Can microplastics in a baby bottle make cow's milk harder for an infant to digest?

What's actually in it

Most baby bottles on the market are polypropylene (PP). When hot formula or hot water hits the inside, the bottle releases micro and nanoplastic particles straight into the milk. Earlier studies counted millions of particles in a typical prepared bottle. The open question was whether those particles do anything once they're in the baby.

Digestion matters in the first year. Babies' guts are still learning how to handle proteins. If something slows or changes digestion, it can trigger allergies, reflux, and poor weight gain.

What the research says

A 2025 study in Environ Pollut used a laboratory model of the infant stomach. The researchers mixed cow's milk with polypropylene micro and nanoplastics in the amounts known to come from heated baby bottles, then watched digestion unfold. The particles slowed protein breakdown, meaning intact or partially digested milk proteins stuck around longer. Larger protein fragments reaching the small intestine are one of the triggers for cow's milk protein allergy.

Nanoplastics had a bigger effect than larger microplastics because they stuck to the protein surface and blocked the enzymes from cutting.

If you're using plastic bottles, don't prepare or heat formula inside them. Warm the water in a glass or stainless container, let it cool below 70°C, and only then pour into the plastic bottle. Or skip plastic and use glass.