Much has been learned in recent years about the mechanisms by which breastfeeding improves child health and survival. However, there has been little progress in using these insights to improve pediatric care. Factors that are important for protecting the breast fed infant might be expected to decrease the adverse effects of weaning on diarrhea, growth, and development. The proposed study is meant to begin addressing this important gap by a clinical trial of lactoferrin supplementation in previously weaned children. Lactoferrin,an iron-binding protein with multiple physiological functions (anti-microbial, anti-inflammatory, and immunomodulatory), is one of the most important proteins present in mammalian milk. Our hypothesis is that lactoferrin (given as a daily supplement in amounts similar to those consumed if the child were still breastfed) will improve health by mimicking its protective roles in milk. The significance of these studies is that they will prove feasibility of improving child health after the end of breastfeeding by continuing ingestion of a major protective milk protein. Diarrhea and malnutrition after weaning is a global problem that may be amenable to this approach.

The proposed community-based study will be conducted in a previously weaned population at risk for repeated intestinal infections. Infants who are 12-18 months of age living in the District of Independencia, Lima, Peru will be eligible for enrollment. We will conduct a randomized double blind placebo controlled trial comparing twice daily supplementation with bovine lactoferrin versus a placebo (maltodextrin) Therapy will be continued for 6 months with close monitoring of all study participants for diarrhea and growth.

Specific aim 1: Determine the effect of bovine lactoferrin supplementation on prevention of diarrhea,measured by the number of episodes of diarrhea during a 6 month trial in previously weaned Peruvian children enrolled at 12 to 18 months of age.

Specific aim 2: Determine the effect of bovine lactoferrin supplementation on growth.

Inclusion Criteria:

1. Infants 12 to 18 months of age from the Outpatient clinics (Puestos de Salud) of Districto de Independencia in Lima, Peru will be eligible for enrollment in this study.
2. Infants previously weaned for at least one week will be eligible for study.

Exclusion Criteria:

1. Infants with either exclusive or partial breast-feeding will not be enrolled; mothers will be encouraged to continue breastfeeding.
2. Infants ill with severe, persistent or chronic diarrhea will be excluded.
3. Infants with severe malnutrition (defined as weight-for-height < -3 SDs, height-for-age < -3SDs)will be excluded.
4. Infants with a serious infections that required hospitalization 1 month prior (e.g. meningitis,pneumonia, bacteremia) will be excluded.
5. Infants with known HIV (data from parent or medical records) will be excluded.
6. Infants with underlying chronic illness (e.g. malignancy, immunosuppression, chronic renal failure, congestive heart failure, liver failure) will be excluded.
7. Infants with history of allergy to cow's milk or infant formula, eczema, allergic rhinitis or asthma will be excluded.
8. Infants with a family history of eczema, allergic rhinitis, asthma, or milk intolerance will be excluded.