The bacteria challenge: how infants are better protected
A Danish-Sino team of researchers has discovered that infants are at a lower risk of developing allergic disease at an older age when they encounter various bacteria during their pea-size period. Presented in the Journal of Allergy and Clinical Immunology, the findings suggest that novel factors are influencing modern lifestyle diseases.
Allergies, what experts call oversensitivity disease, impact around a quarter of the Danish population. The number of cases keeps rising. This latest study sheds new light on why bacteria could prove beneficial during infancy.
Scientists led by the University of Copenhagen in Denmark say these various bacteria offer protection. 'In our study of over 400 children we observed a direct link between the number of different bacteria in their rectums and the risk of development of allergic disease later in life,' says Hans Bisgaard, consultant at Gentofte Hospital, head of Copenhagen Studies on Asthma in Childhood (COPSAC), and professor of children's diseases at the Faculty of Health Sciences, University of Copenhagen.
'Reduced diversity of the intestinal microbiota during infancy was associated with increased risk of allergic disease at school age,' Professor Bisgaard says. However, the greater the diversity, the greater the chances that risk is mitigated, and the greater the variation, the lower the risk.
'So it makes a difference if the baby is born vaginally, encountering the first bacteria from its mother's rectum, or by caesarean section, which exposes the new-born baby to a completely different, reduced variety of bacteria. This may be why far more children born by caesarean section develop allergies.'
Before he or she is born and up to six months after emerging into this world, an infant is protected by the mother's immune system. So bacterial flora can be affected by any antibiotics ingested by the mother, as well as by any artificial substances she has been exposed to.
'I must emphasise that there is not one single allergy bacteria,' Professor Bisgaard explains. 'We have studied staphylococci and coli bacteria thoroughly, and there is no relation. What matters is to encounter a large number of different bacteria early in life when the immune system is developing and "learning". The window during which the infant is immunologically immature and can be influenced by bacteria is brief, and closes a few months after birth.'
The results of the study are in line with the extensive number of discoveries the researchers have made in the fields of asthma and hay fever, according to the professor.
'Our new findings match the large number of discoveries we have also made in the fields of asthma and hay fever,' Professor Bisgaard explains. Like allergies, they are triggered by various factors early in life, he says.
The COPSAC group has published articles at regular intervals that offer newly discovered knowledge about allergy and asthma.
As strange as it may seem, bacteria could prove to be a fundamental part of a healthy life, according to Professor Bisgaard. Other couplings, like diabetes with intestinal flora, may exist.
'I think that a mechanism that affects the immune system will affect more than just allergies,' the Danish researchers says. 'It would surprise me if diseases such as obesity and diabetes are not also laid down very early in life and depend on how our immune defences are primed by encountering the bacterial cultures surrounding us.'
Researchers from the Statens Serum Institut in Denmark and Peking University First Hospital in China contributed to the study.