Growth faltering in infancy establishes a trajectory for lifelong health of the individual and population. Stunted growth is due to the combined effect inadequate diet (malnutrition) and infection that affects the gut mucosal lining, with increased nutrient loss due to maldigestion and malabsorption, and increased nutritional requirements due to inflammation. Intestinal integrity in infants has been improved through supplementation with vitamin A and Zinc. Iron deficiency anemia may impair intestinal integrity. This study investigates the effects of complementary fortified food on gut integrity and systemic inflammation among Zambian infants age 6-18months. Infants of 6 months +/- 2 weeks old were randomised to either 50g/day richly fortified porridge mix or 50g basal porridge mix fortified with micronutrient levels planned for maize fortification in Zambia. At 18 months, the richly fortified porridge group had a significantly higher mean lactulose to mannitol ratio than the basal-fortified group, indicating they had significantly higher intestinal permeability. This effect was not modified by child’s sex, maternal HIV status, concurrent breast-feeding or baseline anaemia. The biological significance of this increase in intestinal permeability is questionable, however further research is warranted to understand the effect of iron supplementation on gut permeability in infants with normal iron status. In conclusion, a richly fortified complementary/replacement food did not benefit and may have worsened intestinal permeability. Further investigation into local interactions of key micronutrients with gut integrity, particularly in micronutrient-replete infants is needed.