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Effect of iron on neonatal gut flora during the first week of life
Insights
Low iron in infant formula promotes a healthy gut microbiome. Unfortified cow's milk preparations, similar to breast milk, enhance beneficial bacteria and reduce harmful ones in newborns.
Area of Science:
- Neonatal nutrition
- Microbiome development
- Gut health
Background:
- The neonatal gut microbiome plays a crucial role in infant health.
- Dietary factors significantly influence the early colonization of the infant gut.
- Iron fortification in infant formula is a common practice, but its impact on the microbiome is not fully understood.
Purpose of the Study:
- To compare the effects of breast milk, iron-fortified cow's milk formula, and unfortified cow's milk formula on the fecal microbiome of newborns.
- To investigate the relationship between iron content in infant diet and gut bacterial colonization patterns.
Main Methods:
- Faecal specimens were collected from 23 infants within the first week of life.
- Infants were categorized into three groups based on their diet: breast milk, iron-fortified cow's milk formula, or unfortified cow's milk formula.
- Bacterial populations (Bifidobacteria, Enterobacteriaceae, Bacteroides, Clostridia) and fecal pH were analyzed.
Main Results:
- Breast milk-fed infants exhibited low fecal pH, high Bifidobacteria counts, and low counts of Enterobacteriaceae, Bacteroides, and Clostridia.
- Infants on iron-fortified formula showed high fecal pH and increased counts of Enterobacteriaceae and putrefactive bacteria, with high Bifidobacteria counts.
- Unfortified formula led to a gradual increase in Enterobacteriaceae followed by a rise in Bifidobacteria, suggesting delayed but developing colonization.
Conclusions:
- A low iron content in infant nutrition enhances resistance to neonatal gut colonization.
- Unfortified cow's milk preparations promote a gut environment more similar to that of breast-fed infants.
- Dietary iron levels are a critical factor in shaping the early-life gut microbiome.
Abstract:
Faecal specimens from 23 infants during the first week of life were compared. Ten infants received breast milk, six received cow-milk preparation supplemented with iron (+/- 5 mg/l) and seven unfortified cow-milk preparation (iron concentration less than 0.5 mg/l). Those on breast milk had low faecal pH, high counts of bifidobacteria and low counts of Enterobacteriaceae, bacteroides and clostridia. Infants receiving fortified cow-milk preparation had a high faecal pH and high counts of Enterobacteriaceae and putrefactive bacteria such as bacteroides and clostridia. Counts of bifidobacteria were also high. In those on unfortified cow-milk preparation a slow rise was observed in counts of Enterobacteriaceae followed by an increase in counts and isolation frequency of bifidobacteria: the latter was still rising on day 7. It is concluded that a low iron content in standard preparations of cow's milk enhances resistance of the neonatal gut to colonization.