Not all milk is the same: What you need to know

As kitchen all-rounders go, it’s hard to beat the versatility of milk. It’s the key to our coffee, plays a starring role in our bowl of cereal and is a secret weapon in everything from a weeknight pasta bake through to the kids’ birthday cake. With a bottle in the fridge, you can start the day with a cozy bowl of porridge, top up your tea or whip up a dinner-saving white sauce with ease.

But not all milk is the same. Different milks can vary in the nutrients and proteins they contain, which may influence both their nutritional profile and, for some people, their digestive experience. Here’s what you need to know.

You might already know that cow’s milk is a natural source of protein, the macronutrient we need for muscle growth and maintenance as well as helping us feel full after meals. But the nutritional benefits of cow’s milk aren’t limited to the grams of protein it provides.

Protein is made up of chains of amino acids – the “building blocks” used to grow and repair muscle, skin, hair and organs. Some protein sources, like certain nuts, legumes and grains, are low in some of the essential amino acids. But dairy milk offers a complete source of the essential nine amino acids that our body can’t produce on its own and must get from food, which is why dairy milk is considered a complete source of protein.

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You may not know that there are also important differences between cow’s milks. Cow’s milk actually contains two different kinds of milk protein: whey and casein. Whey digests quickly, which is why it’s so popular as a post-workout protein supplement. Casein digests slowly, supporting crucial functions like overnight muscle recovery. Both whey and casein serve important purposes in our body.

However, one subtype of beta-casein proteins, the A1-type protein may cause digestive discomfort in some people. Historically, all milk contained only A2 beta-casein protein. But a natural mutation caused the A1 protein to emerge and spread through dairy herds over time. Now, most dairy cows in Australia produce milk that contains both A1 and A2 type beta-casein proteins.

That’s most dairy cows but not all. a2 Milk® comes from cows specially selected to produce milk that naturally contains only the A2-type protein, and no A1 protein. a2 Milk may be a suitable option for those people who experience digestive discomfort when drinking regular milk but still want to reap the taste and nutritional benefits of dairy milk. Dietitian Kerri Segal says research suggests that A2 protein-only milk may be better tolerated by some people than ordinary milk.

Growing evidence is showing that milk containing only A2 beta-casein protein may be linked to better digestive comfort in some populations compared with ordinary milk.

For those people who experience digestive discomfort from ordinary milk, that might be more noticeable in the morning.