What shouldn’t you eat while breastfeeding?

“Banned lists” have done the rounds among mums for generations. They can get so confusing that some mothers simply give up on the rules altogether. The truth? Some old tips are based on misunderstandings, but there are foods and ingredients it’s wise to avoid while breastfeeding.

We tend to focus on pregnancy, doing everything we can to create the healthiest lifestyle until baby arrives. But breastfeeding keeps you connected through your milk – so what you consume can affect them, too.

When baby has tummy pain or cries, it’s easy to blame your last meal. Remember: only about 1% of babies are sensitive to a specific food component, so it’s unlikely to be that day’s breakfast. There are plenty of other reasons for tummy aches and crying – we’ve covered these in a previous article; have a read if it’s relevant to you: your baby’s tummy aches

What “don’t-eat” rules do mums talk about most?

Among mums you’ll hear all sorts – passed on via tradition, personal stories, or half-truths. Some are sensible, others not evidence-based. First, here’s the typical banned list you’ll hear about – then we’ll look at it from a professional angle.

Common (often non-clinical) “avoid” list:

• Gas-forming foods said to cause baby tummy pain – the famous “K-veg” and brassicas (kale, broccoli, cauliflower), legumes (beans, lentils, peas), onions

• Citrus / acidic foods – thought to “sting” baby’s bottom or make milk “acidic” (orange, lemon, grapefruit, tomato)

• Caffeine – feared to cause sleep issues or overstimulation

• Spicy foods – may alter milk taste (hot peppers, garlic, curry, chilli)

• Sea fish / seafood – mercury concerns and allergy risk

• Common allergens – dairy, eggs, nuts, soya, gluten

• Alcohol

What do professionals actually suggest avoiding?

Opinions vary. Current understanding: aside from a few sensible limits, you generally don’t need to cut out lots of foods. Something that affects you won’t necessarily affect baby. For example, the wind you get from legumes forms in your bowel – it doesn’t pass into milk – so it won’t make baby gassy.

It can be reasonable to reduce higher-allergen proteins (egg, dairy, fish) if you suspect a sensitivity – but with a healthy baby you don’t need to eliminate them to “prevent” allergy.

Do keep an eye on additives in shop-bought foods, chemical residues, and medicines. Some large sea fish can be high in mercury, so they’re not recommended while breastfeeding. Alcohol isn’t recommended either, as it can pass into milk and may inhibit let-down.

Caffeine (coffee, black tea, caffeinated soft/energy drinks) does pass into milk and can cause restlessness or sleep disruption in some babies.

Certain foods – raspberries, strawberries – can flavour your milk, and some babies aren’t keen. Similarly, strongly aromatic spices (pepper, hot chillies, sage, horseradish, chilli) may be noticeable.

Not a food, but important: nicotine from smoking can appear in breast milk at higher concentrations than in mum’s blood – another reason to avoid it.

If you suspect a particular food, try removing it for 2 months, then re-introduce. That’s usually enough time for symptoms to settle. And whenever you’re unsure about foods or medicines in breastfeeding, ask your GP/health visitor.

What is worth taking?

Continuing a pregnancy multivitamin post-partum can be helpful. Probiotic supplements taken by mum may support digestion, help baby’s gut maturity, and may reduce allergy risk. Omega-3 fatty acids offer strong support for baby’s nervous system.

Omega-3 and mercury in fish 

Omega-3s are beneficial for nervous system development, but mercury can accumulate in some fish due to water contamination. Methylmercury is neurotoxic for developing babies; even low amounts in early life can hinder neural development and later relate to attention or cognitive issues. Mercury mainly enters via large sea fish and marine mammals.
Choose low-mercury fish 1–2 times a week, in line with professional advice.

Why can an overly restricted diet be a problem? 

If mum avoids too many foods or eats very one-sidedly, nutrients needed for milk composition are drawn from her own stores – which may be insufficient. Also, when fat stores are broken down, not only useful nutrients but fat-soluble toxins can enter breast milk – for example heavy metals. The same applies if a breastfeeding mother goes on a strict diet.

Mum’s diet and lifestyle affect milk quality and quantity 

Breast milk is the ideal infant food. To meet the extra energy and nutrient needs of breastfeeding, mum needs roughly an extra 600–700 kcal/day across 4–5 meals. Protein needs also rise by about 20 g/day.

Vitamins and minerals matter more too – especially A, D, C, folate, calcium, magnesium, phosphorus, iodine, zinc. And yes, fluids are important to support milk production.

Sources:

NHS – Food and drinks to avoid when breastfeeding

NHS – Drinking alcohol when breastfeeding: practical guidance.