Can microplastics in the environment disrupt the healthy bacteria babies get from breast milk?

What's actually in it

Microplastics are tiny plastic fragments smaller than 5 millimeters. They come from synthetic clothing fibers, food packaging, water bottles, and baby products like plastic breast pump parts and bottle components. They're now found in human blood, breast milk, and placental tissue.

Breast milk isn't just food. It carries beneficial bacteria that seed a newborn's gut and help train the immune system during the first months of life.

What the research says

A 2026 study in FASEB J found that polystyrene microplastics disrupt the vertical transmission of the breast milk microbiome. In plain terms, the good bacteria that should pass from mother to baby through nursing get scrambled.

The researchers found that microplastic exposure changed the mix of bacteria in breast milk. Key beneficial species like Lactobacillus were reduced, while less helpful bacteria increased. Babies who received this altered milk showed weaker early immune development and more gut inflammation.

The study also showed that the timing matters. Exposure during late pregnancy and early breastfeeding had the strongest effect, since that's when the bacterial transfer is most active.

You can't completely avoid microplastics, but you can reduce exposure during this critical window. Use glass baby bottles and breast milk storage containers instead of plastic ones. Avoid heating breast milk in plastic bags. And consider a silicone or glass breast pump setup if you're pumping regularly.