Broad - to examine the result of feeding RS to 3-5 year old rural Malawian children on zinc homeostasis and environmental enteropathy (EE).

Specific -

1. To measure zinc status using a dual zinc stable isotope assay before and after administering resistant starch (RS) in 20 children.
2. To measure intestinal function using a site-specific sugar absorption test before and after administering RS in 20 children.
3. To determine the relationship between RS and zinc homeostasis.
4. To determine the relationship between RS and environmental enteropathy.

A total of 20 (10 M, 10 F) stunted rural Malawian children aged 36-60 months will be studied to determine if there is an effect of feeding RS on zinc homeostasis and environmental enteropathy. These children are at high risk for zinc deficiency and environmental enteropathy by their demographic characteristics. Children will first have a quantitative assessment of zinc homeostasis where each child is given 2 zinc stable isotopes, one by mouth and another intravenously, which is followed by a stool and urine collection of 4 days. Zinc isotopes are quantified in the feces and urine, and these values are used to calculate the primary outcome, net zinc balance. This is followed by an assessment of environmental enteropathy quantitatively measured using the non-invasive site specific sugar absorption test, where each child drinks 100 mL of a sugar solution and a urine collection follows. The quantities of non-metabolizable sugars are measured, and the ratio of two of the sugars, lactulose and mannitol, is a measure of environmental enteropathy. Then the children will receive a dietary supplement, corn starch that has been modified to reduce its dietary absorption, for 5 weeks, which they will add to their phala. The RS is a standard food product that has been used safely in many millions of people for several decades. After taking this RS for 4 weeks both the zinc stable isotope test and the dual sugar absorption test will be repeated on the children to see if they have improved. These results will offer preliminary data as to whether RS might be used effectively on a large scale in the community to alleviate zinc deficiency and/or environmental enteropathy.

Inclusion Criteria:

• Any stunted, otherwise healthy child aged 36-60 months living close to the Chipalonga Health Center. Stunting will be defined as height-for-age Z-score (HAZ) < -2. Children will be selected on the basis of having the lowest weight-for-height Z-scores (WHZ), and by dietary surveys on which their caretakers report consuming animal source foods < twice per month. Previous field work indicates about 80% of children are stunted and almost all children consume animal source foods < twice per month.

Exclusion Criteria:

• Children who are not permanent residents in the village. Additionally, children with severe chronic illness such as cerebral palsy, and those who are receiving other supplementary food, or those who are participating in another research study are all ineligible to participate.