X-Message-Number: 6187
Date: Sat, 11 May 1996 18:12:32 -0700 (PDT)
From: Doug Skrecky <>
Subject: Is Late-Life Caloric Restriction Beneficial? (fwd)

Cryonetters might find this an interesting read.  -Doug

---------- Forwarded message ----------
Date: Sat, 11 May 1996 18:10:37 -0700 (PDT)
From: Doug Skrecky <>
To: 
Cc: 
Subject: Is Late-Life Caloric Restriction Beneficial?

   I have finally been able to obtain a copy of "Is Late-Life Caloric
 Restriction Beneficial?" Aging Clin. Exp. Res. 136-139 Vol.7 1995
 My own analysis of this is as follows: Lifespan was compared between 17
 ad libitum fed Long Evans rats with a group of 18 rats gradually
 introduced to a 33% calorie restriction in calories begining at 18 months
 of age. Diets were stated to be sufficient to provide micronutrients in
 excess of requirements in both groups. However instead of eliminating
 some of the carbohydrate to provide a restricted diet, a 33% restriction
 on Agway 3000 chow was used so the experiment was actually a combination
 of a 33% calorie restriction and a 33% protein restriction. 
   At 30 months of age, 8 of 17 ab libitum rats and 11 of 18 restricted
 rats had died. Mortality was lower (47%) in ab libitum than in (67%)
 restricted rats. Average lifespans were roughly 900 days and 810 days
 respectively. (For a comparison see table below reproduced from a
 previous posting)
   My own conclusions are somewhat tentative since this was a pilot study. 
 The most damaging criticism is that the restricted rats were deprived of
 33% of the protein fed to the ab libitum rodents. This is a defect in the
 study which seriously undermines any conclusions, which might be derived
 from it. However be that as it may, this experiment is in line with
 others which have failed to obtained any lifespan extension in older
 animals. NO EXPERIMENT TO DATE HAS EVER OBTAINED A LIFESPAN EXTENSION
 WHEN CALORIE RESTRICTION WAS INITIATED IN EITHER LATE OR MIDDLE AGE. If
 the same holds true for humans then three conclusions can be drawn given
 that 18 months in Long Evans rats corresponds roughly to 18/30 * 75 = 45
 years in human terms. 

 #1.  Humans older than 45 years will not extend their lives by initiating
 caloric restriction except by a reduction in disease risk. An "AN" diet
 rather than a CRAN diet would here be more appropriate. 

 #2.  Calorie restriction initiated in younger animals is MORE EFFECTIVE
 than was hitherto realized since all of the lifespan extension achieved
 was due to restriction over a more limited time frame. Humans younger
 than 45 years have an added incentive since full benefits of CRAN are
 obtained with a restriction over a shorter time period - up to 45 years
 of age. 

 #3.  As the table below shows humans seeking to extend their lives would
 be well advised to pay more attention to life extending supplements
 rather than to dietary changes. Chromium picolinate for instance appears
 to be far more effective than calorie restriction in Long Evans rats. 

    GROUP       AVERAGE OLDEST
  OF RATS      LIFESPAN LIFESPAN
 A: controls        875 1200
 B: exercised       978 1208
 C: 30% restricted 1056 1322 (same weight as B)
 D: exercised &     995 1328
    30% restricted
 E: 46% restricted 1088 1341 (same weight as D)
 F: chromium       1320 1440
    supplemented


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