Researchers at the Weizmann Institute of Science in Israel combined data on the size, abundance and typical lifespan of every major human cell type into a single running total.
The calculation came to about 330 billion cells replaced every day, roughly 80 grams of cellular mass, more than a large chicken egg weighs. Blood cells made up close to 90 percent of the cells replaced, while blood and gut lining cells dominated the mass.
The figure is an estimate built by combining many smaller studies rather than one direct measurement, and the authors note real uncertainty in some of the underlying numbers for less-studied tissues. Still, it gives a concrete sense of how much continuous rebuilding keeps a person's cell count roughly stable even though individual cells are constantly dying and being replaced underneath that apparent stability.
Read the original study
Sender and Milo, Nature Medicine, 2021 · doi.org/10.1038/s41591-020-01182-9
330 billion replacements, every single day.
Source
- Sender, R., & Milo, R. (2021). The distribution of cellular turnover in the human body. Nature Medicine, 27(1), 45–48. https://doi.org/10.1038/s41591-020-01182-9