Screening for nutrition interventions: the risk or the differential-benefit approach?

How can the scientific community support the generation of the evidence needed to improve the quality of guidelines for micronutrient interventions?

The process used by the WHO to generate nutrition recommendations relies on high-quality research evidence, and this makes new demands on the research questions that nutrition scientists address. As a researcher involved in WHO nutrition guidelines development, my objective is to suggest ways in which our research can adapt to meet these demands. Randomized controlled trials and systematic reviews generate the highest quality of evidence to support strong recommendations, yet even these methods leave controversies in which judgments must be made. Using examples from recent research and guidelines, 4 issues are highlighted that illustrate ways in which nutrition research can adapt to become more useful and informative to global nutrition guidelines. These issues include embedding mechanistic research within trials, explicit choice of design along the efficacy or effectiveness spectrum, anticipation of heterogeneity of effects, and the need for research on consumer or community values and preferences.

Bringing rigor to evaluations of large-scale programs to improve infant and young child feeding and nutrition: the evaluation designs for the Alive & Thrive initiative

BACKGROUND

The evidence base on the impact of large-scale infant and young child feeding (IYCF) and nutrition programs is limited, partly due to the challenges of rigorously evaluating complex programs including multiple interventions.

OBJECTIVES

To describe the process used to design Alive & Thrive's impact evaluations in the three target countries and discuss the feasibility of developing contextually relevant designs adapted to the country-specific programmatic context.

METHODS

The evaluation designs for Alive & Thrive needed to address several challenges. These included the selection of intervention components to evaluate rigorously; the identification of appropriate comparison groups in the context of rapidly scaling-up programs; the choice of impact indicators; addressing measurement challenges related to evaluating the impact of interventions targeted during the first 2 years of life on stunting; and developing methods and tools to assess implementation, utilization, and program impact pathways within evolving program portfolios.

RESULTS

In Bangladesh and Vietnam, cluster-randomized probability designs are used for the impact evaluations; in Ethiopia, the impact evaluation uses an adequacy design. In all three countries, repeated cross-sectional surveys, 4 years apart, are used to measure impact, and appropriate age groups are sampled separately to capture change in the main impact indicators. In addition, theory-driven process evaluations are used to study factors that facilitate or prevent achievement of impact and scale.

CONCLUSIONS

We conclude that robust impact and process evaluations of complex, large-scale nutrition programs are feasible, but that early implementer-evaluator engagement and shared vision and motivation to establishing meaningful evaluations are essential.

Physical growth and development of the malnourished child: contributions from 50 years of research at INCAP

This paper reviews the main findings and policy implications of 50 years (1949-1999) of research conducted by INCAP on growth and development. Topical areas reviewed include a) maternal size and birthweight and the causes of intrauterine growth retardation (IUGR), b) patterns and causes of postnatal growth retardation, c) the relative importance of genetics and the environment in explaining differences in growth among populations, d) the implications of being small, for both children and adults, e) bone growth and maturation and dental development, f) menarche, and g) methodological contributions such as anthropometric reference data, quality control of data collection, development of risk indicators and use of anthropometry in nutrition surveillance systems. Key contributions to knowledge by INCAP include a) characterization of growth failure and maturational delays as mainly occurring during the intrauterine period and the first 3 years of life b) clarification of the role of small maternal size and of inadequate dietary intakes during pregnancy as major causes of intrauterine growth failure, c) evidence that diarrheal diseases and poor dietary intakes are the principal causes of growth failure in early childhood, d) demonstration that environmental factors related to poverty, and not genetic or racial ancestry, account for most of the differences in growth between populations, e) evidence that growth failure predicts functional impairment in the child as well as in the adult andf) demonstration that nutrition interventions are effective in preventing growth failure and its consequences, if targeted to needy women and young children. INCAP's work has contributed knowledge that has informed and improved policies and programs aimed at overcoming maternal and child undernutrition and promoting optimal growth and development.

