Do plastic baby bottles release microplastics that interfere with formula digestion?
Yes. Polypropylene microplastics from plastic bottles impair how infants digest cow's milk proteins.
What's actually in it
Most plastic baby bottles are made from polypropylene (#5 plastic). During shaking, heating, and sterilizing, polypropylene sheds microscopic particles into the formula or breast milk inside. Infants then drink the particles with every feeding.
Once in the gut, those particles don't just sit there. Digestion is an active process, and the particles interact with digestive enzymes and the proteins in the milk.
What the research says
A 2025 study in Environ Pollut tested how polypropylene microplastics from plastic bottles affected the digestion of cow's milk proteins under infant gut conditions. The microplastics impaired the digestion of cow's milk proteins. Proteins that should be broken down into absorbable amino acids were less efficiently processed in the presence of plastic particles.
If a baby can't fully digest their formula proteins, that affects both nutrition and gut immune development. This adds a direct nutritional harm on top of the toxicological concern.
Glass baby bottles eliminate this entirely. Glass baby products don't shed microplastics, don't interfere with formula, and can be sterilized without releasing chemicals into the milk.
The research at a glance
| Study | Journal | Year |
|---|---|---|
| Polypropylene micro- and nanoplastics affect the digestion of cow's milk proteins in infant gut conditions | Environ Pollut | 2025 |
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