Table 1.

Evidence on factors influencing the composition of human milk oligosaccharides (HMOs) and milk microbiota and their association with pediatric asthma.

Milk components	Influenced by	Impact on gut microbiota	Association with asthma
Human milk oligosaccharides	Host genetics (23, 24) Geography (24, 25) Season (26, 27) Parity (26) Lactation stage (28) Birth mode (29)	Influence nutrient availability for gut bacteria (30) Enrich Bacteroides and Bifidobacterium spp. (30) Prevent pathogen colonization (31) Modify host-microbe interaction (32)	No published evidence, but associations found for atopic sensitization and food allergy (26, 33)
Milk microbiota	Birth mode (22) Mode of breastfeeding (22) Maternal BMI (34) Infant sex (34)	Provide pioneering species (11) Enrich “beneficial” bacteria (35) Increase colonization efficiency	No published evidence