Benefits of 40% CR with 1% Restriction (????) Part 1. The Papers

[Guest guest]

Hi folks:

I am afraid this is gonna be a long post. So long, that I am gonna

have to post it in five sections. It started out as a short post.

But the initial version raised more questions than it answered. That

led to additions which raised more questions. I could add more, but

I have spent much too much time on this already. So here it is, for

what it is worth. Please excuse the fact that this is not as well

organized as I would like, and no doubt contains some repetition.

I have just had what seems like a revelation, at least to me, about

nutrition. Hopefully I will not find out that everyone else has

known all about this for years, although I do recall a brief

discussion of the issue here some time ago which I perhaps didn't see

the significance of at the time. This is causing me to make the

biggest shifts since 1974 in my beliefs about what constitutes the

healthiest diet

This post has arisen from an offlist conversation with our veritable

Dr. Pater - a mine of fascinating information - in which he

straightened me out about a couple of important issues. I suggested

he post about it, but he said he preferred that I do so. So you can

blame him for the content of this post! And especially for any

spelling mistakes I make writing it ;; ^ )))

What this post reports is, frankly, a bit difficult to believe.

Indeed, perhaps it is too good to be true. But, as usual, the

approach will be to report study findings (always with the

reservation that, not infrequently, the next study on the exact same

topic may show precisely opposite results (!) ), and then draw the

conclusions that seem to be appropriate. The definitive answer to

this question will not be available for a very long time.

Nevertheless I am already starting to make fundamental, and in some

cases startling, shifts to my eating habits in response to what the

papers referenced below appear to be saying.

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I had emailed Al with comments I was planning to post regarding a

paper (authors Min and Tatar PMID: 16616772) he had posted earlier.

The authors claimed to have found a U-curve relationship between

casein consumption and longevity in fruit flies, which could be

interpreted to suggest we ought to restrict protein, or at least

casein. I had planned to post that I wasn't impressed by the paper

largely because most of the flies were given a diet that contained

zero fat. That hardly seemed to be the appropriate way to conduct an

experiment to ascertain information about the lifespans of flies in

response to variations in intake of protein in general and casein in

particular. Might not the total absence of fat, I thought, be a

major factor responsible for the results? Most likely by artifically

shortening their lives?

However, Al then suggested that if I didn't like that particular

paper I might want to take a look at a couple of others in similar

vein. (And, he tactfully suggested, they might, possibly, cause me

to modify my proposed post. They did!) This has led to other

related papers and now I am sitting here sort of numb with shock. It

looks like there may be some very important conclusions to be drawn

about protein intake from all this. But first a note about how the

authors of the key papers conducted their studies:

[Fruit flies have their advantages for scientists studying aging. It

takes only a couple of months to perform a lifespan experiment in

fruit flies. But, even though we have a fair amount of genetic

overlap with them, our common ancestor with fruit flies lived so long

ago - perhaps 500 million years - it is understandable some people

might be cautious about assuming that findings in fruit flies would

also be applicable to humans. Rats are more closely related to us,

but with them it takes about four years to do a lifespan experiment.

Plus perhaps a couple of additional years, taken up planning the

experiments and getting funding before they start and, after the

experiments are completed, writing up the paper and going through the

peer-review process. But there may be a good way to shorten the

timeframes, and complete an experiment in rats in just weeks: If

*biomarkers* of future longevity can be measured early, instead of

having to wait for all the rats to die, then perhaps reliable

conclusions can be drawn sooner, in a manner analogous, for example,

to that by which CVD risk is assessed early via lipids data.

In the case of biomarkers for lifespan it has been found that

mitochondrial production of reactive oxygen species (ROS) and damage

to mitochondrial DNA (mtDNA) is related to lifespan - the more of

them, or it, the shorter the lifespan. And also that CR both extends

lifespan and reduces mitochondrial DNA damage and ROS production So

perhaps it is reasonable to use these indicators as proxies for

lifespan long before all the subjects in the experiment are dead from

old age. This way it is possible to get a good idea after a

comparatively short period of time, seven weeks in this case, what

the experimental animals' lifespans will be, and therefore what the

long term effects will be of an experimental treatment. So the

authors of these papers experimented to determine the effects of

restricting the macronutrient content of the diets of rats, by

measuring ROS production and mtDNA damage and then, after just seven

weeks, drew conclusions about the likely lifespan effects. Waiting

seven weeks is, of course, much better than four years. But they

didn't actually measure lifespans.]

