Alicia Silverstone's video of herself chewing her baby's food last week prompted disgusted comments, but she may actually be doing little Bear Blu a favor. Our ancestors did the same, and plenty of non-Western cultures still do it, Life's Little Mysteries notes. Like breast-feeding, "pre-mastication" offers benefits to a baby. The tiny quantities of germs in a mother's saliva prompt a baby's immune system to produce helpful antibodies.
Getting too little exposure to such pathogens may raise the risk of asthma and other autoimmune diseases, scientists say. There's one caveat: Pre-mastication could cause a baby to catch a disease it's exposed to through the mother's saliva, prompting doctors to warn women with HIV not to pre-chew. But the risks involved appear to be lower than once thought; indeed, the risk is higher from breast milk. "We think the story is identical for both breastfeeding and pre-mastication—they save lives by ensuring good nutrition and good development of the immune system," says a researcher. (Read more Alicia Silverstone stories.)