Breast milk contains fungi which may help seed a baby's microbiome

Bacteria aren’t the only microorganisms passed from mothers to babies in breast milk – fungi are transferred too. This may play an important role in kickstarting the colony of microorganisms inside an infant’s gut, which form part of a healthy digestive system.

The excitement around the impact of breast milk on microorganisms in the gut, called the microbiota, has largely focused on bacteria, with little known about fungi. But fungi could be important to the development of allergies or disease later in life.

Maria Carmen Collado at the Institute of Agrochemistry and Food Technology in Spain and her colleagues had already found fungi in the breast milk of women in Spain. So they widened the net to include women living in South Africa, China and Finland as well.

They found fungi in the breast milk of all 80 women included in the study. The most prevalent was Malassezia, a genus of fungi found in oil-producing glands on skin and hair, followed by Davidiella, a genus of fungi also found in the vagina.

Regional differences suggest environmental factors such as diet or geography play a part in the fungal composition of breast milk, says Collado.

This is important, because mothers transfer a unique mix of  bacteria and fungi to their newborns, she says.

Saccharomyces boulardii is a fungus currently given to infants to reduce the severity of diarrhoea. Collado hopes her team’s findings could open the door to other fungi that could be used to improve infant gut health.