Cells are, of course, replaced all the time [0]. For example, certain white blood cells every 2-5 days. In general metabolic processes slow down when fasting.

Cells are, of course, replaced all the time [0]. For example, certain white blood cells every 2-5 days. In general metabolic processes slow down when fasting. Immune cell replacement doesn't reset your immune system; that would be a very bad thing, no? You'd suddenly lose all resistance to everything you'd been exposed to or vaccinated against. A quick internet search shows a PR piece from USC, "Fasting triggers stem cell regeneration" [1]. I'm not impressed. The article says "it is the first evidence of a natural intervention triggering stem cell-based regeneration of an organ or system," implying no previous study has ever shown such an effect, and it certainly isn't generally accepted as a biomedical effect. I don't know if the study results have been replicated. What the study's actual data said was "long periods of not eating significantly lowered white blood cell counts," which in mice was followed by a rebound when fasting ending. The researcher's interpretation was that he "likens the effect to lightening a plane of excess cargo." [Yeah! Let's temporarily get rid all those pesky unneeded white blood cells!] So my interpretation is that the white blood cells died off after a few days, as normal, and fasting interfered with their replacement. Fasting stopped, and replacement recommenced. I don't really get the popularity of quackish theories about fasting, "cleanses," etc. There's already a perfectly good regeneration system--it's called sleep. I guess it's like weird ideas about "oxygen-free copper" and such in audio circles. It's something to tweak, feeling like you're going above-and-beyond, but without actually being too difficult. [0] http://book.bionumbers.org/how-quickly-do-different-cells-in-the-body-replace-themselves/ http://book.bionumbers.org/how-quickly-do-different-cells-in... [1] https://news.usc.edu/63669/fasting-triggers-stem-cell-regeneration-of-damaged-old-immune-system/ https://news.usc.edu/63669/fasting-triggers-stem-cell-regene...