Maternal supplementation differentially affects the mother and newborn

Although studying the effect of supplementation on maternal health or the outcome of pregnancy was not a primary goal of the Institute of Nutrition of Central America and Panama Oriente Longitudinal Study, many important findings in these areas were produced. As part of the study, a food supplementation program was implemented. Two villages received Atole, a gruel containing protein and energy, and 2 matched villages received a refreshing, low-energy drink containing no protein. Both drinks contained micronutrients. Some women did not choose to consume the supplements and those who did consumed widely varying amounts. More volume of Fresco was consumed than Atole. The energy in the supplements improved birthweight, with no apparent additional benefit from protein or micronutrients. Researchers identified several groups of women who benefited from supplementation more than others by having babies with higher birthweights, including those with poorer current nutritional status and those who consumed high amounts of the supplement continuously from one pregnancy to the next. Results from the study provided an early indication that supplementation might increase the duration of gestation and, thus, reduce preterm birth. On the other hand, maternal supplementation did not substantially alter the duration of postpartum amenorrhea once concurrent infant supplementation was taken into account. Finally, findings from this study provided evidence of a biological trade-off between maintenance of maternal nutritional status and increasing fetal size that was responsive to both current maternal nutritional status and supplement intake but not to the mother's nutritional status earlier in life.

The Oriente Study: program and policy impacts

This journal supplement summarizes the many contributions of the Oriente Study to scientific knowledge. This article asks whether this knowledge has actually translated into program and/or policy changes. It describes 2 key areas where this is the case: 1) in defining the "window of opportunity" for nutrition interventions and changing policy regarding the targeting of nutrition interventions; and 2) in building the economic argument for investing in early childhood nutrition. It concludes that the study contributed most of the research evidence supporting the change in policy adopted by the U.S. government in 2009, which encourages the targeting of food-assisted maternal and child health and nutrition programs to pregnant mothers and children under 2 y of age. The paper reviews the process and the complementary evidence that led to this policy change. The Oriente Study also provides the first direct, and the strongest, evidence supporting the economic argument in favor of investing in early child nutrition. The results show a direct link between improved nutrition in early childhood and persistent benefits in adult physical status, schooling, cognitive skills, and economic productivity. It is hoped that, given the multiple shocks currently affecting the poor, these powerful results will help stimulate greater investments in maternal and child nutrition in the short term.

Growth and micronutrient status in children receiving a fortified complementary food

Linear growth retardation and anemia are the most prevalent nutritional problems in the world; effective interventions are urgently needed. We evaluated Ecuador's National Food Nutrition Program (PANN 2000) that included a micronutrient-fortified complementary food (FCF), Mi Papilla, in poor periurban and rural communities of Ecuador. The program is preventive and targeted to all infants and young children living in poor communities and receiving government health services. We compared dietary intake, micronutrient status, and growth over 11 mo in a cohort of children from the catchment areas of the PANN 2000 with same-age control children in nearby communities eligible to enter the program 1 y later. PANN 2000 children enrolled in the program when they were age 9-14 mo and were age 20-25 mo at the final survey. They consumed significantly more energy, protein, fat, iron, zinc, vitamin A, and calcium than control children because of their FCF consumption. Anemia, 76% in both groups at baseline, fell to 27% in PANN 2000 children but only to 44% in control children (P < 0.001). The odds of being anemic were 58% lower for PANN 2000 children (P = 0.003). The effects on linear growth and weight were limited to children who were older when the program began (12-14 mo) and were significant for weight (interaction with age, 0.38 kg; P = 0.029) and positive but not significant for length (0.66 cm; P = 0.08). An FCF, including ferrous sulfate, delivered through public health services, is highly effective in improving weight and hemoglobin and reducing anemia.

Determinants of nutrition improvement in a large-scale urban project: a follow-up study of children participating in the Senegal Community Nutrition Project

Objective

To study individual determinants of differential benefit from the Senegal Community Nutrition Project (CNP) by monitoring improvement in children's weight-for-age index (WA) or underweight status (WA  < –2 Z-scores) during participation.

Design

A follow-up study using the CNP child monitoring data. Linear general models compared variations in WA according to 14 factors describing the beneficiaries and CNP services.

Setting

Poor neighbourhoods of Diourbel, a large city in Senegal, West Africa. Over a 6-month period, the CNP provided underweight or nutritionally at-risk 6–35-month-old children with monthly growth monitoring and promotion and weekly food supplementation, provided that mothers attended weekly nutrition education sessions.

Subjects

All the children who participated in the first two years of the project (n = 4084).