So, with the foregoing qualifications out of the way, here are the

papers of interest, along with the conclusions it seems should be

drawn from them. Of course if I have gotten this all wrong I know

someone will be kind enough to post a rebuttal, pointing out where,

what and how : ^ ))) And, of course, I welcome such a rebuttal if

it is required. I will caution that there is a fair amount of stuff

in these papers that is well beyond my biochemistry pay grade.

================================

To start with, we know that rats fed 40% fewer calories live 40%

longer. But the mechanism by which this happens is far from

understood.

About eighteen months ago the team at University College, London, UK

published a paper titled " Calories Do Not Explain Extension of Life

Span by Dietary Restriction in Drosophila " . By this they meant that

when flies, normally feeding on sugar and yeast, were sizeably

restricted only in sugar they lived only a little longer. This

implied, of course, that it was the restriction of the yeast that was

more important for lifespan extension. The yeast in their diet

supplies the fat and protein. The following is a reference to that

paper:

" Calories Do Not Explain Extension of Life Span by Dietary

Restriction in Drosophila. "

July 2005. PMID: 16000018. Public Library of Science. Volume 3,

Issue 7.

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In addition a paper was posted here about a survey of chinese

centenarians which found, among many other things, that on average

they were consuming only 40g of protein per day. This prompted

speculation as to whether this might possibly be a causal factor in

their remarkable longevity. Could restriction of protein be what is

important? This study was nowhere remotely close to being able to

attribute their longevity to the low protein intake. But it did seem

at least to reassure that such low protein intake is not dangerous,

otherwise they would not still have been alive. In addition, if

restricting protein to 40g was a factor enabling these people to live

to 100 years of age, one might wonder whether 30g might have been

even better. The paper was:

PMID: 11677774. Author: Chen C.

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The next paper of interest here is that authored by: Sanz A Caro P

Ibanez J Gomez J Gredilla R Barja G:

" Dietary restriction at old age lowers mitochondrial oxygen radical

production and leak at complex I and oxidative DNA damage in rat

brain. "

April 2005. PMID: 15906153. J Bioenerg Biomembr. 2005 Apr;37(2):83-

90.

This paper showed an association between dietary restriction on the

one hand and ROS and mtDNA damage on the other. ........... From

the abstract:

" Previous studies in mammalian models indicate that the rate of

mitochondrial reactive oxygen species ROS production and the ensuing

modification of mtDNA link oxidative stress to aging rate. However,

there is scarce information concerning this in relation to caloric

restriction (CR) in the brain, an organ of maximum relevance for

ageing. Furthermore, it has never been studied if CR started late in

life can improve those oxidative stress-related parameters. In this

investigation, rats were subjected during 1 year to 40% CR starting

at 24 months of age. This protocol of CR significantly decreased the

rate of mitochondrial H(2)O(2) production (by 24%) and oxidative

damage to mtDNA (by 23%) in the brain below the level of both old and

young ad libitum-fed animals. In agreement with the progressive

character of aging, the rate of H(2)O(2) production of brain

mitochondria stayed constant with age. Oxidative damage to nuclear

DNA increased with age and this increase was fully reversed by CR to

the level of the young controls. ...... The results agree with the

idea that CR decreases aging rate in part by lowering the rate of

free radical generation of mitochondria in the brain. "

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Also, in PMID: 17136610, Sanz Gomez Caro and Barja showed that

***carbohydrate*** restriction did not show these benefits. These

findings were very similar to those of the University College,

London, UK paper covering experiments in fruit flies, noted above.

From the abstract:

" Many previous investigations have consistently reported that caloric

restriction (40%), which increases maximum longevity, decreases

mitochondrial reactive species (ROS) generation and oxidative damage

to mitochondrial DNA (mtDNA) in laboratory rodents. These decreases

take place in rat liver after only seven weeks of caloric

restriction. ........... In the present study, using semipurified

diets, the carbohydrate ingestion of male Wistar rats was decreased

by 40% below controls without changing the level of intake of the

other dietary components. After seven weeks of treatment the liver

mitochondria of the carbohydrate restricted animals did not show

changes in the rate of mitochondrial ROS production, mitochondrial

oxygen consumption or percent free radical leak ............. . In

agreement with this, the levels of oxidative damage in hepatic mtDNA

and nuclear DNA were not modified in carbohydrate restricted

animals. ....... "

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In addition, in PMID: 16803986 Sanz, Caro, and Barja found

that ***fat*** restriction did not produce these benefits either.

