There are many wives tales floating around about babies being overly sensitive to things that a breastfeeding mother passes on to them. While it is true that some babies can be sensitive to proteins in breastmilk obtained from dairy products, most babies are not. A baby cannot become gassy from something the mother ate. Even if a baby is sensitive to something the mother has eaten, it is often much better for the baby to continue to drink breastmilk while having the mother cut back on dairy or any other allergen that may affect the child.

Key Takeaways:

• The main food known to appear in breast milk and cause problems for babies is the cow’s milk protein in dairy products, and then it’s only in babies who are allergic to dairy already. It is estimated that between 2-7 % of babies have a sensitivity to dairy products.
• There are no special dietary rules to follow during lactation. If your eating habits are fairly healthy, there is no reason to change them while you are nursing.
• I suspect that most mothers who swear that they can’t eat (pizza, Mexican food, broccoli, cabbage, beans, chocolate, etc.) while they are nursing are actually overreacting to their baby’s normal behavior on any given day.

“The main food known to appear in breast milk and cause problems for babies is the cow’s milk protein in dairy products.”

https://www.breastfeedingbasics.com/qa/are-babies-sensitive-to-what-mom-is-eating