Can What You Eat While Breastfeeding Affect Your Baby?

We've all heard the saying "you are what you eat." But if you're breastfeeding, you might be wondering: Does that mean your baby is what you eat, too? It's a fair question. After all, so many foods were off-limits during pregnancy, and it's not always clear whether the same rules apply now, especially when it comes to eating fish and other potentially restricted foods.

Luckily, most of your favourite meals are back on the table. Still, some foods, drinks and even supplements can affect your milk supply or how your baby feels after feeding. And since advice can differ depending on whether you're hearing it from friends, TikTok or your pediatrician, it can feel hard to know what's actually true.

That's why we asked experts how your diet affects your breast milk and your baby’s health—from foods that may upset tiny tummies to whether allergenic foods really matter—so you can feel confident about what’s on your plate.

How your diet impacts breast milk and your baby's health

What you eat doesn't just fuel you; it can influence your milk and, in some cases, your baby's nutrition too. Mindy Cockeram, a board-certified lactation consultant and a Lamaze Certified Childbirth Educator, explains that certain nutrients (and yes, some substances) pass from your bloodstream into breast cells and then into the milk-producing alveoli. The catch? "Not all nutrients, such as iron from leafy greens or dried fruits, are transferred at the same rate," she notes.

This is why eating a nutrient-dense diet, including well-planned vegan diets, is especially important during this stage. Cockeram says that your body is wired to produce the best milk possible, sometimes at your own expense.

"If a mother is deficient in nutrients, her body will pull from stores and she'll get depleted," she explains. "For example, if her diet is low in sources of protein, it will be pulled from her muscles."

Foods and drinks to strictly limit or avoid

Breastfeeding doesn't come with a fully restricted menu, but there are foods worth strictly limiting or avoiding. For example, Maribel Sanchez, IBCLC, an international board-certified lactation consultant, says that alcohol is at the top of the list.

Alcohol

"Alcohol levels in breastmilk are the same as alcohol levels in a lactating mother’s bloodstream," Sanchez explains. "When a mother decides to drink alcohol, it enters her bloodstream and consequently passes into the breast milk. "

That said, it's not as strict as pregnancy rules. A glass here and there can be okay. "Current research says that occasional use of alcohol (1-2 drinks) does not appear to be harmful to the breastfed baby," Sanchez says. "Many experts recommend against drinking more than 1-2 drinks per week."

Caffeine

Your morning coffee doesn't have to be off limits while breastfeeding. As Sanchez explains, most breastfeeding mothers can sip two or three cups of coffee a day without issue.

Even so, every baby is different. "Some babies may have different sensitivities to caffeine," she says. "If you notice any adverse effects in your baby after consuming caffeine, such as unusual fussiness, sleep problems, or a rapid heart rate, consult with your healthcare provider."

High-mercury fish

High-mercury fish—such as shark, swordfish, king mackerel, and tilefish from the Gulf of Mexico—should be avoided entirely by those who are breastfeeding, as mercury can be transferred through breast milk.

Instead, both the U.S. Food & Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC) suggest sticking with lower-mercury options and enjoying a mix of them a couple times a week (about 8 to 12 ounces).

Herbal teas and supplements

Herbal teas and supplements can seem like harmless add-ons, but some may interfere with milk supply.

Sharon Berger, IBCLC, RN, an international board-certified lactation consultant and registered nurse, notes that peppermint, parsley, and sage may reduce milk production in certain people.

"If your milk supply is strong, it might not make a big difference," she explains. "But for anyone who is struggling, it's something to be mindful of."

Foods that may cause discomfort or reactions

Shira Sussi, MS, RD, CDN, a registered dietitian nutritionist, says some foods cause your baby discomfort while nursing. Dairy, she adds, tends to be one of the main culprits.

Dairy products

“Cow’s milk protein allergy (CMPA) often shows up early—usually before six months—since babies can be exposed through breastmilk or formula,” explains Sussi. There are two types: IgE-mediated, where symptoms pop up within about two hours, and non-IgE-mediated, which tends to unfold more slowly, over the course of hours or even days.

If your little one isn’t tolerating dairy, some of the red flags include skin reactions like rashes or hives, digestive issues, and, in more severe cases, breathing difficulties or anaphylaxis.

Gassy foods

Cruciferous favourites like broccoli and cauliflower get blamed for making breastfed babies gassy, but according to Sussi, the science isn't exactly settled.

"Some believe that certain foods like cruciferous vegetables cause breastfed infants to be more colicky, but research shows conflicting results," she notes. "If your breastfed baby is continually irritable, however, I recommend ruling out food intolerances or reflux first with the guidance of a pediatrician before cutting out nutrient-dense foods from your diet."

Spicy foods

Spicy foods do influence breastmilk, but not the way you'd imagine.

"Spicy foods can affect the taste and aroma of breastmilk, but in very small amounts — not enough to make your milk 'spicy', but enough to expose your baby to a variety of different flavour profiles that can make them more likely to accept these flavours when introduced to solid foods," Sussi shares.

Allergenic foods

Allergenic foods like peanuts, tree nuts, soy, wheat, and eggs naturally raise questions for many breastfeeding women. That's because, as Sussi explains, the research on whether a mother's diet can influence her allergy risk is still growing.

