Probiotics When Breastfeeding: What the Research Actually Shows

Probiotics are live microorganisms that, when consumed in adequate amounts, may confer a health benefit on the host. They are found in fermented foods (yoghurt, kefir, sauerkraut, miso, tempeh) and in supplement form as capsules, powders, or drops.

Breastfeeding places significant demands on the body. Hormonal shifts, physical recovery from birth, disrupted sleep, and the nutritional demands of milk production all affect the gut environment. It’s common for postpartum mothers to experience digestive changes, reduced gut flora diversity, and increased susceptibility to infections including thrush and mastitis. This is part of why probiotics have attracted research attention in the perinatal period.

The key strains most studied in breastfeeding and postpartum populations fall into two main families:

• Lactobacillus strains — particularly L. rhamnosus GG (LGG), L. reuteri DSM 17938, and L. acidophilus
• Bifidobacterium strains — particularly B. longum BB536, B. infantis EVC001, and B. lactis

These are the strains with the most robust research in maternal and infant health contexts. When evaluating any probiotic supplement, strain specificity matters considerably more than general “live cultures” claims.

This is the first question most mothers ask, and the evidence is reassuring. Multiple meta-analyses and randomised controlled trials have found that probiotics are generally regarded as safe (GRAS) for healthy breastfeeding mothers and their babies. Systemic absorption is rare in healthy individuals, meaning probiotic bacteria are unlikely to cross into the bloodstream and are not expected to transfer meaningfully into breast milk in ways that pose risk.

A comprehensive review published in the Canadian Family Physician found no evidence of increased adverse outcomes in pregnant or lactating women taking probiotic supplements, and no published studies have shown harm to breastfed infants from maternal probiotic use.

That said, standard caveats apply:

• If you or your baby have immune-compromising conditions, check with your healthcare provider before starting any supplement
• Probiotic supplements in Australia are classified as complementary medicines and are not subject to the same pre-market clinical evidence requirements as pharmaceuticals
• Individual responses vary — some mothers notice changes to digestion (loose stools, bloating) when starting probiotics, particularly at higher doses
• Not every strain has been studied in every situation — safety data is strongest for the Lactobacillus and Bifidobacterium strains listed above

For the vast majority of healthy breastfeeding mothers with no underlying conditions, taking a quality probiotic supplement appears to be a safe addition to the postpartum nutrition routine.

One of the more remarkable findings in recent breastfeeding research is that breast milk is not sterile. It contains its own microbiome — a diverse community of bacteria that plays a role in seeding and shaping the infant gut. And the composition of that breast milk microbiome appears to be significantly influenced by the mother’s own gut flora.

This connection operates through what researchers call the entero-mammary pathway — a mechanism by which beneficial bacteria from the maternal gut can travel via the lymphatic and circulatory system to the mammary glands, and from there into breast milk. This means that what you consume (including probiotic supplements) may influence not just your own gut health but the microbial content of the milk your baby receives.

A 2023 systematic review and meta-analysis published in the American Journal of Obstetrics & Gynecology Maternal-Fetal Medicine analysed 24 randomised controlled trials including 2,761 mothers and 1,756 infants. It found that maternal probiotic supplementation was associated with a 24% increase in the detection rate of beneficial bacteria in breast milk, alongside increased beneficial bacteria and decreased pathogenic bacteria in the infant gut. This is a meaningful finding: it suggests that maternal probiotics may positively influence the microbial environment that breastfed infants receive from birth.

A 2024 observational study published in Frontiers in Nutrition found that mothers who took probiotics during lactation had lower levels of inflammatory markers (CRP and IL-6) in their breast milk, and their infants showed higher abundances of Bifidobacteria and Lactobacillus in stool samples at one and six months of age. These are the strains most associated with healthy infant immune development.

It’s important to note that this research is still emerging. The studies are promising but heterogeneous — they vary in probiotic strains used, doses, duration, and populations studied. ‘Associated with’ does not mean ‘causes,’ and the individual variability in response is real. But the direction of the evidence is positive.

Strain specificity is arguably the most important factor when choosing a probiotic supplement. The general statement “this product contains live cultures” tells you very little about whether those cultures are the right ones for your situation or have been studied in populations like yours.

Here are the strains with the strongest evidence base for breastfeeding and early postpartum health:

• Lactobacillus rhamnosus GG (LGG): Widely studied for gut health, immune support, and reducing infant colic. One of the most researched probiotic strains globally.
• Bifidobacterium longum BB536: Associated with gut regularity, immune balance, and microbiome diversity in both adults and infants.
• Bifidobacterium infantis EVC001: Naturally found in infant guts; early supplementation of this strain through maternal milk may help establish beneficial infant microbiome populations.
• Lactobacillus reuteri DSM 17938: Linked to reduced colic symptoms and improved infant digestive comfort. Well-tolerated by both mother and baby.
• Lactobacillus acidophilus: A common and well-tolerated strain for general gut health and digestive balance in adults.

