Rescuing the Microbiome Effectively With Different Doses of B. Infantis in Infants

Inclusion Criteria: * Age of subjects: Infants: 60 to 125 days old, Mothers: 21 years old and greater * Mother-infant dyads who live within a 40-mile radius from the clinical site * Infants predominately breastfed with maternal intent to continue exclusive breastfeeding for at least 9 additional weeks * Term infants born \>37 weeks gestation * Healthy infants without medical complications * Generally healthy women * Mothers who are willing to refrain from feeding their infants infant formula, solid foods, and probiotic or iron supplements (confounding variables of the intestinal microbiome) before the end of the study Exclusion Criteria: * Mothers diagnosed with any metabolic, endocrine, liver, or kidney disease, any autoimmune disease, cirrhosis, hepatitis C, HIV, AIDs, cancer, obesity (pre-pregnancy BMI \>34.9 kg/m2), Crohn's disease, heart disease, type 1 or type 2 diabetes (type 1 diabetes is acceptable if mother's blood glucose has been well-regulated) * Infants born in a multiple birth * Infants born with medical complications such as: respiratory distress syndrome or birth defects * Infants with any GI tract abnormalities * Infants who have taken antibiotics within 4 weeks of enrollment or during the Lead-in Period * Infants who have taken iron supplements within 4 weeks of enrollment or during the Lead-in Period * Infants who have consumed any infant formula within 4 weeks of enrollment or more than 10 times between birth and enrollment or during the Lead-in Period * Infants whose parents plan to feed them any infant formula any time throughout the duration of the study * Infants who have consumed any probiotics containing B. infantis since birth * Infants who have consumed any Bifidobacterium-containing probiotics within 4 weeks of enrollment or during the Lead-in Period * Infants whose parents plan to administer probiotics to them any time throughout the duration of the study (not including the study supplement) * Infants who have consumed any solid foods or beverages between birth and enrollment or during the Lead-in Period (liquid medicines, supplements, and sugar water are ok) * Infants whose parents plan to feed them solid foods or beverages any time throughout the duration of the study * Infants whose mothers have changed their minds about their plans to exclusively breastfeed for at least 8 additional weeks by Day 7 * For infants born vaginally, maternal intake of probiotics containing B. infantis during the last trimester of pregnancy * Mother-infant dyads who live in more than one location * Infants who have been diagnosed with any medical or nutritional condition that would require iron supplementation * Mothers who smoked cigarettes during pregnancy, currently smoke, or plan to initiate smoking during the study duration * Anyone the investigator feels isn't an applicable subject