The research team led by Dr. Jeffrey Gordon had discovered that sialylated milk oligosaccharides found in human breast milk are the key components in aiding growth in gut microbia in healthy babies.  Selecting Malawian mothers with 6-month old healthy and stunted babies, they have discovered that mothers with stunted growth infants lack the sugars found in mothers with healthy infants.  To verify their findings, the group compared the effect on germ-free mice, one group was introduced to cultured fecal microbia from infants with stunted growth while the other group remained as is.  Both groups were fed Malawian diet with the presence of the sugars.  Results show that gnotobiotic mice have improved liver, muscle and brain development compared to germ-free mice.  Results are also the same with gnotobiotic piglets.  Read more about their work here.