In mice, approximately 40% of white blood cells are destroyed during a four-day fast and are rebuilt within a few days of refeeding.

“So, during starvation, whether you're a mouse, and now we know the same to be true for people, you have to get rid of a lot of cells, a lot of things that you don't need. And that's what's happening, it's not so much about autophagy, but it's more about apoptosis, and so, a program cell diet. You're killing, essentially giving rid of a lot of cells, and then you stand by, you wait until food comes around again, and you rebuild it. So, for example, in a mouse, about 40% of the white blood cells are destroyed during this period of four days of fasting or so.”

“And then, that 40% is rebuilt within a few days of refeeding, right? So, it's really extraordinary and probably the most powerful regeneration or generation program that you have since birth, essentially, right?”

“For example, if you're looking at autophagy or apoptosis that's happening, you may not see or be able to even measure it. Maybe it's happening, but you can't really measure it well until you're getting a more prolonged fast, like when you don't eat for four days.”

“And it is a way to adapt the repertoire of immune cells to changing circumstances. It is a way also to inhibit unwarranted inflammatory reactions.”

“And certainly of course we are also very interested in, is there preferential killing of the damaged cells? And we've started to show that in our multiple sclerosis mouse model, and also the human study, there was evidence that the white blood cell level temporarily was reduced during the, at the end of the fasting cycles and then went back to normal.”