TABLE 2.

Frequently heard statements and rebuttals on FBS use.

Statements (why FBS is still used)	Rebuttals (why FBS should be abolished)
It is cheaper	Prices for FBS fluctuate considerably (RMBIO, 2016), especially depending on quality. In contrast, production of animal-component-free materials will be more independent from agricultural supply chains, and upscaling will inevitably reduce their prices
It is convenient	Using FBS in cell culture includes pre-testing of FBS batches to check for their suitability, which is inconvenient and expensive at the same time. In contrast, chemically defined supplements are defined and need no laborious batch-testing
This is how it has always been done	Scientific progress lives from new inventions and ideas. Otherwise, it devolves to mere maintenance. So, do not be afraid of innovations
Never change a running system	Is the system running, though? Batch-to-batch variability can prevent it from running at all the next time (Weber et al., 2022). In addition, products used for therapeutic applications will most likely not get regulatory approval when they contain FBS.
Switching to serum-free medium prevents direct comparison with results generated under FBS conditions	Cells will behave differently when changing the culture medium. However, results in FBS-supplemented media would only be comparable when using the same FBS lot (Barosova et al., 2021), but this lot might not be available for later experiments. Thus, the possibility of comparing experimental results of cells grown in FBS-supplemented media is questionable
It is unclear how replacing FBS affects the physiology of the cells	Using FBS in the first place is in fact affecting the physiology of cells, this is just either ignored or overlooked. Serum-free cell culture media can provide a much more physiologically controlled environment
With FBS, the cells grow faster	This is another result of the unphysiological environment of serum-based medium. Slower growth might just be closer to how cells grow in the body
The test guidelines must be followed	Unless the regulated and validated processes are changed, this is unfortunately the case. However, regulators are willing to accept changes that demonstrate the same or even better results and improved reproducibility (Perez-Diaz et al., 2023; Reichstein et al., 2023)
There are no better materials available	This publication presents many better materials. In case you do not find a suitable material or strategy for you to switch to, consider consulting the following resources (Bartnicka et al., 2021; Berg and Kurreck, 2021; Duarte et al., 2023; Rafnsdóttir et al., 2023; Reichstein et al., 2023; Bramwell et al., 2024; Weber et al., 2024; 3Rs Centre Utrecht, 2025)