Results

Mean WA varied from − 2.13 (standard deviation (SD) 0.82) to − 1.58 (SD 0.81) Z-scores between recruitment and the end of the follow-up. The lower the child's initial WA, the greater was their increase in WA but the lower was the probability of recovery from underweight. Only 61% of underweight children recovered. Six months of CNP services may not be sufficient for catch-up growth of severely underweight children. The number of food supplement rations received was not a direct indicator of the probability of recovery. After adjustment for services received and initial WA, probability of recovery was lower in girls, in younger children, in twins and when mothers belonged to a specific ethnic group.

Conclusions

Determinants of benefit from CNP differed from the risk factors for underweight. Identification of participants with a lower probability of recovery can help improve outcome. Moreover, an explanation for the lack of recovery could be that many underweight children are stunted but not necessarily wasted.

Determinants of nutrition improvement in a large-scale urban project: a follow-up study of children participating in the Senegal Community Nutrition Project

OBJECTIVE

To study individual determinants of differential benefit from the Senegal Community Nutrition Project (CNP) by monitoring improvement in children's weight-for-age index (WA) or underweight status (WA < -2 Z-scores) during participation.

DESIGN

A follow-up study using the CNP child monitoring data. Linear general models compared variations in WA according to 14 factors describing the beneficiaries and CNP services.

SETTING

Poor neighbourhoods of Diourbel, a large city in Senegal, West Africa. Over a 6-month period, the CNP provided underweight or nutritionally at-risk 6-35-month-old children with monthly growth monitoring and promotion and weekly food supplementation, provided that mothers attended weekly nutrition education sessions.

SUBJECTS

All the children who participated in the first two years of the project (n=4084).

RESULTS

Mean WA varied from -2.13 (standard deviation (SD) 0.82) to -1.58 (SD 0.81) Z-scores between recruitment and the end of the follow-up. The lower the child's initial WA, the greater was their increase in WA but the lower was the probability of recovery from underweight. Only 61% of underweight children recovered. Six months of CNP services may not be sufficient for catch-up growth of severely underweight children. The number of food supplement rations received was not a direct indicator of the probability of recovery. After adjustment for services received and initial WA, probability of recovery was lower in girls, in younger children, in twins and when mothers belonged to a specific ethnic group.

CONCLUSIONS

Determinants of benefit from CNP differed from the risk factors for underweight. Identification of participants with a lower probability of recovery can help improve outcome. Moreover, an explanation for the lack of recovery could be that many underweight children are stunted but not necessarily wasted.

Programme and policy issues related to promoting positive early nutritional influences to prevent obesity, diabetes and cardiovascular disease in later life: a developing countries view

Public health policy differs from programme insofar as the former is the expression of goals at a higher decision-making level (international, regional, national or provincial) and the latter involves the execution of intervention measures at the community or individual level. It has recently become fashionable to speak of "evidence-based" policy. There is now ample evidence to suggest that early nutritional influences on chronic disease risk in later life are contributing to the acceleration of the overall worldwide epidemic of obesity and non-transmissible diseases. In developing countries, in which 80% of the world's population resides, the opportunities for preventive policy must be balanced against needs, cost and effectiveness considerations and the intrinsic limitations of policy execution. Not everyone in the population is at risk of suffering from any given negative condition of interest, nor will everyone at risk benefit from any given intervention. Hence, decisions must be made between universal or targeted policies, seeking maximal cost-efficiency, but without sowing the seeds of either discrimination or stigmatization with a non-universal application of benefits. Moreover, although large segments of the covered population may benefit from a public health measure, it may produce adverse and harmful effects on another segment. It is ethically incumbent on policy makers to minimize unintended consequences of public health measures. With respect to the particular case of mothers, fetuses and infants and long-term health, only a limited number of processes are amenable to intervention measures that could be codified in policy and executed as programmes.

Predictors of improvement in hemoglobin concentration among toddlers enrolled in the Massachusetts WIC Program

OBJECTIVE

Nutrition supplementation programs are generally targeted to those members of the population who are thought to be at risk of an undesirable outcome, but not all who participate in such programs respond to them. We sought to identify determinants of improvement in hemoglobin concentration among young children in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC).

DESIGN

We conducted an observational study using data from 9,930 children who were enrolled in the Massachusetts WIC program and had data available on their hemoglobin values at both 1 and 2 years of age. Predictors of change in hemoglobin concentration between these ages were studied using multivariate statistical modeling.

