Formulas with partially hydrolyzed whey protein are the most widely recommended option for gassy babies. These formulas contain proteins that have already been broken down into smaller pieces, making them easier and faster for your baby’s immature digestive system to process. But the formula itself is only part of the picture. How you prepare it, what’s in it beyond protein, and whether gas is actually the problem all matter.
Why Babies Get Gassy in the First Place
A newborn’s digestive system is still developing. Compared to older children, infants have slower gastric emptying, limited intestinal motility, and lower levels of the enzyme that breaks down lactose. All of this means milk sits longer in the gut, where bacteria ferment undigested sugars and proteins, producing gas. For most babies, this improves steadily over the first few months as the digestive tract matures.
Swallowed air is the other major contributor. Babies gulp air during feeding, especially if the bottle creates a poor seal around their lips or if the formula itself is full of tiny bubbles from shaking. That air has to go somewhere, and when it moves through the intestines instead of coming up as a burp, it causes visible discomfort: a tight belly, pulling the legs up, squirming, and fussiness.
Partially Hydrolyzed Whey Formulas
Standard infant formulas use intact cow’s milk proteins, which are large molecules that take time to break down. Partially hydrolyzed formulas (sometimes labeled “comfort” or “gentle”) pre-split those proteins into smaller fragments. This speeds up gastric emptying, meaning the formula moves out of the stomach faster and spends less time fermenting.
In a clinical trial of 72 infants, those fed a partially hydrolyzed whey formula showed a 12.3% improvement in gastric emptying rate over four weeks, compared to 9.1% in the standard formula group. The same infants went from an average of about 7 daily regurgitation episodes down to roughly 3, while the standard formula group only dropped to about 5. Faster digestion means less gas buildup and less spitting up.
Common examples you’ll find on shelves include Enfamil Gentlease, Similac Total Comfort, and store-brand “gentle” formulas. These are a reasonable first switch if your baby seems uncomfortable on a standard formula.
Lactose-Reduced and Lactose-Free Formulas
True lactose intolerance is rare in infants, but some babies do produce less lactase (the enzyme that breaks lactose down) than others, especially if they were born early. When lactose passes through the small intestine undigested, gut bacteria ferment it and produce gas, bloating, and loose stools.
Lactose-free formulas replace lactose with another sugar, typically glucose or sucrose. If your baby has colic-like symptoms, a pediatrician may suggest trying a lactose-free formula as an early step. Many partially hydrolyzed formulas also reduce lactose content, so you may be addressing both protein and carbohydrate digestion with a single switch.
A2 Protein Formulas
Most conventional cow’s milk contains a mix of A1 and A2 beta-casein proteins. During digestion, A1 beta-casein produces a peptide fragment called beta-casomorphin-7, which triggers inflammation in the gut. A2-only formulas use milk from cows that naturally produce only the A2 protein, skipping that inflammatory byproduct entirely.
Research using MRI to track milk in the stomach found that conventional milk (75% A1, 25% A2) emptied faster than pure A2 milk. That sounds like a good thing, but rapid gastric emptying actually overwhelms the small intestine with undigested lactose, pushing more of it into the colon where bacteria produce hydrogen, methane, and carbon dioxide. The result is more gas and more discomfort. People who drank A2-only milk reported lower abdominal pain scores, and the slower, steadier digestion likely explains why.
A2 formulas (like Similac A2 or a2 Platinum) are worth considering if your baby seems uncomfortable on standard formula but doesn’t need a fully hydrolyzed option.
Formulas With Probiotics
Some formulas now include the probiotic strain Lactobacillus reuteri DSM 17938, and the evidence behind it for fussy, gassy babies is strong. A network meta-analysis found that this specific strain reduced daily crying time by an average of 51 hours over the study period compared to placebo, making it the most effective single intervention studied for infantile colic. In one trial, colicky infants given L. reuteri daily for 21 days went from a median of 370 minutes of crying per day down to just 35 minutes, compared to 90 minutes in the placebo group.
If you’re not using a formula that already contains this probiotic, it’s also available as standalone drops. Either way, the specific strain matters. Not all probiotics have the same evidence behind them for infant gas.
How You Mix the Formula Matters
Before switching formulas entirely, check how you’re preparing bottles. Vigorously shaking a bottle introduces tiny air pockets throughout the liquid. Your baby then swallows that aerated formula, and the trapped air contributes directly to gas.
Three simple changes can make a noticeable difference:
- Swirl instead of shake. Gently rotate the bottle in a circular motion until the powder dissolves. It takes a bit longer, but it produces far fewer bubbles.
- Stir with a clean utensil. A fork or small spoon works well for breaking up clumps without whipping air into the mixture.
- Let it settle. If you do shake the bottle, set it on the counter for a minute or two before feeding. Bubbles will rise to the surface and pop.
Using warm (not hot) water also helps powder dissolve more completely, leaving fewer undissolved particles that can create foam.
How Long to Wait After Switching
When you transition to a new formula, expect some temporary changes. Increased burping and gas typically last a few days as your baby’s digestive system adjusts. By around day five, most babies have adapted. If you’re switching gradually (mixing old and new formula together in increasing ratios), the full transition usually takes about a week.
Give any new formula at least one to two weeks before deciding whether it’s working. A single day of fussiness isn’t enough information. You’re looking for a consistent pattern: less straining, fewer episodes of visible discomfort, and a calmer baby during and after feeds.
When Gas Might Be Something Else
Garden-variety gas is uncomfortable but harmless. Cow’s milk protein allergy (CMPA) is a different story, and it can look similar in the early stages: fussiness, crying, feeding difficulties, and poor sleep. The key differences that raise the likelihood of a true allergy include blood or mucus in the stool, chronic diarrhea, eczema or other skin rashes, and a family history of allergic conditions.
If your baby has symptoms across multiple body systems (skin reactions plus digestive problems, for example), that pattern points more toward CMPA than simple gas. Babies with confirmed CMPA typically need an extensively hydrolyzed or amino acid-based formula, which is a step beyond the partially hydrolyzed “gentle” formulas discussed above. A pediatrician can guide a proper elimination trial to confirm the diagnosis before committing to a specialty formula.