Probiotics have been more heavily marketed in the health food space over the past few years for their role in gut health, but prebiotics are equally important. Here's the difference:

Prebiotics

Prebiotics are non-digestible food fibers that encourage the growth of beneficial bacteria in the gut.¹ They are naturally found in certain foods like fruits, vegetables, and whole grains. In baby formula, prebiotics are added to mimic the beneficial components found in breast milk that support the growth of healthy gut bacteria.²

Prebiotics are what the naturally present good bacteria in the gut feed on. Therefore, prebiotics help create an environment in the gut where good bacteria can thrive. In turn, healthy gut flora supports your baby’s digestive system function.

Probiotics

While prebiotics are food for bacteria, probiotics are the actual live, good bacteria.¹ They are often referred to as “friendly bacteria” because they help balance the gut flora by promoting the growth of beneficial bacteria while preventing harmful bacteria from thriving.

Probiotics are naturally found in foods like yogurt and fermented foods, but many baby formulas now contain added probiotics to support a healthy balance of gut bacteria. These probiotics can help with digestion and may reduce the likelihood of digestive discomfort, such as constipation, by softening stool.²

During the first year of life, a baby's digestive system is still developing. Breast milk and formula are both perfectly designed to support this development and ensure that all infant nutrition requirements are met. One key difference, however, is that breast milk naturally contains prebiotic oligosaccharides and a small amount of probiotics, while the average infant formula does not. 

Prebiotics and probiotics are not required by the USDA to be added to infant formula, and formulas without these additions are still considered nutritionally complete. Formulas that do contain these additions are. however, considered completely safe.

If you are considering buying a formula that includes these ingredients, here are some potential benefits they offer: 

Supporting a Healthy Gut

Ingredients like prebiotics and probiotics in infant formula are designed to encourage the growth of beneficial bacteria and help mimic some of the microbiome patterns seen in breastfed infants. Research has shown consistently that infant formula with probiotics and prebiotics often leads to softer stools, lower stool pH (a signal of a healthy gut), and increased levels of beneficial bacteria.³

Strengthening the Immune System

Breastfed babies have higher levels of Bifidobacteria, which are considered beneficial bacteria. Lower levels of Bifidobacteria are linked to weaker gut barrier function, higher stool pH, and greater risk of inflammation, which may affect immune development.² Formulas supplemented with this strain of probiotic can therefore help support a gut microbiome more similar to that of breastfed babies. 

Enhancing Nutrient Absorption

Research suggests certain prebiotics can help improve the absorption of minerals such as calcium, magnesium, and possibly iron, likely by changing the gut microbiota, increasing short-chain fatty acid production, and lowering intestinal pH to make those minerals easier to absorb.⁴

Prebiotics and probiotics are considered completely safe ingredients to add to infant formula. Depending on the brand, range, and stage, a variety of probiotics and prebiotics may be used. 

The prebiotics most commonly used in baby formula are: 

• GOS (galacto-oligosaccharides), which are typically derived from lactose, the natural sugar found in milk (usually cow’s milk). Through an enzymatic process, lactose is converted into short chains of sugars that beneficial gut bacteria can feed on.
• FOS (fructo-oligosaccharides), which are usually derived from plant sources, most commonly chicory root, but also from foods like onions, garlic, and bananas.⁵

Different strains of probiotics offer different benefits, and the amount added is also important. Unlike adult probiotic supplements, baby formulas often use one or two strains, not a full microbiome range. Most probiotics used in baby formula are originally isolated from natural human or food-related sources, then grown in controlled lab conditions for safety and consistency.

• Bifidobacterium strains - The most common strain seen in baby formula, and Bifidobacterium lactis (Bb-12), breve, longum subsp. infantis (B. infantis) are what you may see listed on the packaging. These are the most widely used because Bifidobacteria dominate the gut of breastfed infants and are linked to gut and immune development.
• Lactobacillus strains - You may be more familiar with these strains, as they show up in adult foods like yogurt. On an infant formula ingredient list, you may see Lactobacillus rhamnosus GG, reuteri DSM 17938, or fermentum (CECT5716). These are often included for digestive support and potential immune benefits, though effects vary by strain.²

Check the Ingredients
Look for formulas that list blends of prebiotics and probiotics on the label to ensure optimal infant nutrition. Common prebiotics include GOS and FOS, while common probiotics are Lactobacillus and Bifidobacterium.

Consult Your Pediatrician
Your baby’s unique needs may require specific guidance when choosing a formula. Speak with your pediatrician to find out which type of formula will be best for your baby’s digestive health.

Look for a Formula That Supports Both Gut Health and Immunity

Some formulas not only contain prebiotics and probiotics but also include additional nutrients like DHA and ARA to support brain and eye development in infants fed on formula. These added ingredients can help provide well-rounded nutrition for your baby.

Consider Sensitivities

If your baby has sensitivities or allergies, consult with your pediatrician to make sure the formula you choose is appropriate for their needs.

Prebiotics and probiotics are naturally found in breast milk, and some baby formula producers add these to mimic the composition of breast milk. It is not required for baby formula in the United States to contain probiotics or prebiotics, but these additional ingredients are completely safe for your child and may offer several benefits that standard formula lacks. Depending on the stain and amount, these naturally derived ingredients can provide developing digestive system support, strengthen immune health, and improve nutrient absorption. More research, however, is needed to confirm the long-term health benefits of prebiotics and probiotics in baby formula. Always consult your pediatrician if you have any doubts about what formula is best for your baby.