What is A2 Formula?
The protein science, the colic evidence, and how to choose.

A2 formula is infant formula made from cow milk containing only the A2 beta-casein protein, or from goat milk, which is naturally 100% A2. Standard cow milk formula also contains A1 beta-casein, which during digestion releases a peptide called BCM-7. A2 formula doesn't. The two variants differ by a single amino acid at position 67 of the protein chain, and a growing body of research suggests that small difference may matter for how comfortably some babies digest their formula.

If you've ended up here, you've probably already spent time in the formula aisle reading labels that all sound the same, or scrolling parenting forums where A2 comes up as the thing that "fixed" someone's colicky baby. It's a fair question whether it's worth trying or just another dead end. Here's what the actual evidence says.

First: what is actually happening inside a colicky baby's gut?

Colic affects somewhere around 1 in 5 infants, though estimates vary widely depending on how strictly it's defined. Doctors define it as crying for more than 3 hours a day, more than 3 days a week, for more than 3 weeks in an otherwise healthy baby. Nobody fully understands it - which is why there is no single cure.

But one of the leading theories involves the gut. A colicky baby's gut often shows signs of inflammation, altered motility, and excess gas — which raises the question of what's setting that off in the first place.

For formula-fed babies, one possible trigger is the formula itself — specifically, the type of protein in it.

The protein your formula contains - and why it matters

Cow milk contains a protein called beta-casein. There are two main versions: A1 and A2. They differ by a single amino acid at position 67 of the protein chain - histidine in A1, proline in A2. It is a small structural difference, but it changes how the protein behaves during digestion.

When a baby digests A1 beta-casein - which is in most standard formulas - that single amino acid difference means the protein gets cleaved in a specific way. It releases a peptide called BCM-7 (beta-casomorphin-7).

BCM-7 is an opioid-like peptide that can bind to opioid receptors in the gut. In laboratory and animal studies, and some adult human studies, this has been associated with slower gut motility, more mucus, and markers of inflammation. The hypothesis is that in some infants this contributes to the discomfort and crying seen in colic. It is important to be clear that this is a leading hypothesis, not a settled chain of cause and effect in human babies — the infant evidence is still limited.

When a baby digests A2 beta-casein - the proline at position 67 forms a bond that is resistant to that specific cleavage. BCM-7 is not released. The curd formed in the stomach also tends to be softer and smaller. The idea is that without the BCM-7 pathway in play, there's less of the gut irritation described above — though, again, that's the proposed mechanism rather than a proven one.

Goat milk is naturally 100% A2 beta-casein - it does not carry the A1 variant at all. Some cow milk formulas are now made from A2-only dairy herds. Both avoid BCM-7 entirely.

What the clinical trials show

A 2024 randomised, double-blind, controlled trial in Frontiers in Nutrition followed 120 infants for four months, with a breastfed reference group. One important detail: the A2 formula in this trial also contained casein phosphopeptides and high sn-2 palmitate, while the standard formula had neither. So the two formulas differed in three ways, not just the beta-casein variant — meaning the benefits can't be attributed to A2 alone.

At 60 and 90 days, the A2-formula group cried significantly less than the standard-formula group and had softer stools, more frequent bowel movements, and less abdominal distension and gas. Because of the formula differences noted above, the trial shows that this particular A2 formula outperformed this particular standard formula — not that A2 alone was responsible.

A second trial, in mixed-fed infants

A 2025 trial published in Food Science & Nutrition - and presented the same month at ESPGHAN, the main European paediatric gastroenterology conference - followed 140 mixed-fed infants on an A1-free formula against 140 on a standard formula. The A1-free group had better gut-comfort scores (measured by the IGSQ questionnaire) and fewer daily crying episodes at weeks 2 and 4, with improvement continuing to week 8.

Two things to weigh here. The study was funded by The a2 Milk Company. And the conference presentation and the journal paper report the same trial, not two separate results - so this is one additional study, not two. Independent, non-industry replication would strengthen the picture.

Which A2 formulas are actually available

A2 formula comes in two fundamentally different forms. The first is A2-only cow milk formula, made from cows selectively bred to produce only the A2 beta-casein variant. The second is whole goat milk formula, which is naturally 100% A2 because goats have never carried the A1 variant.

A2-only cow milk formulas

Holle A2 (Swiss, EU organic certified) is the most widely available A2 cow milk option in Europe and the US import market. It uses organic milk from Demeter biodynamic farms and offers stages 1 through 3.

Serenity A2 is a US-based option, positioned around clean-label ingredients. Happy Baby Organic A2 is another US option, from the Happy Family brand.

The a2 Milk Company's a2 Platinum is the Australian market leader and the original A2-only formula brand, though availability outside Australia and New Zealand is limited.

Whole goat milk formulas (naturally A2)

Goat milk formulas are naturally A2, which is why they appear in the colic and gut-comfort research alongside A2-only cow milk formulas. Widely available options include Holle Goat (Swiss, organic), Jovie Goat (Dutch, organic), Pure Goat (Dutch, organic), Kendamil Goat (UK), and Nannycare (UK brand, New Zealand manufactured).

For parents in the US and Europe, the most reliably available and EU-certified-organic options are typically Holle A2 (cow), Holle Goat, Jovie Goat, and Pure Goat. Our full formula guide goes through the brand-by-brand differences in more detail.

Three things to be clear-eyed about

Colic has more than one cause. The A1/BCM-7 pathway is one credible gut-inflammation route - not the only one. If your baby's colic is driven by gut microbiome imbalance, lactase deficiency, or something else entirely, changing the beta-casein variant in their formula won't fix it. That does not mean it is not worth trying - it means have realistic expectations and a 2-4 week trial window.

A2 formula is not the same as hypoallergenic formula. If your baby has a confirmed cow milk protein allergy - symptoms like hives, vomiting, wheeze, or blood in stools after feeding - do not switch to A2 cow milk formula. It still contains all the other cow milk proteins that trigger allergic reactions. A2 only addresses the beta-casein variant. For confirmed allergy, you need an extensively hydrolysed or amino acid-based formula prescribed by a paediatrician.

Goat milk formula is also naturally A2 - and some parents choose it hoping for skin benefits as well as gut comfort — though the eczema evidence specifically is weaker and more mixed than the gut-comfort research. See our article on goat milk formula and eczema for the full research breakdown.

How to choose an A2 baby formula

Check your current formula. Look at the ingredients. If it lists "skimmed cow milk," "whey protein," or "whole cow milk" without specifying A2, it almost certainly contains A1 beta-casein. That is the starting point.

Switch to A2 or whole goat milk formula. Look for either "A2 beta-casein" or "whole goat milk" on the label. European-approved options (EFSA-certified) have the most rigorous safety standards, particularly in light of the 2025-2026 formula supply chain events, which highlighted how regulatory architecture matters for formula safety. Give it a minimum of two weeks - gut adjustment takes time and a one-week trial is not long enough to draw conclusions.

Keep one variable at a time. Do not switch formula and introduce solids or change feeding schedule simultaneously. You want to be able to attribute any change to the formula switch.

If it does not help after 4 weeks, go back to your GP or paediatrician. There are other routes worth investigating - including probiotic supplementation (Lactobacillus reuteri DSM 17938 has the strongest evidence for colic specifically), lactase drops if lactose sensitivity is suspected, and in some cases extensively hydrolysed formula.

This isn't a long shot. The research linking A2 formula to better gut comfort is real, if still developing — and a careful 2–4 week trial is the only way to find out whether it's the thing your baby needs.