Wouldn't you know it. Two days after I get done trash-talking Nicotinamide Riboside (NR) as a supplement for health and longevity a new paper  (pop press article) comes out in the journal Science no less, apparently showing that NR supplementation extends lifespan in older mice by preventing their stem cells from turning senescent:
NR treatment of C57BL/6J mice slightly increased lifespan (chow diet, mean 829 ± 12.0; NR, mean 868 ± 12.4 days, p = 0.034) (Fig. 6G). The beneficial effect of NR on survival was further confirmed by Cox proportional hazards analysis (Fig. 6H). Although the lifespan benefit is small, it was obtained with the NR treatment commencing late in life at 24 months.
Here are the two survival curves for the NR-treated and control mice, in terms of how many days they lived after the treatment with NR (or placebo) began:
While there was a nominal difference between the two groups' median
lifespans, both groups' median lifespans were still well within the normal zone for healthy mice. More significantly, while the authors don't report maximum
(tenth-decile) survivorship (an increase in which relative to normal, healthy controls is the sine qua non
of an anti-aging intervention), you can see right from the survival curves that this doesn't cut it: the very last control animal died at age ≈960 days (700 days (see legend to Figure 6) + an eyeballed 260 d from the graph)), and the last treated
animal died at age ≈1010 days: ie, the controls were abnormally short-lived, and the treated animals on the low side of normal. This is already clear just from looking at the shape of the survival curve itself, which is clearly not rectangular: from ≈850 days onward, both
groups were clearly suffering high death rates from middle age onward. It would have been nice to have been able to see the survival curves throughout the adult LS instead of just from initiation of treatment to see how exactly those normal-seeming median LSs could coexist with such relatively rapid death rates. Irrespective, this is obviously very unconvincing as a lifespan study.
Here are some more impressive graphs from the full text, showing NAD+ was increased in both young and aged mice treated with NR, both groups had more viable muscle stem cells, ran longer and farther (when facing threat of shock), and had higher grip strength than controls
The question is whether this would manifest in animals that weren't, apparently, rapidly failing in health starting from relatively early in the equivalent of human 60-70 year olds.
I should, however, say that the evidence supporting the benefits of NR certainly look better today than they did at the time I wrote my post for the SENS Research Foundation Blog. There's now evidence
that NMN can work
after oral administration, and the same study reported finding elevated NMN in plasma following oral gavage — and appeared to show benefits in aging mice. And a recent detailed study of NR and NMN metabolism
seems to suggest that any benefits found in NMN should be translatable to NR.
The fact that all of these studies involve such extremely high doses, however, remains a significant question mark for people actually using the stuff and not ready to take such extremely high doses or shell out so much money to do so. And as noted above, I'd strongly urge caution about using the much cheaper and better-studied niacin as a companion NAD booster to NR.
 Science. 2016 Apr 28. pii: aaf2693. [Epub ahead of print]
NAD+ repletion improves mitochondrial and stem cell function and enhances life
span in mice.
Zhang H(1), Ryu D(1), Wu Y(2), Gariani K(1), Wang X(1), Luan P(1), D'Amico D(1),
Ropelle ER(3), Lutolf MP(4), Aebersold R(5), Schoonjans K(6), Menzies KJ(7),