Breastfeeding Diet: What to Eat, What to Avoid, and What's a Myth

The list of things people tell breastfeeding mothers to avoid is remarkably long — and mostly unsupported by evidence. Here's what actually matters.

The reassuring truth: most foods are fine

Breast milk is produced from your blood, which draws nutrients from your body's stores as well as your recent diet. Your body is remarkably good at maintaining breast milk composition even when your diet is imperfect. The idea that you need a strictly controlled diet is largely a myth.

Across the world, women breastfeed while eating spicy food, raw fish, strong cheese, garlic, cruciferous vegetables, beans, and every other food that gets placed on "avoid" lists — and their babies are fine.

What genuinely does pass into breast milk

Alcohol: Yes, alcohol passes into breast milk. Levels peak at about 30–60 minutes after drinking. The current NHS guidance: avoid alcohol in the first 3 months. After that, if you do drink, a single drink of standard strength is generally considered low risk — wait at least 2 hours before breastfeeding. The alcohol clears from milk as it clears from your blood.

Caffeine: A small amount passes into breast milk. Most babies are not affected. Guidance: limit to 300mg/day (about 2 cups of strong coffee, or 4 cups of tea). Some sensitive newborns may be affected by caffeine — if your baby seems unsettled after you've had coffee, try cutting back.

Mercury in fish: Certain high-mercury fish (shark, swordfish, marlin, king mackerel) should be limited — no more than twice a week for these species. This is consistent advice across pregnancy and breastfeeding. Other fish (oily fish, white fish, shellfish) are safe and healthy.

Some medications: Most common medications are compatible with breastfeeding. The LactMed database (accessible online) and the Breastfeeding Network's Drug Factsheets (breastfeedingnetwork.org.uk) are authoritative resources. Always check before taking any new medication.

Flavours: Yes, flavour compounds from food you eat do appear in breast milk — garlic, curry, vanilla, etc. This is generally a benefit, not a problem. Exposing babies to varied flavours through breast milk may make them more accepting of those foods when weaning.

Does my diet affect supply?

Caloric intake: Yes, meaningfully. Breastfeeding requires approximately 400–500 extra calories per day. Severe caloric restriction can reduce supply. Eating enough is the most important dietary variable.

Hydration: You need approximately 500–700ml more fluid per day than before breastfeeding. Mild dehydration can reduce supply. Drink water or other fluids frequently — a glass of water at every feed is a useful habit.

Specific "galactagogues" (supply-boosting foods): Oats, fenugreek, fennel, and various herbs are claimed to boost supply. The evidence is weak. If you eat these foods and enjoy them, there's no harm. Eating them in the hope of fixing a supply problem is unlikely to work. Address supply concerns with a lactation consultant.

Supplements recommended during breastfeeding

Vitamin D: The NHS recommends all breastfeeding mothers take 10 micrograms (400 IU) of vitamin D daily. The UK doesn't get enough sun for most people to maintain adequate levels, and breast milk is low in vitamin D unless the mother has good levels.

Omega-3 (DHA): DHA is important for infant brain development. Include oily fish in your diet (1–2 portions per week — salmon, mackerel, sardines, trout) or take an algae-based omega-3 supplement.

Iron: If you had low iron in pregnancy or a blood loss at birth, your stores may be depleted. Red meat, legumes, leafy greens, and iron-fortified foods help. If very fatigued, ask your GP to check your iron levels.

Iodine: Iodine is important for thyroid function and baby's brain development. UK diets can be low. Sources: dairy, fish, eggs. Consider a pregnancy/breastfeeding multivitamin that includes iodine (note: kelp supplements have inconsistent iodine levels and are not recommended).

The foods people tell you to avoid (and what the evidence actually says)

Gassy foods (broccoli, cabbage, beans, onions): Gas from food does NOT transfer to breast milk. The compounds that cause gas in your gut are not absorbed into the bloodstream and cannot appear in milk. Your broccoli is not giving your baby wind.

Spicy food: No evidence that spicy food causes problems for most breastfed babies. Many cultures eat spicy food throughout breastfeeding without issue.

Dairy: Unless your baby has been diagnosed with cow's milk protein allergy (CMPA), there is no need to restrict dairy. A small proportion of breastfed babies do react to dairy proteins passed through milk — if your baby has significant symptoms (blood in stool, severe eczema, obvious distress after feeding), speak to your GP or health visitor about a dairy elimination trial.

Caffeine: Fine in moderate amounts (see above). No need to cut it out entirely.

Alcohol: Limit and time carefully (see above). Not prohibited entirely after 3 months.

Realistic nutrition goals

Rather than restrictions, focus on:

• Eating enough calories — don't restrict intake while breastfeeding
• Protein at every meal — meat, fish, eggs, dairy, legumes
• Iron-rich foods — especially in the first months after birth
• Oily fish 1–2 times a week
• Plenty of water
• Vitamin D supplement

A varied, balanced diet that you enjoy is far better for you and your baby than a restricted diet that causes stress and deprivation. The evidence supports the former.