"We know from major studies like LEAP and EAT that introducing allergens early during solid food introduction can decrease allergy risk," she says. "But when it comes to whether a breastfeeding parent should avoid or load up on those foods, the evidence just isn’t there yet."

The encouraging news? Once your little one hits the four-to-six-month solid food window, Sussi suggests that the best thing you can do is steadily introduce these common allergens and keep offering them consistently.

Common myths and misconceptions about breastfeeding diets

Food and breastfeeding spark endless questions—and just as many myths. To clear things up, Berger breaks down the biggest misconceptions you're most likely to see online or hear in everyday conversations.

Myth 1: Cutting allergens out keeps your baby safe

Turns out, the science says otherwise. "When the maternal diet includes allergens, the baby's immune system is exposed to that protein, and it seems less likely to develop an allergic response later when they ingest that food themselves," explains Berger. "In other words, eating peanuts while pregnant might actually help your baby down the road."

Myth 2: Breastfeeding mothers need to eat plain foods

Berger points out that research actually shows the opposite. "In fact, there is research showing that breastfeeding exposes babies to more varieties of flavours, since breast milk flavour is influenced by the maternal diet," she shares.

Myth 3: You need to drink milk to produce milk

"This one is also not true at all," says Berger. "While calcium is key for breastfeeding, yogurt, leafy greens, canned salmon, and even sardines are all excellent calcium sources that give your body what it needs."

What to eat for a healthy breastfeeding diet

For the best nourishment—for you and your little one—Caitlin Wilder, a certified lactation consultant, childbirth educator, and full-spectrum doula, emphasizes the importance of following a healthy breastfeeding diet.

"Moms need all of that good fuel and energy to put up with the demands of breastfeeding, she explains. "You can burn between 300-700 additional calories a day breastfeeding, so you want to make sure you're eating a balanced diet to keep your energy up."

Focus on key nutrients

Nutrition plays a major role in supporting both recovery and milk supply postpartum. Key nutrients to pay attention to include iron, protein, and calcium.

"Many women, especially after childbirth, are deficient in iron," Berger explains. "Iron-deficiency anemia can cause low energy levels and low milk production."

She continues, "Protein is important for many functions in our body, so I would also focus on that. Calcium is another one that many of us are low in, and our bones get depleted if our diet is deficient. Other important nutrients are zinc, magnesium, folate, vitamin B6, and thiamine."

Embrace a variety of foods

Berger says that all of these foods deserve a spot on your plate since they pack in both variety and nutrients.

In fact, a 2024 Cleveland Clinic article points out that whole grains deliver a boost of fibre, vitamins, and carbohydrates, while healthy fats —like omega-3s found in salmon and sardines—help support your baby's brain and nervous system development.

Information from the Office of Disease Prevention and Health Promotion (OASH) adds that fruits and vegetables such as apples, sweet potatoes, berries, and spinach are also smart choices, since they provide vitamins and minerals like vitamin A, potassium, and vitamin C, all of which aid healthy infant growth.

And per the Mayo Clinic, lean meats—such as poultry, dairy, eggs, lentils, beans, and low-mercury seafood—round out a balanced breastfeeding diet.

Stay hydrated

“Adequate hydration is important, both for milk making and for the mother to feel good,” suggests Berger. “However, as much as we don’t want mothers to be under-hydrated, we also don’t want them to be over-hydrated.”

That said, Berger states that a good rule is to drink a glass of water whenever you nurse or pump. She adds, “Keep an eye on the lightness of your pee — concentrated urine is a sign that you need more hydration, and clear urine may be a sign that you’re overdoing it.”

When to call your doctor

For the most part, breastfeeding and figuring out food choices aren't complicated. But sometimes, it's worth looping in your pediatrician.

Katie Clark, IBCLC, an international board-certified lactation consultant and the owner of The Breastfeeding Mama, says that there are a few red flags parents shouldn't ignore: blood in your baby's diapers, consistently mucousy and green stools, and extreme reflux/colicky behaviour.

When questions come up about medications or supplements, Clark recommends consulting a professional about specific medications or supplement concerns that you may have. "Most medications and supplements are compatible with breastfeeding, but if you have any concerns, reach out to an IBCLC or an organization like Infant Risk," she advises. "It's better to be careful."

And if you suspect that your baby might be reacting to something in your diet, that's another area where professional guidance really matters. Clark points out that handling elimination diets on your own can be overwhelming. “There are a lot of changing guidelines and recommendations on elimination diets these days, and it's important to make sure you are working with someone who is up to date on the current research."

Experts

1. Mindy Cockeram, IBCLC, LCCE, is a board-certified lactation consultant and a Lamaze Certified Childbirth Educator.
2. Maribel Sanchez, IBCLC, is an international board-certified lactation consultant.
3. Sharon Berger, IBCLC, RN, is an international board-certified lactation consultant and registered nurse.
4. Shira Sussi, MS, RD, CDN, is a registered dietitian nutritionist.
5. Caitlin Wilder is a certified lactation consultant, childbirth educator, and full-spectrum doula.