High faecal calprotectin levels in healthy, exclusively breast-fed infants

Background: Faecal calprotectin has been proposed as a sensitive marker for gastrointestinal inflammation in children and adults. High levels have been reported in healthy newborns and during the first months of life; the effect of the kind of feeding on the calprotectin concentration in stools is controversial.

Objective: To evaluate faecal calprotectin values in healthy, exclusively breast-fed (BF) or formula-fed (FF) infants.

Methods: Stool samples were obtained from 74 healthy infants (39 exclusively BF and 35 exclusively FF) with a median age of 51 days (range 13-90). Exclusion criteria were acute infections and treatment with anti-inflammatory drugs. Stool samples were stored at -20 degrees C until they were analysed, and the faecal calprotectin concentration was detected using a commercial quantitative enzyme-linked immunoassay (Calprest; Eurospital SpA, Trieste, Italy).

Results: The median faecal calprotectin concentration was significantly higher in BF infants (555.00 microg/g, range 122.5-2,000.0 microg/g) than in FF ones (206.60 mug/g, range 31.2-797.6 microg/g) (p < 0.001). We observed a significantly higher median stool frequency in BF infants than in FF ones (p < 0.001), but multiple regression analysis (independent variables: kind of feeding and stool frequency; dependent variable: calprotectin) showed a significant coefficient for the kind of feeding, but not for stool frequency (p = 0.937).

Conclusions: Our findings show that the kind of feeding influences the faecal calprotectin concentration, with higher values in healthy exclusively BF infants than in FF ones. Our study does not allow us to clearly identify the reason for our finding; this could be due to hormones (such as ghrelin and leptin), cytokines and other immunostimulating and growth factors (such as epidermal growth factor and granulocyte colony-stimulating factor) in human milk, which contribute to the development of the gastrointestinal immune system. Further investigations are needed to better clarify the mechanism underlying the relationship between feeding and faecal calprotectin levels in young infants.