Giving antibiotics to infants who are breastfeeding diminishes the beneficial effects of this food source and alters the infant's intestinal microbiota, researchers from Finland report.
"The findings support current recommendations to continue breastfeeding at least through the first year of the child, and to avoid unnecessary antibiotics," Dr Katri E. Korpela, from the University of Helsinki, told Reuters Health by email.
Breastfeeding protects against infections in early life, and long duration of breastfeeding has been associated with a reduced risk of overweight in children. These benefits are likely related to the early development of the intestinal microbiota.
Dr Korpela's team used data from 226 children who participated in a probiotic trial to investigate whether early-life antibiotic use in children prevents the beneficial long-term effects of breastfeeding on weight development and lifetime antibiotic use and whether the duration of breastfeeding is associated with long-term microbiota development.
The children in the study ranged in age from 2 to 6 years; the average age was 55 months. Half had no antibiotic use before weaning, while half had early-life antibiotic use, according to the June 13 JAMA Pediatrics online report.
Each month of breastfeeding was associated with a 6% reduction in the number of antibiotic courses (i.e., bacterial infections) during the first year of life.
Among children with no early-life antibiotic use, each month of breastfeeding was associated with a 5% reduction in lifetime antibiotic use. In contrast, there was no such relationship among children who had received antibiotics before weaning.
Children who did not receive antibiotics during early life realized a 0.08-unit reduction in body mass index (BMI) z scores for each month of breastfeeding (p<0.001), whereas children who received antibiotics during early life showed no association between breastfeeding duration and BMI z scores.
"We found that the weight-increasing effect of early-life antibiotic use overshadows the protection against overweight endowed by long breastfeeding," the investigators say. "This may explain some of the inconsistent results regarding the protection against overweight in previous large studies where antibiotic use was not analyzed."
Intestinal microbiota showed significant changes between children, with longer breastfeeding duration and no antibiotic use being associated with a more favorable profile (e.g., higher relative abundance of Actinobacteria to Firmicutes) than was longer breastfeeding duration and early-life antibiotic use.
The major drivers of interindividual difference in microbiota composition were early-life antibiotic use and duration of breastfeeding, the researchers note.
"The infant's intestinal microbiome is vulnerable to antibiotic disturbance and is likely to influence the development of the child," Dr Korpela concluded. "The results demonstrate that antibiotics should be given to infants only when necessary and their potentially harmful long-term effects on the child should be considered."
Dr Pietro Vajro, from the University of Salerno, Baronissi-Salerno, Italy, who coauthored an accompanying editorial, told Reuters Health by email, "The main implication is that early use of antibiotics modifies unfavorably intestinal microflora and that this effect may have lifetime consequences, even in those babies who received an appropriate, healthy, long-duration breastfeeding."
"The use of antibiotics in early life should be more judicious," Dr Vajro concluded. "Long duration of breastfeeding should be encouraged for its proven beneficial systemic effects and on the intestinal microbiota composition. Keeping the latter in good shape helps for the prevention of obesity and of other gut-body systems axis dysfunction based systemic diseases as well."
The Academy of Finland and Tekes partially supported this research. The authors reported no disclosures.