RESULTS

Overall, hemoglobin concentrations increased from age 1 to 2 years in those who had been breastfed 25 or more weeks (P < .0001) and were female (P < .01), and decreased with increasing weight at 1 year of age (P < .001). The determinants of change in hemoglobin concentration differed from the determinants of hemoglobin concentration at age 1 year.

CONCLUSIONS

The analytical approach used here could be extended to identify subgroups of WIC participants likely to improve in other outcomes. If current efforts to increase the duration of breastfeeding among WIC participants are successful, the importance of WIC in improving hemoglobin concentration among young children also will increase.

Discussion: Targeting is making trade-offs

The previous articles presented different aspects of targeting: the implicit political implications, the trade-offs in giving power to different stakeholders to decide and to implement targeting, perceptions of frontline workers in implementing a program, and a technical article about selecting a scale for targeting, which we review in greater detail. It is well recognized that targeting results in a trade-off between not serving those who should be served and including those who should not be served. Less well recognized are the trade-offs that are the consequences of deciding between using indicators of risk vs. using indicators that predict benefit.

Food consumed does not account for the higher prevalence of obesity among stunted adults in a very-low-income population in the Northeast of Brazil (Maceió, Alagoas)

OBJECTIVE

To study the food pattern of stunted and nonstunted, obese and nonobese individuals in a very-low-income population.

DESIGN

A household survey.

SETTING

Slum set up by the 'Homeless Movement', city of Maceió (Alagoas), Brazil.

SUBJECTS AND METHODS

A total of 532 adults classified by sex, stature (Z</= and Z > -2s.d. of the NCHS curves), and body mass index (BMI) were compared using the following variables: waist circumference, waist-hip circumference ratio (W/H), percentage body fat (skinfold thickness and bioelectrical impedance), and food intake (24-h recall).

RESULTS

The prevalence of stunting was 22.6%. In all, 30% of the stunted subjects were overweight or obese, compared with 23% for the nonstunted individuals (P<0.05). In women, logistic regression analysis showed a strong association among weight, abdominal fat, and stunting (r=0.81). No significant differences were observed in the values of W/H or in the qualitative menu of the different categories. Energy intake was below the RDA figures (about 63%). There was similarity among the groups regarding the proportion of macronutrients, except for the fact that stunted obese women ingested less fat and protein than nonstunted obese women. Stunted obese individuals consumed less energy (5962 kJ) than the population as a whole (6213 kJ), an amount far lower than their average needs, which were calculated on the basis of their shorter stature (8109 kJ).

CONCLUSION

The observed energy consumption seems compatible with the panorama of undernutrition present in the population, but it does not explain the high prevalence of obesity detected.

Interrelationships between power-related and belief-related factors determine nutrition in populations

The vast majority of social research in nutrition has focused either on economic, material and political factors ("power-related" variables) or on psychological, cultural and attitudinal factors ("belief-related" variables). Even when data on both classes of factors are collected, the orientation in analysis is to treat one of the two classes as "confounding" or "control" variables. Although single-focus studies have yielded essential knowledge about the role of specific factors, they fail to reveal the mechanisms through which belief-related and power-related variables interact to produce nutritional outcomes. Data from the Nutrition CRSP project in Mexico are used to illustrate the interactions between household economic conditions and maternal education on household diet. As has been seen in other developing country contexts, women in more favorable economic circumstances, and who have more education, tend to feed their children a higher quality diet. However, even in better-off households dietary quality is not uniformly high, a finding that reflects the operation of other values and cultural factors that direct resource allocation to other sectors of family activity.

School height censuses are reliable and valid tools for small-area targeting of nutrition interventions in Honduras

Nutrition program planners often need information on the relative burden of malnutrition in different communities, or administrative units, to decide where best to invest limited available resources. National nutrition surveys, however, rarely provide precise, representative findings at a finer level than that of large, subnational regions. The school height census is an alternative, low-cost approach that does provide disaggregated data on growth retardation at the local level. This study assessed the reliability and validity of the school height census for small-area targeting of nutrition interventions in Honduras. Reliability was assessed by examining the stability of small-area estimates of mean height-for-age Z-score over five consecutive years from 1993 to 1997. Validity was assessed by comparing municipality-level mean height-for-age Z-score in the 2001 school height census with the same parameter estimated in an anthropometric survey of children < 5 y old conducted in representative samples in 70 municipalities 3-7 mo earlier. The study found that stable estimates of mean height-for-age Z-score could be obtained at the level of municipalities or larger (intraclass correlation coefficients > or = 0.85). The school height census estimates of mean height-for-age Z-score at the municipality level were also valid, with the reference criterion the survey results for children > or = 1 y of age (Spearman's rank correlation = 0.74). School height censuses cannot provide reliable estimates of levels of growth retardation in individual schools. Wider use of school height censuses could make it much easier to identify communities that might benefit from targeted nutrition interventions.

