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 contains A1 beta-casein, which releases an inflammatory peptide called BCM-7 during digestion. A2 formula avoids this. The difference is one amino acid at position 67 of the protein chain, but the digestive consequences are measurable, particularly for infants with gut discomfort and colic.

It is 11pm. Your baby has been screaming for two hours. You have tried everything. Someone in a parenting group mentioned A2 formula and you are wondering if it is worth trying or just another thing that won't work.

Here is what you actually need to know: standard formula may be actively irritating your baby's gut in a way that A2 formula doesn't. There is a specific protein in most cow milk formulas that releases an inflammatory compound during digestion. Clinical trials show A2-fed babies cry significantly less and have better gut comfort. And the science behind why is genuinely fascinating once you see it.

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

Colic affects roughly 1 in 4 infants. 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 intestine often shows signs of inflammation, altered motility (things moving too slowly or in the wrong rhythm), and excess gas. The question is: what is triggering that?

For formula-fed babies, one answer may be sitting right in the tin.

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. One tiny difference. Enormous consequences.

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 peptide. It binds to opioid receptors in the gut lining - the same type of receptor that morphine binds to. The effect on the gut: motility slows down, transit time increases, mucus production goes up, and inflammation follows. In a newborn with a highly permeable gut lining, that gut inflammation does not stay local. It spreads. And for a baby who cannot tell you what is wrong, it comes out as screaming.

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 is softer and smaller. The gut processes it calmly, without the opioid-receptor activation that causes the inflammation cascade.

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 published in Frontiers in Nutrition put 120 infants on either an A2 beta-casein cow milk formula or a standard cow milk formula for four months, with a breastfed reference group for comparison.

At 60 and 90 days, the A2 formula group had significantly fewer hours of crying than the standard formula group - and their crying patterns looked like the breastfed group, not the standard formula group. They also had softer stools, more frequent bowel movements, less abdominal distension, and less gas. The A2 group's gut was simply working better.

Confirmed in mixed-fed infants too

A 2025 trial in Food Science & Nutrition tested 140 infants who were mixed-fed - receiving both breastmilk and formula. Half received A2 formula, half received standard formula. The A2 group showed improved gastrointestinal comfort scores and lower crying frequency. Even when breastmilk was part of the diet, the formula protein type made a measurable difference to how much the baby cried.

And presented at the biggest paediatric nutrition conference in 2025

At ESPGHAN (the European Society for Paediatric Gastroenterology, Hepatology and Nutrition) in May 2025, new data on 140 mixed-fed infants showed statistically significant improvements in gut comfort and fewer crying periods in the A2 group at weeks 2 and 4, with improvements continuing to week 8. Worth noting: this study was sponsored by The a2 Milk Company. Independent replication would strengthen the picture further.

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 has its own separate evidence base for eczema prevention on top of the gut comfort benefits. If you are dealing with both colic and skin issues, a whole goat milk formula covers both biological pathways. 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.

You are not grasping at straws. The science behind A2 formula and gut comfort is real. Whether it is the specific thing your baby needs is something only a proper trial will tell you.