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The Challenges of Promoting Optimal Infant Growth ³

Department of Nutrition and Program in International Nutrition, University of California

¹To whom correspondence should be addressed. E-mail: kgdewey{at}ucdavis.edu

	INTRODUCTION

TOP INTRODUCTION REFERENCES

 
Safe and adequate complementary feeding of breastfed infants is well recognized as a critical factor in preventing child malnutrition. In disadvantaged populations, growth faltering is most evident in the first year of life, and is often accompanied by micronutrient deficiencies and high rates of infection. After two years of age, it is very difficult to reverse the growth stunting that has occurred earlier. Thus, it is essential to identify interventions that are effective in promoting optimal growth and development in early life.

Several recent documents have prompted greater attention to complementary feeding (1 2 3) , and there is intense interest among policy makers in implementing effective programs. Unfortunately, there have been very few well-designed intervention trials to evaluate the efficacy and effectiveness of various strategies for improving complementary feeding. As a result, the scientific base for advising policy makers is much thinner than desirable. The few studies available indicate that it is certainly possible to improve feeding practices, but the impact on growth and other functional outcomes has been mixed. For example, among 10 efficacy trials in which an enhanced or fortified complementary food was provided free of charge to infants of various ages, only three demonstrated an increase in linear growth (3) . There are many possible reasons for the lack of impact in the other trials, such as targeting the intervention too early (e.g., before 6 mo) or too late (e.g., after 12 mo); methodological limitations such as small sample size, short duration of the intervention, or attrition bias; and constraints on growth response due to infections, prenatal "programming" or other factors.

In this context, the intervention study conducted by Bhandari et al. (4) in an urban slum in India makes an especially important contribution. The researchers used a strong experimental design: a randomized controlled trial that evaluated the effects of providing a micronutrient-fortified complementary food (with nutritional counseling) or nutritional counseling alone on infant complementary food intake, growth and morbidity between 4 and 12 mo of age. They included two different control groups: one that received the same number of home visits as the two intervention groups (twice weekly), and one that was visited only three times for measurements. The former group ("visitation group") was defined a priori as the most relevant control group for data analysis. Strengths of the study include a relatively generous sample size (>100 infants per group), reasonably low attrition rates, documentation of use of the fortified food, and careful frequent assessments of growth and morbidity. In the food supplementation group, packets of the fortified food were delivered to the home twice a week and the mother was instructed to mix the instant powder with boiled water.

The researchers report a modest increase in weight gain (250 g over 8 mo) in the food supplementation group, but no significant effect on length gain, and no growth impact of nutritional counseling alone. The weight gain difference in the food supplementation group was almost entirely attributable to differences between 6 and 9 mo, with no significant difference among groups in the earlier (4 to 6 mo) or later (9 to 12 mo) age intervals. Compared to expected growth rates of breastfed infants at these ages (5) , weight and length gain of these Indian infants was normal between 4 and 6 mo, but well below normal subsequently. The overall average "deficit" in weight gain between 4 and 12 mo was about 800 g in the control group. Thus, the fortified food resulted in making up about a third of this deficit.

The effects of food supplementation on breastfeeding, as well as some of the morbidity outcomes, were disconcerting. In the food supplementation group, breastfeeding frequency was significantly lower at 6 and 9 mo (by 1–2 feeds per day), and fewer infants were still being breastfed at 12 mo in comparison with the visitation group (84 vs 97%). Despite the advice to use boiled water, the prevalence rate of dysentery was twice as high in the food supplementation group and the prevalence of fever was increased by 44%. The authors speculate that the relatively small effect on weight gain, and the lack of impact on length gain, could be partially due to the adverse effects of this intervention on breastfeeding and morbidity.

What are the lessons to be learned from this study? The authors conclude that the infants’ energy intake from complementary foods may still have been lower than desirable, even in the food supplementation group, and suggest that there are barriers related to the amount of food offered by caregivers that need to be overcome. While this may be part of the explanation, there are other potential constraints on intake and growth that may be at least as important. First, restrictions on infant appetite due to micronutrient deficiencies or illness may play a major role. It is well known that zinc deficiency depresses appetite, and the same may be true for other nutrient deficiencies. Although the fortified food provided a reasonable amount of zinc compared to estimated needs at this age (1) , its bioavailability is uncertain. In the nutrition counseling group, the emphasis appears to have been on feeding frequency, portion size and energy density of complementary foods, rather than on micronutrient density. Moreover, in both intervention groups it is likely that many infants were of low birth weight and thus may have had low hepatic stores of zinc at birth (6) , which increases the vulnerability to zinc deficiency. Other micronutrients may also have been in short supply: based on the median reported intake of the fortified food (940 kJ/d) and assumed values for breast milk content (1 ,7) , the infants in the food supplementation group received adequate amounts of vitamin A, riboflavin and calcium, but insufficient vitamin B-6, phosphorus and iron to meet their needs. Deficiencies of any of these three nutrients could be linked to poor appetite. Suppression of appetite during illness, particularly for solid foods (though not for breast milk), is also well documented (8) . In infant feeding studies it is useful to observe complementary food intake over a 12-h period, to determine whether the infants are consuming all of the food offered, or are leaving a substantial portion of food unconsumed. In the latter situation, it may be that the caregiver is offering plenty of food, but the child’s appetite is impaired. The educational and programmatic implications are very different if this is a common scenario.

