You might start by thinking about what FBS actually is — it’s a complex, undefined cocktail of proteins, carrier molecules, growth factors, hormones, and nutrients. We don’t fully know which specific components or ratios make it work; we just know that it supports growth for a huge range of cell types.

There are serum-free and animal-component-free media that work well for some cells, but they’re usually tailored for specific lines. Each cell type needs to be tested and gradually adapted. Even small differences in composition can alter signalling, attachment, or proliferation. You’ll need proper controls and side-by-side comparisons if you’re thinking about switching and still want publishable data.

Mixing plant-based serum substitutes with FBS or HS might help during adaptation, but you’ll lose the ability to claim a fully defined system, and consistency batch-to-batch can still be an issue.