When reading supplement labels, look for the full strain name (genus, species, and strain designation) rather than just genus-level information. A product that lists only “Lactobacillus” without strain detail cannot be evaluated against the research.

Probiotic supplements are not the only source of beneficial bacteria. Fermented whole foods provide a diverse range of live cultures alongside other nutrients and are a natural complement to — or alternative for — supplement-form probiotics.

Probiotic-rich foods worth including in a breastfeeding diet:

• Yoghurt — specifically varieties containing live active cultures; full-fat, plain yoghurt is preferable
• Kefir — a fermented milk drink with a broader strain diversity than most yoghurts
• Miso — a fermented soybean paste used in soup or as a seasoning; also provides minerals and is warming and easy to prepare
• Sauerkraut and kimchi — fermented vegetables; choose unpasteurised varieties kept in the refrigerator (pasteurisation kills live cultures)
• Tempeh — fermented soybean cake; a useful protein and probiotic source, particularly for mothers following plant-based diets
• Kombucha — a fermented tea; moderate consumption is generally considered safe while breastfeeding, though the small alcohol content (typically 0.5–3%) means some mothers prefer to limit intake

For practical ideas on what to include in your daily eating during breastfeeding, the guide on foods to increase breast milk supply naturally covers nutritional priorities across the postpartum period.

Probiotics thrive when they’re supported by prebiotics — the dietary fibres that feed beneficial bacteria in the gut. Without adequate prebiotic fibre in the diet, probiotic bacteria (whether from food or supplements) are less able to colonise and thrive.

Good prebiotic food sources include:

• Oats (also a traditional galactagogue ingredient in lactation cookies)
• Garlic, onion, and leek
• Legumes and lentils
• Asparagus and Jerusalem artichoke
• Bananas — particularly slightly underripe
• Cashews and pistachios

Oats deserve a specific mention here: they’re both a prebiotic food and one of the most traditionally used ingredients in lactation support. Our evidence-based review of oats and milk supply covers how they fit into a breastfeeding nutrition plan.

Understanding what to avoid is as important as knowing what to take.

• Choosing by brand rather than strain: Marketing language around “gut health” is not a substitute for strain-specific evidence. Look for the full strain designation on the label.
• Expecting rapid or dramatic results: Probiotic effects build over weeks, not days. Consistency matters more than dose.
• Stopping probiotics when symptoms resolve: If you’re taking probiotics for a specific reason (post-antibiotic gut restoration, for example), stopping too early may mean the benefit doesn’t hold.
• Taking probiotics with very hot food or drinks: Heat can damage or kill live cultures. Take supplements at room temperature and wait before consuming very hot foods or beverages.
• Ignoring diet: Probiotic supplements work best alongside a diet rich in prebiotic fibre, diverse whole foods, and adequate hydration. A probiotic supplement will not compensate for a diet that actively disrupts gut health.

Assuming any probiotic labelled “safe for breastfeeding” is researched: Safety and efficacy are different things. A product may be generally safe without having evidence for the specific outcomes you’re looking for.

With dozens of products available in Australian pharmacies and online, here is a practical framework for choosing wisely:

1. Check the strain: Look for the full name (e.g. Lactobacillus rhamnosus GG, not just “Lactobacillus”). If the product only lists genus-level information, look for another option.
2. Check the CFU count: Most research has used doses between 1 billion and 10 billion CFU (colony-forming units) per day. Very high doses are not necessarily more effective.
3. Check for third-party testing: Choose products that list an expiry date with guaranteed CFU count at time of use (not manufacture), and ideally have been independently tested.
4. Check for allergens and additives: Some probiotic supplements contain fillers, gluten, dairy, or soy. If you’re managing a food-sensitive baby or following an elimination diet, read labels carefully.
5. Check storage requirements: Some strains are shelf-stable; others require refrigeration. Follow the storage instructions on the label to ensure live cultures remain viable.

As with any supplement during breastfeeding, it’s worth discussing your choices with a healthcare provider, particularly if you have any underlying health conditions or if your baby has health concerns.

If you’re also looking at herbal teas for breastfeeding support, the guide on herbal teas that are safe — and ones to avoid — while breastfeeding covers which herbs have good safety profiles and which to approach with caution.

For the complete picture of how nutrition supports milk supply and breastfeeding health, head back to the Breastfeeding Nutrition & Milk Supply: Evidence-Based Guide for Australian Mothers — where hydration, galactagogues, and the full nutritional framework come together in one place.

If you’re looking for practical, whole-food lactation support that complements your gut health efforts, browse the Nella Vosk range below.

Explore our lactation cookies — formulated with prebiotic-rich oats and evidence-backed galactagogue herbs, free from common allergens.

Or browse our breastfeeding teas — warm, nourishing, and formulated with herbs that have a good safety profile in lactation.

Also in this cluster:

→ 10 proven ways to increase your milk supply

→ Foods to increase breast milk supply: what the research says