Understanding needs is important for assessing the impact of food assistance program participation on nutritional and health status in U.S. elderly persons

This study aimed to assess the impact of food assistance programs on nutritional and health status of nutritionally needy elderly persons. Two cross-sectional and one longitudinal data sets were used: Third National Health and Nutrition Examination Survey (1988-94), Nutrition Survey of the Elderly in New York State (1994) and Longitudinal Study of Aging (1984-1990). Multiple logistic and linear regression analyses were used to examine whether food assistance participants among food insecure elderly (i.e., those whose needs for food assistance programs are met) have better nutrient intake, skinfold thickness and self-reported health status and less nutritional risk, hospitalization and mortality than nonparticipants (i.e., those whose needs are unmet) and whether the benefit is larger than that among food secure elderly persons. Across three data sets, food insecure elderly persons had poorer nutritional and health status than food secure elderly persons. Contrary to the hypotheses, among food insecure elderly persons, food assistance participants had similar or poorer nutrient intakes, skinfold thickness, nutritional risk, self-reported health status, hospitalization and mortality than nonparticipants. Food secure participants had similar nutritional and health status as food secure nonparticipants. Lack of information on the dynamic nature and changes in needs with program participation in the three data sets likely did not allow accurate estimation of the impact of food assistance participation. Different study designs, as well as theory and knowledge of needs that clarifies need status and its change within each older individual across an appropriate time interval, are necessary to accurately assess impacts of food assistance programs.

Influence of parental height and sociodemographic factors on adolescent height in Brazil

OBJECTIVE

To analyze the influence of parental stature and environmental factors on the stature of adolescents from a national survey sample.

METHODS

A nationwide survey was carried out in 1989 among a stratified, two-stage, probability cluster sample of 14,455 Brazilian households to provide estimates of anthropometric deficits for urban and rural populations from the five regions of the country. Stature was measured for 5681 boys and girls age 14-18 years, 78.9% of their fathers, and 93.8% of their mothers. Associations between explanatory variables and adolescent height in centimeters were assessed by fitting multiple linear models to the data.

RESULTS

The predicted effects of parental stature and environmental conditions together sum to a total of 17 cm when comparing a boy born to parents with stature below the median and living in the underdeveloped rural Northeast region (1.56 m) with one born to parents with stature above the median and living in the partially industrialized urban South region (1.73 m). For girls, this estimated difference was 12 cm. For boys, the overall influence of parents' stature was 10 cm (R(2)= 0.40) and the sociodemographic factors had an overall influence of 7 cm (R(2) = 0.29). For girls, these values were 7 cm (R(2)= 0.35) for the parental influence and 5 cm (R(2) = 0.11) for the sociodemographic factors.

CONCLUSIONS

Mother's stature had the same influence on adolescent's stature as father's stature. Independent of parental stature, environmental factors have a strong influence on adolescent stature, particularly among boys.

Obesity and abdominal fatness associated with undernutrition early in life in a survey in Rio de Janeiro

BACKGROUND

Undernutrition early in life has been associated with chronic diseases and obesity among adults. Our study tested the hypothesis by examining the association between low stature, a marker of early poor nutrition, with obesity and abdominal fatness among adults.

METHODS

A population-based survey was conducted in 1996, among 2040 households, with a non-response rate of 11.2%. Weight, height, waist and hip circumference, and skinfolds were measured at home.

RESULTS

Age-adjusted prevalence of body mass index (BMI) greater than 25 kg/m2 was 32% more frequent among adult men, and 60% more frequent among adult women, comparing the first to the fourth quintile of height. A J-shaped curve describes the association between weight and the sum of skinfolds with stature after adjusting for confounding by age, energy intake, physical activity, smoking, age at menarche, and race. The adjusted odds ratio of obesity (BMI>30 kg/m2) for short stature, compared to normal stature, was 1.57 with a 95% confidence interval (CI) = 0.90-2.71 among men and 1.84 with a 95% CI=1.10-3.06 among women. Short stature was associated with the risk of abdominal fatness only among women, with an odds ratio=1.77; 95% CI=1.10-2.83.