From the abstract:

" ............. In the present study we have investigated the

possible role of dietary lipids in the effects of caloric restriction

on mitochondrial oxidative stress. Using semipurified diets, the

ingestion of lipids in male Wistar rats was decreased by 40% below

controls, while the other dietary components were ingested at exactly

the same level as in animals fed ad libitum. After 7 weeks of

treatment the liver mitochondria of lipid-restricted animals showed

significant increases in oxygen ................. Neither

mitochondrial H(2)O(2) production nor oxidative damage to

mitochondrial or nuclear DNA was modified in lipid-restricted

animals. ........... These results deny a role for lipids and

reinforce the possible role of dietary proteins as being responsible

for the decrease in mitochondrial ROS production and DNA damage in

caloric restriction. "

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In PMID: 15692733 Sanz, Caro and Barja showed that, a 40% restriction

of ***protein*** did dramatically improve these longevity biomarkers

and therefore, it is presumed, increase lifespan. From this abstract:

" Previous studies have shown that caloric restriction decreases

mitochondrial oxygen radical production and oxidative DNA damage in

rat organs, which can be linked to the slowing of aging rate induced

by this regime. In this study the possible role of the dietary

protein was investigated. Using semipurified diets, the ingestion of

proteins of Wistar rats was decreased by 40% below that of controls

while the other dietary components were ingested at the same level as

in animals fed ad libitum. After seven weeks in this regime the liver

of the protein restricted animals showed 30-40% decreases in

mitochondrial production of reactive oxygen species (ROS) and in

oxidative damage to nuclear and mitochondrial DNA. ........... These

results are strikingly similar to those previously obtained after 40%

caloric restriction in the liver of Wistar rats. Thus, the results

suggest that part of the decrease in aging rate induced by caloric

restriction can be due to the decreased intake of proteins acting

through decreases in mitochondrial ROS production and oxidative DNA

damage. ................ "

So, according to this, 40% protein restriction results in an

equivalent reduction in these key biomarkers of longevity. This

seems to indicate that protein restriction alone may account for

much, if not most, of the benefits of CR.

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But they went still further. In PMID: 16770005, the same authors,

along with others, found that restriction of just one amino acid

***methionine*** (Met) had effects very similar to those observed

with 40% protein restriction. From the abstract:

" Previous studies have consistently shown that caloric restriction

(CR) decreases mitochondrial reactive oxygen species (ROS) (mitROS)

generation and oxidative damage to mtDNA and mitochondrial proteins,

and increases maximum longevity, although the mechanisms responsible

for this are unknown. We recently found that protein restriction (PR)

also produces these changes independent of energy restriction.

Various facts link methionine to aging, and methionine restriction

(MetR) without energy restriction increases, like CR, maximum

longevity. We have thus hypothesized that MetR is responsible for the

decrease in mitROS generation and oxidative stress in PR and CR. In

this investigation we subjected male rats to exactly the same dietary

protocol of MetR that is known to increase their longevity. We have

found, for the first time, that MetR profoundly decreases mitROS

production, decreases oxidative damage to mtDNA, lowers membrane

unsaturation, and decreases all five markers of protein oxidation

measured in rat heart and liver

mitochondria. ................... These changes are strikingly

similar to those observed in CR and PR, suggesting that the decrease

in Met ingestion is responsible for the decrease in mitochondrial ROS

production and oxidative stress, and possibly part of the decrease in

aging rate, occurring during caloric restriction. "

And from the discussion section of the paper: " This strongly

suggests that the decrease in methionine intake is the cause of these

effects consistently found in many investigations on caloric

restriction in rodents. "

However, in this particular study Met was restricted by 94%. So if

94% restriction only results in reductions in these biomarkers

similar to those associated with 40% CR (with such a large degree of

restriction one might have expected more) then perhaps there are

other amino acids that also need to be restricted for maximum benefit

(cysteine, tryptophan and homocysteine may be prime suspects in this

respect). In addition, is there reason to suppose that 94% Met

restriction is optimal? Perhaps that is too severe? Met is, after

all, an essential nutrient. In any event, this study made no attempt

to determine the optimal degree of Met restriction.

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One additional paper, PMID: 8429371 dating from 1993, also found

extension of lifespan with Met restriction in rats. In this case 80%

restriction was found to extend lifespan by 30%. This may be the

information which encouraged Sanz, Caro, Barja et al to study Met to

see if it may be the amino acid explaining the apparent benefits of

protein restriction. The paper was PMID: 8429371:

' Low methionine ingestion by rats extends life span.'

Orentreich N, Matias JR, DeFelice A, Zimmerman JA.

" Dietary energy restriction has been a widely used means of

experimentally extending mammalian life span. We report here that

lifelong reduction in the concentration of a single dietary

component, the essential amino acid L-methionine, from 0·86 to 0·17%

of the diet results in a 30% longer life span of male Fischer 344

rats. .............. "

It certainly does not look like substantial Met restriction is

harmful in rats.

More to come .........................

Rodney.