to help mothers combine breast-feeding and employment.

Is There Competition Between Breast-Feeding and Maternal Employment?
1999. Brian Roe, Leslie A. Whittington, Sara Beck Fein, and Mario F. Teisl. Demography. 36(2):157-171.

Theory suggests that the decision to return to employment after childbirth and the decision to breast-feed may be jointly determined. We estimate models of simultaneous equations for two different aspects of the relationship between maternal employment and breastfeeding using 1993-1994 data from the U.S. Food and Drug Administration's Infant Feeding Practices Study. We first explore the simultaneous duration of breast-feeding and work leave following childbirth. We find that the duration of leave from work significantly affects the duration of breast-feeding, but the effect of breastfeeding on work leave is insignificant. We also estimate models of the daily hours of work and breast feedings at infant ages 3 months and 6 months postpartum. At both times, the intensity of work effort significantly affects the intensity of breast-feeding, but the reverse is generally not found. Competition clearly exists between work and breast-feeding for many women in our sample.

Medically Advised, Mother's Personal Target, and Actual Weight Gain During Pregnancy.
1999. Mary E. Cogswell, Kelley S. Scanlon, Sara Beck Fein, and Laura A. Schieve. Obstetrics and Gynecology. 94(4):616-622.

Objective: To evaluate whether advice on pregnancy weight gain from health care professionals, women's target weight gain (how much weight women thought they should gain), and actual weight gain corresponded with the 1990 Institute of Medicine recommendations.

Methods: Predominantly white, middle-class women participating in a mail panel reported their prepregnancy weights, heights, and advised and target weight gains on a prenatal questionnaire (n = 2237), and their actual weight gains on a neonatal questionnaire (n = 1661). Recommended weight gains were categorized for women with low body mass index (BMI) (less than 19.8 kg/m2) as 25-39 lb; for women with average BMI (19.8-26.0 kg/m2) as 25-34 lb; and for women with high BMI (more than 26.0-29.0 kg/m2) and very high BMI (more than 29.0 kg/m2) as 15-24 lb.

Results: Twenty-seven percent of the women reported that they had received no medical advice about pregnancy weight gain. Among those who received advice, 14% (95% confidence interval 1CIl 12%, 16%) had been advised to gain less than the recommended range and 22% (95% Cl 20%, 24%) had been advised to gain more than recommended. The odds of being advised to gain more than recommended were higher among women with high BMIs and with very high BMIs compared with women with average BMIs. Black women were more likely than white women to report advice to gain less than recommended. Advised and target weight gains were associated strongly with actual weight gain. Receiving no advice was associated with weight gain outside the recommendations.

Conclusion: Greater efforts are required to improve medical advice about weight gain during pregnancy.

Contact Linda.Verrill@fda.hhs.gov for more information about the above studies.