CONCLUSIONS

Increased risk of obesity and abdominal fatness among women of short stature, a marker for undernutrition early in life, was not explained by racial and socio-economic conditions, energy intake or age at menarche.

Short stature and hypertension in the city of Rio de Janeiro, Brazil

OBJECTIVE

Stature is a powerful indicator of poor nutrition early in life in nations where undernutrition is a public health problem. Hypertension in adults has been associated with factors present early in life such as low birth weight. We tested the hypothesis that short stature is associated with hypertension among adults.

DESIGN AND SETTING

A household survey of representative adults in Rio de Janeiro city, Brazil was carried out in 1996.

SUBJECTS

Blood pressure and anthropometric measures were collected from 2802 adults in their own households. Prevalence estimates and modelling incorporated the sample design and weights.

RESULTS

Age-adjusted prevalence of hypertension for both sexes was lower in the third quartile of stature distribution. In women, but not in men, the odds ratio comparing the first quartile of stature with the fourth quartile was statistically significant with an odds ratio of 1.68 (95%CI 1.02-2.76). Adjusting for known risk factors for hypertension such as age, income, smoking, sodium and alcohol intake and race, the association among women, comparing the first with the fourth quartile for stature, was 1.84 (95%CI 1.03-3.30). With further adjustment for residual of weight on height the ratio reduced to 1.76 (95% CI 0.97-3.19, P value of trend = 0.03). Systolic blood pressure showed a U-shaped association with quartiles of stature, mainly among women, with a beta-coefficient significantly lower at the third quartile.

CONCLUSIONS

This association of stature with hypertension supports the theory of an important ontogenetic dependence of adult blood pressure, at least among women.

Twenty years of WIC: a review of some effects of the program

The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) began in 1974 after a 2-year pilot program. WIC links food assistance and nutrition education to health care for at-risk persons. The program had approximately 344,000 participants in 1975 and has grown to provide services to nearly 6 million participants. Infants born to women who participate in WIC during pregnancy tend to have a slightly higher mean birth weight than those born to women who were eligible but did not participate in WIC. Higher birth weight has been associated with a slightly higher mean gestational age. The prevalence of low birth weight and very low birth weight among infants and the prevalence of iron deficiency anemia among toddlers and preschool children is lower for those participating in WIC than for those not participating in WIC.

Impact of zinc supplementation on morbidity from diarrhea and respiratory infections among rural Guatemalan children

OBJECTIVE

A community-based, randomized, double-blind intervention trial was conducted to measure the impact of zinc supplementation on young Guatemalan children's morbidity from diarrhea and respiratory infections.

METHODS

Children aged 6 to 9 months were randomly assigned to receive 4 mL of a beverage containing 10 mg of zinc (as zinc sulfate) daily (7 d/wk) for 7 months (n = 45) or a placebo (n = 44). Morbidity data were collected daily. Diagnoses of diarrhea, fever, and anorexia were based on mothers' definitions. Respiratory infections were defined as the presence of at least two of the following symptoms: runny nose, cough, wheezing, difficulty breathing, or fever.

RESULTS

High rates of diarrhea and respiratory infections were reported. Children from the placebo group had a 20% episodic prevalence of diarrhea, with 8 episodes/100 d, and a 7% episodic prevalence of respiratory infections, with 3 episodes/100 d. The median incidence of diarrhea among children who received zinc supplementation was reduced by 22% (Wilcoxon rank test), with larger reductions among boys and among children with weight-for-length at baseline lower than the median of the sample (39% reductions in both subgroups). Zinc supplementation also produced a 67% reduction in the percentage of children who had one or more episodes of persistent diarrhea (chi2 test). No significant effects were found on the episodic prevalence of diarrhea, the number of days per episode, or the episodic prevalence or incidence of respiratory infections.

CONCLUSIONS

The large impact of zinc supplementation on diarrhea incidence suggests that young, rural Guatemalan children may be zinc deficient and that zinc supplementation may be an effective intervention to improve their health and growth.