Pregnancy and child

Breast milk 'raises' immunity

Breast milk is better for babies than formula because it “kick starts their immune system”,_ The Daily Telegraph_ reported.

This news story is from a small laboratory study testing a new non-invasive method for extracting genetic information from the gut cells found in infant stool samples. The researchers also wanted to compare the intestinal genetic profiles of babies that were breastfed to those of formula-fed babies.

This study did find a difference in gene activity in the cells from the guts of breastfed compared with bottle-fed babies. However, it is uncertain whether this is due to any difference between the immune systems of breastfed and bottle-fed babies. Also, the babies were not randomly assigned to receive either breast or formula milk, so it is possible that other factors could have caused these differences. Further larger studies are needed.

Breast milk is known to help protect babies against various disorders and boost their immune defences. While this study may be of scientific interest and merit, these results do not offer any new information about the relative benefits of breastfeeding.

Where did the story come from?

The study was carried out by researchers from Texas A & M University, the University of Illinois and Mead Johnson Nutrition (a manufacturer of infant formula) in Evansville, Indiana. It was funded by grants from Mead Johnson and the National Institutes of Health. It was published in the peer-reviewed American Journal of Physiology, Gastrointestinal and Liver Physiology.

The study was given some prominence in the Telegraph , but these early findings by themselves do not warrant the Telegraph ’s conclusion that breast milk is best because it “kick starts the immune system”.

What kind of research was this?

This was a small, proof-of-concept laboratory study. The researchers aimed to test a new non-invasive method for extracting genetic information about gut cells from infant stool samples. They intended to use this method, patented by one of them, to ‘fingerprint’ and compare the intestinal genetic profiles of babies that were either exclusively breast or formula fed.

Although breastfeeding is known to help protect the developing infant against a range of infections and other disorders, less is known about how it does this. The researchers report that there is some evidence from animal studies and human infants that the intestinal tract (or ‘gut’) undergoes marked structural and functional changes in response to feeding. They also say that there is evidence that components in breast milk may contribute to the way the gut matures. However, exploring whether this is the case has been difficult because of the ethical constraints around obtaining gut tissue from healthy babies for research purposes.

The infants in this study were not randomly assigned to receive either breast or formula milk, but were categorised according to what they were already being fed. The study may, therefore, be affected by confounding. This means that factors other than the type of feeding may be contributing to any differences in gene activity seen between formula-fed and breastfed babies. The researchers tried to reduce these ‘confounding effects’ by ensuring that the babies were similar in many other ways. However, it was not possible to avoid all potential confounding factors.

What did the research involve?

Researchers recruited the mothers of 22 healthy full-term infants: 12 exclusively breastfed and 10 fed only on formula. The mothers in both groups had similar average ages and number of previous children, and there was a similar number of male and female babies of similar birth lengths and weights. Most of the infants were Caucasian.

The study excluded infants who were intolerant to cows’ milk or who were receiving a mix of breast and formula milk. Infants consuming juice or solid foods were also excluded, as were babies who became clinically ill or who had antibiotic treatment. Mothers of formula-fed babies were all provided with a certain type of formula, Enfamil LIPIL, for the duration of the study.

The parents collected stool samples from their babies at three months of age, with instructions on how to do this. Samples were kept in a sterile solution, and frozen and transported to the laboratory by research staff. The parents also weighed the babies before and after each feeding for 24 hours before the stool sample was taken and the change in body weight was used as an estimate of breast-milk or formula intake. Maternal age and infant birth weight and length were also recorded.

The researchers used a technique to isolate any intestinal cells in the stool samples and analysed the genetic material from these in the laboratory. The activity of certain genes was then compared between the groups.

What were the basic results?

The researchers were able to identify several gene sets or combinations showing different levels of activity in the formula- or breastfed infants. They say that their non-invasive technique for isolating genetic material from the developing infant gut was successful.

There was also some variability in gene activity among breastfed infants. The researchers say this could be explained by variations in breast-milk composition.

How did the researchers interpret the results?

The researchers say these findings support the theory that genetic material isolated from babies’ stools can be used to help understand the development of the intestine and the effect of different types of nutrition. Nutrition is believed to play a major role in the way the infant gut develops and is particularly crucial during the early postnatal period, having an impact not only on immunity, but also digestion, absorption and colonisation by different types of bacteria.
They say their study indicates for the first time that gene expression in infants fed breast milk is different from gene expression in formula-fed infants.


This study found that genetic material from the infant intestine can be isolated from stool samples. The researchers say that analysis of this genetic material suggests that the genetic pathways of breastfed infants differ from those found in infants fed formula milk.

The results of this small study could be of great interest to other scientists in the field. Its main purpose appears to have been to test the practicality and usefulness of a new method for examining cells from babies’ guts. However, it does not, by itself, tell us anything new about the practical health benefits of breastfeeding compared to formula feeding.

In terms of investigating the effects of breastfeeding compared to bottle-feeding, the infants were not randomly assigned to either type of feeding, so the study may be affected by confounding. This means that differences between the babies other than the type of feeding may be contributing to any differences in gene activity seen. The researchers did try to ensure that the babies in the groups were similar in some areas, but other factors could still be having an effect. For example, the researchers did not test exactly which cells the genetic material was coming from, and this could have differed between infants.

It has been established that breast milk helps protect babies against various disorders and boosts their immune defences at a time when their immune system is still developing.

The technique is likely to need further development, and the results of this study will need replication in larger, more comprehensive studies.

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