““It earns its keep. As it digests HMOs, B. infantis releases short-chain fatty acids (SCFAs) that feed an infant's gut cells - so while mothers nourish this microbe, the microbe in turn nourishes the baby. Through direct contact, B. Infantis also encourages gut cells to make adhesive proteins that seal the gaps between them, and anti-inflammatory molecules that calibrate the immune system. These changes only happen when B. infantis grows on HMOs; if it gets lactose instead, it survives but doesn't engage in any repartee with the baby's cells. It unlocks its full beneficial potential only when it feeds on breast milk. Likewise, for a child to reap the full benefits that milk can provide, B. infantis must be present. For that reason, David Mills, a microbiologist who works with German, actually sees B. infantis as part of milk, albeit a part that is not made in the breast.””
