I haven't read all the posts on what causes gas in a baby, so forgive me if
this has been stated already.  In my prenatal bfing classes, I discuss how
baby gets gas in relation to breastfeeding and bottlefeeding.  (I show that
"angled bottle" which is advertised as preventing baby from taking in air
while feeding.) I remind moms that baby gets air by breathing while at the
breast and if she has a strong letdown or baby is gulping, that could be part
of it.  Try it yourself, chug-al-lug a glass of water or any beverage, you
will take in air and burP.  (My teenagers demonstrate this for us frequently
- and I have girls!) Also, remember that food (whatever is in your
stomach/intestines, etc.) ferments as it digests and that everyone has gas
sometimes.
Just my observations and comments,
MK Smith, IBCLC, CLE
Romeoville, IL