Probiotic food may have varying effects on infants

The intake of beneficial microbes like yeast in the form of probiotic food supplements can have different effects on the immune systems of male and female piglets, according to a study that suggested the findings may also apply to human infants.

The researchers, including those from the University of Bristol in the UK, said piglets are valuable preclinical models for children in nutritional studies.

The study, published in the journal Frontiers in Immunology, revealed that 28-day old piglets produced very different levels of immune cells, antibodies, and other immune-associated molecules depending on their sex.

They said around 70 percent of the immune system is in the gut where its development is driven during early life, largely by the resident gut bacteria, contradicting previous evidence that the difference in immunity begins during puberty.

The study also noted that dietary supplements boosting the functions of beneficial gut bacteria work differently in male and female piglets.

According to scientists, the effect of these nutritional interventions can be masked if males and females were looked at all together.

Citing an example, the researchers said, the prebiotic inulin significantly increased the number of cells responsible for controlling immune responses such as the regulatory T-cells, in male guts but not in female guts.

"Correct development of the immune system is essential in ensuring it responds appropriately to both harmful and harmless stimulation throughout life and this development, even during the first days of life, depends on your sex," said study co-author Marie Lewis from the University of Reading in the UK.

"Although we don't know why we know that young girls tend to produce a more protective immune response to vaccination than boys. But what we did not expect to find is that young girls also appear to have a more regulated immune environment in their intestinal tissues than boys," Lewis added.

The researchers said, currently, methods analyzing the effectiveness of dietary supplements on the immune system assume that the same thing happens in boys and girls.

They cautioned that this may not be the case, and that sex may be influencing data on the effectiveness of probiotics and prebiotics in infanthood.

"The work raises some really important questions about why this happens - is it because the levels of the different sex hormones make the immune systems different almost as a side effect, even at this age, or is it because the immune and reproductive systems need to be fundamentally linked during early development," said study co-author Mick Bailey from the University of Bristol.

The researchers said the findings point to the need for designing different treatments for immune disorders in girls and boys.

"Given the underlying differences in immune development we identified between boys and girls, taking sex into account could provide a simple means to improve the effectiveness of pharmaceutics and other therapies which act on the immune system," Lewis said.