Breastfeeding and Maternal Diet

Lactation is a normal physiological process for postpartum women. All mothers should eat well, although not perfectly, every day to ensure health and wellbeing regardless of breastfeeding status. 

A healthy diet should consist of a wide range of foods. A simple  breakdown of a lactating woman’s diet  should be 50-55% carbohydrates ( complex), 12-15% protein and 20-30% fats ( unsaturated, non-trans fatty acid). 

Maternal food and fluid intake does not impact milk volume unless the mother is significantly malnourished or dehydrated. 

Allergies and avoiding food 

There is little evidence to support avoiding certain foods during breastfeeding such as garlic, onion, leafy greens to avoid issues such as wind pain. 

Foods that seem to be causing an issue for a baby can be avoided in the maternal diet for at least  2 weeks ( but up to 6 for dairy) to see if there is any improvement in signs/ symptoms or if a flare up occurs when reintroduced.  Removal of lots of foods or food groups should be done under the supervision of a dietician and medical professional . A food and symptom diary may be able to help pinpoint problematic foods  . 

A diagnosed cows milk protein allergy ( CMPA) in a baby will mean the breastfeeding mother will need to remove all cows milk products from her diet as this protein does cross over into the breastmilk.Some mothers also find their child also reacts to goat milk products. 

 Breastfeeding mothers should drink to thirst. Pale , odourless urine is a good indicator of hydration. There is little evidence that increasing water intake will consequently increase breastmilk supply and in fact excessive fluid intake has actually shown to reduce milk production. 

Hormones released when breastfeeding can induce a thirst sensation. Having a bottle of water nearby that is easy to use with one hand, when feeding helps ensure mothers stay hydrated during their busy days. 

Weight- Over or Under 

Being underweight ( BMI <18.5) or overweight ( >25 BMI ) can have different effects on breast milk and breast milk composition.  Underweight mothers may have poor diets due to a number of reasons  e.g. mental health, finance, malabsorption  and therefore suffer from  insufficient consumption of micronutrients. The micronutrients in breastmilk that are affected by low maternal status are:  Thiamin, Riboflavin, Vit B6, Vit B12, Vit D, Vit A and selenium . Nutrients in breastmilk not generally affected by maternal status are zinc, iron, folate and calcium. 

Overweight mothers also may suffer issues that can effect breastfeeding such as: 

  • More likely to have delayed lactogenesis 11 ( Milk coming in) 
  • Increased risk of c section which can set off cascade of interventions that interfere with breastfeeding ( no or delayed skin to skin,  delayed first feed, special care nursery admission, sleepy baby and mother due to medications). 
  • More likely to have oversized breasts and may need additional help with positioning or feel like they are smothering baby with breasts. Nipples may be short or flat due to size of breast. 
  • More likely to have larger baby ( 4.5kg) and be pressured to supplement 

Other groups of people may have food/ nutrient related issues that may affect breastfeeding such as . 

  • Teenage mothers may have diets low in iron and calcium due to their eating habits and rapid growth.  
  •  Mothers who have had weight loss surgery such as gastric bypass are at higher risk of nutritional deficiencies due to malabsorption. 
  • Those with allergies or self imposed dietary restrictions may suffer from micronutrient deficiencies such as B12.  

Exercise and maternal weight loss. 

Being physically active has many benefits for mothers such as increased health and wellbeing status, weight loss, increase in bone and muscle strength, reduction in stress and improved mental health. 

Research has found that mild to moderate exercise does not cause an increase in lactic acid in breastmilk. Any increase may change the taste slightly, but will cause no harm to the baby. Exercise has shown to have no impact on milk supply. Milk production and breastfeeding burns about 500 calories a day but maternal weight loss or return to prepartum weight is dependent on activity level, food choices, individual metabolism and daily calories consumed. 

Mothers who exercise strenuously for more than 1 hour a day, may need to consume additional calories if they feel they are losing a lot of weight. 

The effects of relaxin, a hormone present in pregnancy to help make the ligaments more elastic in preparation for childbirth) can stick around for up to 6 months post birth. Mothers should be careful when exercising not to injure themselves and listen to their bodies. 

Breastfeeding prior to exercise can make it a more comfortable experience. Full breasts can be heavy and painful when exercising.  Wearing a supportive and comfortable bra is essential. Specific breastfeeding sports bras can help make combining exercising when breastfeeding easier.  Mothers should try to replace lost fluids from vigorous exercise and sweating to ensure they don’t feel the effects of dehydration. 

Exercising with the baby ( e.g. mums and bubs fitness classes or low impact activities such as walking with pram or with baby in carrier) can help with combining breastfeeding and exercise. It reduces the need to have them looked after while you exercise, which may cause anxiety or distress to the mother, baby or person looking after them or  missing feeds which can lead to  engorgement or  reduction in supply. 


Most infants are not bothered by the maternal intake of coffee or caffeinated foods/beverages, but has been shown to cause fussiness, alertness and sleep disturbances in some infants. Caffeine in breast milk is 0.96-1.5% of the maternal dose so usually up to 300 mg/day of caffeine is tolerated well. Preterm or ill infants may not metabolise caffeine well and it may accumulate in their symptoms leading to negative side effects. 


Alcohol passes freely into breastmilk and back into the maternal bloodstream when being metabolized by the liver.  There is not a documented “safe” level of alcohol when breastfeeding and it is up to each individual to decide when and if to feed after consuming alcohol.

Alcohol levels peak in breast milk approximately 30-60 minutes after consumption on an empty stomach vs 60-90 when consumed with food.  

Breast milk does NOT need to be “pumped and dumped”. Only time will reduce blood alcohol level/ levels of alcohol in the breast milk. 

Large amounts of alcohol in breastmilk can cause drowsiness in infants and over long periods it can cause slow growth and neurodevelopmental delays. High intakes of alcoholic beverages can impair the milk ejection reflex and impair the mothers ability to care for their infant. 

There are apps to help calculate when it may be “safe” to feed again after drinking. If a mother is wanting to avoid breastfeeding while drinking, she could give pre-pumped EBM, donor milk or formula. 

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