There are no foods you "have to" avoid while breastfeeding. Some of it is old wives tale (broccoli causes gas in Mom because of the fiber in the food, ..however fiber cannot pass into breastmilk and into baby). Sometimes I would eat something and swear it upset my baby, then other times be fine. One time I thought for sure it was the spicy orange chicken I ate, but then he sprouted 2 new teeth so it was probably teething. Also, newborns and young babies OFTEN have fits of crying/screaming/etc some times for no apparent reason. I didn't cut back on anything while nursing because I could never pinpoint anything specific. As far as how long it takes to get into the milk - Check out this article (too long to copy & paste) http://www.breastfeedingbasics.com/qa/what-i-eat-to-get-into-my-breastmilkView Thread
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