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Many U.S. babies may lack gut bacteria that train their immune systems

Missing the microbes is linked to a higher risk of allergies and other health issues

Close up of a one-week-old baby boy with dark hair and eyes. He is wrapped in a white towel and clutching the thumb of an adult wearing a gold ring. His lips are pursed as if cooing.

Many babies born in the United States lack important gut microbes that digest breast milk and help train the immune system.

Vicki Smith/Getty Images

By Tina Hesman Saey

About three quarters of babies born in the United States may not have enough friendly microbes in their guts to protect against developing allergies, asthma and eczema, a new study suggests.