title: Revised Estimates for the Number of Human and Bacteria Cells in the Body.
abstract: Reported values in the literature on the number of cells in the body differ by orders of magnitude and are very seldom supported by any measurements or calculations. Here, we integrate the most up-to-date information on the number of human and bacterial cells in the body. We estimate the total number of bacteria in the 70 kg "reference man" to be 3.8·1013. For human cells, we identify the dominant role of the hematopoietic lineage to the total count (≈90%) and revise past estimates to 3.0·1013 human cells. Our analysis also updates the widely-cited 10:1 ratio, showing that the number of bacteria in the body is actually of the same order as the number of human cells, and their total mass is about 0.2 kg.
authors.affiliation: Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Ron
authors.identifier: 0000-0002-1165-9818
authors.initials: R
authors.lastname: Sender
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Shai
authors.identifier: 0000-0002-7642-6556
authors.initials: S
authors.lastname: Fuchs
authors.affiliation: Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Ron
authors.initials: R
authors.lastname: Milo
mesh_terms: D000328:Adult; D001419:Bacteria / Q000166:cytology / Q000254:growth & development*; D058491:Bacterial Load; D001837:Body Weights and Measures; D002452:Cell Count; D006801:Humans; D008297:Male; D064307:Microbiota; D009928:Organ Specificity