Yes, more recent work indicates that just replacing the old blood plasma is enough to show the effect. See: https://www.aging-us.com/article/103418 https://www

Yes, more recent work indicates that just replacing the old blood plasma is enough to show the effect. See: https://www.aging-us.com/article/103418 https://www.aging-us.com/article/103418 (kudos to this journal for not being behind a paywall!) So, as you suggest, it now appears to be more a matter of "bad stuff" being in old blood rather than "good stuff" being in young blood. Apparently there is bad stuff that the kidneys, liver, etc. just cannot remove from the bloodstream, and this bad stuff builds up over time. I suppose one analogy might be that no matter how good your oil filter is, your car still needs an oil change once in a while.