Shelf-stable donor breast milk provider Leche and at-home microbiome testing firm Tiny Health have announced a joint clinical study to evaluate the impact of donor breast milk on the gut health of formula-fed infants.
The initiative represents one of the first clinical trials applying modern shotgun metagenomics sequencing to shelf-stable donor milk. The trial will specifically measure whether supplementing a formula-fed infant's daily diet with a small quantity of donor breast milk induces measurable, beneficial shifts in gut microbiome composition and functional capacity.
The clinical research aims to establish scientific data for combination feeding strategies, addressing a segment where an estimated two-thirds of American infants receive formula during their first year.
While the role of human milk in establishing infant gut flora is well documented, formula formulations typically replicate only one or two human milk oligosaccharides (HMOs). In contrast, donor breast milk contains a natural spectrum of roughly 150 to 200 distinct HMO sugars that survive pasteurisation intact, serving as targeted prebiotics for beneficial gut bacteria.
Trish Clifford, Co-Founder of Leche, stated that the majority of parents rely on a combination of feeding methods rather than exclusive breastfeeding or formula feeding alone. Clifford noted that the study was designed to generate clinical evidence regarding the health outcomes of adding a daily portion of donor milk to a formula-based diet.
Trial Methodology and Microbiome Testing Framework
The study utilises a before-and-after trial design involving 100 healthy, full-term, formula-fed infants. Baseline gut microbiome profiles will be established upon enrolment using Tiny Health's testing platform. Participating families will then integrate Leche's powdered donor breast milk into daily formula feeds for a 30-day trial period, followed by end-of-study microbiome sequencing.
Cheryl Sew Hoy, Founder and Chief Executive Officer of Tiny Health, highlighted that the trial utilises shotgun metagenomics to assess whether modest daily quantities of donor milk enable beneficial bacteria to colonise the infant gut during a critical developmental window.
Researchers will evaluate several primary endpoints:
🦠 Bifidobacterium Levels: Tracking quantitative increases in beneficial bacterial strains that typically dominate the gut flora of breastfed infants.
🍼 HMO Utilisation: Assessing whether the infant gut microbiome develops the functional gene pathways required to process complex human milk sugars.
📈 Microbiome Composition: Measuring whether overall microbial diversity and community structure shift toward a profile characteristic of breastfed infants.
Research Timeline and Participant Enrolment
Participant sign-ups for the study officially open on 1 August 2026, with enrolment capped at 100 participants or closing on 15 August 2026.
Enrolled families are scheduled to begin the feeding protocol in September 2026, with preliminary results expected to be published later in the year.
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