Douglas Skrecky has cited a pilot study made with 17 controls and 18 calorie-restricted rats (who were also subject to protein restriction) and then goes on to say:
> 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.
Douglas is evidently unaware of the work by Drs. Weindruch and Walford. These men have made themselves the foremost names in Caloric Restriction research by the extreme care they have taken to ensure Adequate Nutrition and good care of laboratory animals (including ensuring that animals cannot eat their own shit). In particular, they have made ground-breaking discoveries concerning the benefits of Caloric Restriction with Adequate Nutrition (CRAN) begun in adulthood.
As an example, I cite Study 1 on Table 2.7 of THE RETARDATION OF AGING
AND DISEASE BY DIETARY RESTRICTION by Richard Weindruch and Roy Walford
(1988). This study involved 68 control mice and 67 CRAN mice (consuming
60% of the number of calories of the controls). A comparison was made
between controls, Adult Dietary Restriction [(ADR) initiated at 14 months]
and Early Dietary Restriction [(EDR) initiated at 1 month]. The results:
Average Lifespan Maximum Lifespan (months) (months) Control 36 41 ADR 39 45 EDR 43 50
Taking 115 years as the human maximum lifespan, the ADR animals began their CRAN at the equivalent of 39 years of age and lived about 10% longer.
Douglas latches on to age 45 as the age at which CRAN can no longer be of benefit. What does he think happens between 39 and 45, some kind of "aging menopause"? No, human physiology does not change that much with aging.
In my opinion, the benefits of CRAN are mainly due to: (1) reduced free-radical oxidation damage and (2) reduced non-enzymatic glycosylation. I believe that these benefits can be had at almost any age. The earlier the better (after development), but I think its never too late to get some benefit (provided CRAN is applied in a non-traumatic manner).
Mice and humans are different, of course. CRAN is most beneficial when begun before puberty, but by my calculations 1 month for a mouse corresponds to 2.8 years for a human. Few humans reach puberty at this age. More seriously, I think that the benefits of CRAN for average lifespan are much greater for humans than for mice. Humans are more vulnerable to cardiovascular disease, which cuts an average of 14 years from life. Moreover, the number one risk factor for stroke is high blood pressure and the best way to lower blood pressure is to lose weight. Since I began practicing CRAN I have had a significant decline in my resting blood pressure and heart rate. There may be yet another benefit insofar as a major cause of senile dementia is sub-clinical strokes.
I believe that we are on the cusp of radical breakthroughs in the
capacity of science to stop aging and achieve suspended animation of
the brain. If I can extend my life even an additional 5%, that may be
the difference between gaining these benefits or "missing the boat".