Akari Hiraku, Riko Mishima, Ayaka Hori, Shinto Kurosaki, Hiroki Kaneko, Ryuta Ejima, Eri Mitsuyama, Kana Kadowaki, Akira Sen, Saho Furukawa, Mai Morozumi, Muneya Tsuda, Hirohisa Izumi, Satoshi Arai, Noriyuki Iwabuchi, Miyuki Tanaka, Yukihiro Hishida, Daigo Ito, Toshitaka Odamaki
Under WHO-recommended infant formula preparation conditions, B. infantis M-63 was detected in nearly all infants, together with a gut microbiota profile characteristic of early infancy. These findings provide in vivo evidence that B. infantis M-63 can reach the neonatal gut and suggest potential biological activity under microbiologically safe and practically relevant preparation conditions.
BACKGROUND: The World Health Organization (WHO) recommends reconstituting powdered infant formula with water at ≥70 °C to reduce the risk of bacterial contamination. While this practice is important for microbiological safety, it may also reduce the viability and/or functional activity of heat-sensitive bioactive components, such as probiotics. However, it remains unclear whether probiotics added to infant formula can reach the infant gut under WHO-recommended preparation conditions.
OBJECTIVE: To evaluate whether Bifidobacterium longum subsp. infantis M-63 added to infant formula can be detected in the neonatal gut when the formula is prepared with water at ≥70 °C following WHO recommendations.
METHODS: In this exploratory, randomized study with two supplementation levels, 34 term neonates received formula containing B. infantis M-63 reconstituted according to WHO-recommended conditions, from birth to 1 month of age. Fecal recovery of the administered strain was assessed, together with analyses of gut microbiota composition and fecal metabolite profiles. Concurrent breastfeeding was permitted without restriction to reflect real-world feeding practices.
RESULTS: Although reconstitution at ≥70 °C substantially reduced viable bacterial counts in the prepared formula, B. infantis M-63 was detected in fecal samples at high rates at 1 month of age (low-dose 94.4%, high-dose 100%), with no significant differences in detection rates or fecal counts between dose groups. Gut microbiota composition shifted toward a Bifidobacterium-dominant profile over time regardless of dose. In addition, fecal recovery of the administered strain was positively associated with specific tryptophan-derived metabolites, including indole-3-lactic acid (ρ = 0.509, p = 0.002).
CONCLUSIONS: Under WHO-recommended infant formula preparation conditions, B. infantis M-63 was detected in nearly all infants, together with a gut microbiota profile characteristic of early infancy. These findings provide in vivo evidence that B. infantis M-63 can reach the neonatal gut and suggest potential biological activity under microbiologically safe and practically relevant preparation conditions.