Comment on CR mimetic drugs and nutraceuticals potential

From what I understand, iirc, CR works even outside the parameters that can ever be found in nature.   That is IIRC, even up to 65% restriction resulted in 65% increase in lifespan in mice.   It is extremely unlikely, virtually impossible, that on 65% restriction on a famine you will find extraordinarily micronutrient fortified food with minimal effort(as large effort will also result in death from excessive calorie burning from activity) as provided in the lab.
   
I've also heard that on CR started on adult organisms, the transition into CR needs to be gradual and not sudden to actually confer benefits.   The food also has to be fortified to provide sufficient micronutrients.   Again it would seem to be that famines might occur quite sudden and drastic, and may reduce micronutrient availability.

Even in the lab it may be that the mechanism could even go further if not for the low calories compromising vital functions.    On higher lifeforms like man the minimal calories necessary to not jeopardize function may be even higher(I've heard of some severe calorie restriction individuals losing bone integrity), but the genetic expression flexibility may still remain.

What will tell the true limits of these pathways are the physical limits in terms of gene expression that they can ever reach with interventions such as drugs or nutraceuticals.  Which may be reached at 65% CR or could be higher had it been physically possible to survive on even less calories.   CR mimetics stimulate the pathways without jeopardizing function from insufficient calories.

We now know that things like NAD+ drop with age in some organisms which may be behind why resveratrol failed on healthy organism with longer lifespans of a few years after succeeding in many organisms of lower lifespans such as yeast, c. elegans, fruit flies, and some short lived fishes.   Sirtuin dependence on NAD+ would obviously be compromised if NAD+ levels fall too low.Since resveratrol works in part through sirtuins it's effects would be adversely affected through such age associated changes.  But ways to increase NAD+ are now known, some readily available some on the horizon.

source Josh Mitteldorf scienceblog comment