Everything you eat is transmitted through breast milk, but some babies are more sensitive to mom's meals than others. Some breastfeeding moms note that their babies get fussy after they eat cruciferous veggies like brussels sprouts or broccoli, or other foods like onions, chocolate, or dairy. But since many babies get gassy from swallowing air during the course of feedings and crying, it's hard to know how much of a role diet plays, and there's not a ton of research that proves these food sensitivities exist. But if your baby has bloody poops, rashes, or severe pain, a cow's milk protein allergy could be to blame. This is more serious, and should be checked out by your pediatrician.
If you have a very gassy baby, it's probably worth going off any food that seems to be a culprit for a week. If that appears to help, avoid that food until your baby is 2 months old (when gas and crying both tend to peak) or has begun to cry less in general, then try the food again. If the symptoms return, you'll have your own data and then you can decide how much your baby's "fuss food" is worth to you right now. Being gassy isn’t comfortable, but it’s not harmful to your baby. Most of these food sensitivities subside within a few months as your baby's immune and digestive systems strengthen.
Originally published in Child magazine, 2006. Updated 2009.