The urinary excretion of lactulose (L) and Mannitol (M) is a measure of the indemnity of the intestinal mucosa. To evaluate changes in permeability during the first year of life 111 infants of the low socio-economic stratum with samples at one month, at 3-4 months and at 10-12months of age; 38 of them were studied longitudinally. One hundred mg/kg of each sugar were ingested dissolved in water, urine was collected for 5 hours and sugars were measured by gas chromatography. Intestinal premeability was also measured in these infants during episodes of diarrhea (n=28). Table

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No changes in L and M were detected during the first year of life; however, during diarrhea changes in the L/M ratio were observed, suggesting that the condition induces changes in mucosal integrity-This non-invasive test is the best tool for evaluation of mucosal damage.