Second, the growth response to the fortified food may have been constrained by prenatal "programming" or intergenerational effects of maternal stunting. According to the baseline data, 25% of the infants were already stunted at 4 mo of age, a large proportion of which was presumably due to intrauterine growth retardation (IUGR).² Infants who experience IUGR usually never completely catch-up in size to their normal birth weight peers (9) , even when raised under optimal conditions. The lack of growth response to the intervention at 9–12 mo of age in the Indian infants is consistent with other reports documenting growth faltering at that age in disadvantaged populations, even when they are provided with adequate complementary foods (10) . Thus, researchers and planners must be realistic about the magnitude of any improvement in growth expected from postnatal interventions alone. It is likely that a combination of prenatal and postnatal approaches is the most effective strategy.

The study by Bhandari et al. also provides information relevant to the appropriate age for introduction of complementary foods, which has recently received considerable attention (11) . Evidence from two randomized intervention studies in Honduras indicates no growth advantage of introducing complementary foods at 4 mo, compared to exclusive breastfeeding for 6 mo (12 ,13) , but there have been no other randomized trials in other parts of the world. Although the Indian study was not designed to directly address this question (which would require a control group who was exclusively breastfed for six months), the data are nonetheless informative because the "visitation" group received very little energy from nonbreast milk sources prior to six months (a median of only 192 kJ/d at 6 mo). Despite the fact that the food supplementation group received far more energy from complementary foods (1111 kJ/d at 6 mo), their average weight and length gains from 4 to 6 mo were identical to those of the visitation group (0.97 kg and 4.1 cm). These results, plus the observation that the growth rates of these infants at 4–6 mo were at or above expected values for breastfed infants (5) , suggest that near-exclusive breastfeeding for six months is compatible with normal growth even in a population in which maternal malnutrition is prevalent.

In conclusion, the results of the intervention trial reported by Bhandari et al. illustrate the need to better understand the etiology of infant growth faltering. In particular, researchers and program planners need to pay special attention to the potential impact of complementary food interventions on rates of breastfeeding and the prevalence of illness, and not assume that merely increasing complementary food intake will have the desired impact. This is one situation in which "more" is not necessarily "better," because of the tradeoff between intake of complementary foods and intake of breast milk. In fact, had the infants in the food supplementation group actually consumed the recommended numbers of food packets per day, they would have met their total energy needs from the fortified food alone, leaving no room for energy from breast milk. Planners sometimes justify providing more than needed, to allow for individual variability and the possibility of catch-up growth, but in so doing they must recognize that there are risks associated with "overshooting." Comprehensive approaches that address the full range of prenatal and postnatal influences on growth are needed to reduce the rates of stunting in malnourished populations.

	FOOTNOTES

 
² Abbreviations: IUGR, intrauterine growth retardation.

³ See related article: J. Nutr. 131: 1946–1951, 2001

	REFERENCES

TOP INTRODUCTION REFERENCES

 

1. WHO Complementary feeding of young children in developing countries: a review of current scientific knowledge 1998 World Health Organization Geneva. WHO/NUT/98.1,

2. WHO Complementary feeding: family foods for breastfed children 2000 World Health Organization Geneva. WHO/NCH/00.1,

3. Dewey K. G. Approaches for improving complementary feeding of infants and young children 2001 World Health Organization Geneva. in press

4. Bhandari N., Bahl R., Nayyar B., Khokhar P., Rohde J. E., Bhan M. K. A randomized trial to assess the growth impact of food supplementation and nutritional counselling in infants between 4 and 12 months of age. J. Nutr. 2001;131:1946-1951[Abstract/Free Full Text]

5. WHO Working Group on Infant Growth An evaluation of infant growth 1994 World Health Organization Geneva. WHO/NUT/94.8,

6. Zlotkin S. H., Cherian M. G. Hepatic metallothionein as a source of zinc and cysteine during the first year of life. Ped. Res. 1988;24:326-329[Medline]

7. Dewey K. G. Nutrition, growth, and complementary feeding of the breastfed infant. Ped. Clin. N. Amer. 2001;48:87-104

8. Brown K. H., Stallings R. Y., Creed de Kanashiro H., Lopez de Romana G., Black R. E. Effects of common illnesses on infants’ energy intakes from breast milk and other foods during longitudinal community-based studies in Huascar (Lima), Peru. Am. J. Clin. Nutr. 1990;52:1005-1013[Abstract/Free Full Text]

9. Martorell R., Ramakrishnan U., Schroeder D. G., Melgar P., Neufeld L. Intrauterine growth retardation, body size, body composition and physical performance in adolescence. Eur. J. Clin. Nutr. 1998;52:S1, S43-S1, S53

10. Dewey K. G. Cross-cultural patterns of growth and nutritional status of breast-fed infants. Am. J. Clin. Nutr. 1998;67:10-17[Abstract]

11. WHO (2001) Note for the press. The optimal duration of exclusive breastfeeding: results of a WHO systematic review. http//www.who.int/inf-pr-2001/en/note2001–07.html.

12. Cohen R. J., Brown K. H., Canahuati J., Landa Rivera L., Dewey K. G. Effects of age of introduction of complementary foods on infant breast milk intake, total energy intake, and growth: a randomised intervention study in Honduras. Lancet 1994;344:288-293[Medline]

13. Dewey K. G., Cohen R. J., Brown K. H., Landa Rivera L. Age of introduction of complementary food and growth of term, low birth weight breastfed infants: a randomized intervention study in Honduras. Am. J. Clin. Nutr. 1999;69:679-686[Abstract/Free Full Text]

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