X-Message-Number: 10639
Date: Sat, 24 Oct 1998 23:02:18 -0700
From: Brian Manning Delaney <>
Subject: Re: Biblical reference; CR
References: <>

To Thomas Donaldson,

I wrote a response to your comments on CR (summary thereof:
You're wrong. :), but then decided that I didn't trust my memory
of the articles you cited from the 70's, so I decided I'd look
them up before sending my response. More in a few days (at

Mike Perry <> wrote:


> It seems that CR increases maximum lifespan of
> mice--which means it might work for humans too.
> CR-mice live longer than controls, maximum as
> well as average. However, I've seen the claim
> that wild mice are naturally CR. Thus the "improvement"
> in lifespans that is seen amounts to the
> proposition that non-CR lab mice, who can have
> all they care to eat, don't diet right and thus *shorten*
> what is already their "natural" lifespan, if we
> factor out predation and diseases.

Thanks for bringing this point up.

Claims along these lines can take two forms: 1) CR'd rodents are
actually normal, and the AL (ad libitum) rodents are the abnormal
ones (the claim you mention). And 2) Regardless of the
determination of the normal point, non-obese humans are
"dietarily analogous" to CR rodents, and thus, cannot expect to
gain anything via CR.

These claims are both incorrect.

It's strange that gerontology researchers still make claim #1,
since someone familiar with the CR research (though not
necessarily anyone on this list, of course) should know one thing
that makes the claim obviously false: female CR rodents cannot
conceive, because they have amenorrhea. This is clearly not
natural. (Some species of rats do not always develop amenorrhea.)

Furthermore, the increase in longevity continues as rodents are
CR'd to increasingly severe degrees, ALMOST all the way to a
degree which causes death. It's unlikely that the typical intake
of food in the wild is so close to the border of an amount that
causes death. (Though rodents in the wild tend not to be obese,
to be sure, and some wild rodents may indeed be CR'd.)

In addition, many, if not most species of rodents need to be
caged individually, to prevent them from eating each other. (I no
longer make this point to bedmates....) Rodents in the wild
generally don't eat each other.

Finally, even if it WERE true that rodents in the wild are CR'd,
this point would have no bearing -- at least as far as an
understanding of aging-intervention is concerned -- on the
finding, repeated hundreds of times, that longevity is inversely
related to energy-intake (under otherwise health-promoting
conditions), up to a very severe restriction. Although:

Claim #2 MAY be true in a very limited sense. That is, it's
conceivable that the typical non-obese human is not dietarily
analogous to AL rodents, but to _slightly_ CR'd rodents. This
means, for a non-obese person considering CR, the expected life
span gain might need to be scaled down a little bit, but not
much, I'd guess.

Best wishes,
Brian Manning Delaney
(No need to CC articles to me.)

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