03/09/2026
One of the coolest things about breast milk is that it isn’t made from the contents of your stomach. It’s made from your blood. Your mammary glands act like tiny, very sophisticated filters that pull nutrients, water, fats, sugars, and proteins from the bloodstream and turn them into milk. That means when you eat something with protein (like dairy, soy, eggs, etc.), the protein itself doesn’t just “fall into the milk.” First it’s digested, broken down into amino acids, absorbed into your blood, and then small pieces of those proteins can pass into milk. Because of that process, it usually takes a few hours for dietary proteins to show up in breast milk, and they gradually clear from the milk over about 24 hours or so after you stop eating them. For most babies this is completely fine. But some babies have immature or sensitive digestive systems and can react to certain proteins, most commonly cow’s milk protein, which can lead to symptoms like gassiness, mucus in stools, reflux-like discomfort, or fussiness. It’s not because the milk is “bad”, it’s just the baby’s gut saying, hey, this protein is tricky for me right now. The good news is that as babies grow and their digestive systems mature, many of these sensitivities improve over time. 💛