Truthsweet La Leche League suggest the following:
"Breastfeeding mothers may wonder if diet plays a role in causing gas in breastfed infants. The Le Leche League International suggests that while no food has been specifically proven to cause gas in breastfed infants, mothers should consume a healthy, balanced diet and keep track of foods suspected of upsetting baby's tummy for future reference. Some common foods, however, are widely thought to cause or exacerbate infant gas in breastfed babies.
Vegetables and Legumes
Vegetables high in fiber are often believed to cause gas and fussiness in breastfed infants. Broccoli, peppers, cabbage and Brussels sprouts can cause gas and internal discomfort. Similar components in these vegetables known for causing gas may be passed onto infants during breastfeeding. Additionally, legumes such as kidney beans, lima beans and black beans produce gas and can be triggers for gassy tummies.
Caffeine
The effects of caffeine are not necessarily associated with gas; however, it is related to causing irritability in breastfed babies. Infants already suffering from gas or internal discomfort may feel additionally uncomfortable from consuming caffeine in breast milk. Many foods and drinks contain caffeine, such as coffee, tea, soft drinks and chocolate. While appropriate in moderation, caffeine-laden drinks should be limited to two 8-oz. servings per day during breastfeeding to reduce the chance of infant irritability and discomfort.
Dairy
Dairy products may cause gas and discomfort in any baby, however this may be more prevalent in babies whose mothers are lactose intolerant or have a known dairy allergy. Dairy proteins from foods such as milk, cheese, ice cream and cottage cheese, are passed into breast milk and transferred to baby during nursing. Infants sensitive to dairy protein can develop indigestion, intestinal gas and discomfort, which may be reduced or eliminated by removing dairy from the breastfeeding diet.
Spices
Garlic, cumin, curry and red pepper are commonly thought to be culprits for causing intestinal gas and upset in breastfed infants. Spices in general are widely used in different cultures of breastfeeding mothers. The Children's Hospital of Boston notes there is no one specific spice or food known to cause gas in all babies, though some may be more sensitive to spices than others.
Acidic Foods
Foods high in acid content can cause infant digestive discomfort, as well. Citrus-based foods such as tomatoes, strawberries, oranges and grapefruit are highly acidic, and can be monitored in moderation to see if breastfeeding after consuming these foods has any effect on baby."
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