Zinc has been shown to enhance intestinal mucosal repair in patients suffering from acrodermatitis enteropathica; but the impact on mucosal integrity during acute (AD) or persistent (PD) diarrhoea is unknown. One hundred eleven children with AD and 190 with PD aged between 3 and 24 months received, randomly and blind to the investigators, either an elemental zinc supplement of 5 mg/kg body wt/day or placebo in multivitamin syrup for 2 weeks while intestinal permeability and, biochemical and anthropometric markers were serially monitored. The permeability test was administered as an oral dose of 5 g lactulose/l g mannitol in a 20-ml solution followed by a 5-h urine collection. The ratio of the urinary probe sugars was correlated to clinical, biochemical, and microbiological parameters. At presentation, lactulose excretion was increased and mannitol excretion decreased in both AD and PD as compared with age-matched asymptomatic children. The lactulose/mannitol ratio (L/M) was higher in subjects with mucosal invasive pathogens (rotavirus and enteropathogenic Escherichia coli) compared with children excreting Vibrio cholera and enterotoxigenic E. coli. Two-week zinc supplementation significantly reduced lactulose excretion in both AD and PD, whereas the change in mannitol excretion and L/M was similar between study groups in both studies. Changes in lactulose excretion were significantly influenced by zinc supplementation in children with E. coli, Shigella sp., and Campylobacter jejuni stool isolates. The greatest reduction in total lactulose excretion was seen in supplemented children who on presentation were lighter (wt/age less than 80%), thinner (wt/ht less than 85%), and undernourished [middle upper arm circumference (MUAC) less than 12.5 cm] or with hypozincaemia (less than 14 mumol/L).(ABSTRACT TRUNCATED AT 250 WORDS)