Premastication—Review of an Infant Feeding Practice and Its Potential Impact on Allergy and Microbiome Development

Premastication, or pre-chewing, of food as a feeding practice for infants has been practiced across cultures as an ancient evolutionary method. Whilst literature on the topic remains slim, the majority of existing research has highlighted the potential risks, such as transmission of infections. Although the concerns are valid, potential beneficial aspects have, until now, received less attention. These benefits are hypothesised to include exposure to a healthy, balanced oral microbiome, in combination with the anti-inflammatory properties of saliva and the pre-digestion of food by salivary enzymes. The hypothesis is supported by various studies that have shown the importance of early exposure to microbes for the development of the child's immune system. Moreover, a more varied microbiome earlier on in life is assumed to reduce the development of atopic diseases. Provided that the person chewing and its receiver/the child are healthy, premastication could offer a simple, well-rehearsed method to shape the child's immune system with health-promoting effects particularly in regard to primary allergy prevention. The interactive benefits of transferring an immune-stimulating pre-digested soft food portion containing small amounts of (diverse) food proteins via the oral route could be a valuable contribution to oral tolerance development in the decisive period of microbial-driven immune system maturation. This review aims to evaluate the risks but especially the potential benefits of premastication, by focussing on its possible implications in (food) allergy prevention and oral tolerance development.