The article of Silva et al. (2024) on the carbon (C) footprint of milk production in the São Paulo state in Brazil has raised our attention. The authors included the C uptake during photosynthesis, without taking into account the subsequent C release during livestock production and during the consumption of the food products. We thank the authors for putting forward this highly relevant topic. However, we consider this approach as incomplete, leading to a biased assessment and finally to misleading conclusions. As this is a commonly debated issue, we use the example of the dairy systems analysed by Silva et al. (2024) to illustrate the problematic of ignoring the temporary characteristic of the C storage during photosynthesis.