Baby food intolerance

I'm trying to figure out if there is something in my diet that may be causing a food intolerance in my LO, but have a quick question! How long does the food I eat take to reach my breastmilk? E.g. If I drink a glass of cow milk now, which feeding would have the cow milk that passes to my LO (of course depends on WHEN the "next feeding" is, so a timeframe may be more helpful)?