Comments re CR

[Guest guest]

Hi All,

The below may be of interest. Although it discusses a previously presented

study,

the comments by CR researchers are revealing.

' " I look forward to reporting the outcome, " [Weindruch] says, " assuming the

monkeys

don't outlive me! " '

Nature 435, 548 (2 June 2005) | doi: 10.1038/nature03861

Yeast feeds debate on prolonging life

Carina Dennis

'Eating less helps you live longer' has for decades been the message from

researchers of ageing. So experts are not sure what to make of a study in flies

that

suggests it could be what you eat, not how much you eat, that really counts.

The idea that restricting calories prolongs lifespan was first reported in 1935,

following studies in rats. The observation has since been supported by studies

in

species ranging from worms to dogs. The source of the calories is generally

considered irrelevant.

Now a research team from University College London has extended the lifespan of

Drosophila flies by reducing the amount of yeast (a source of protein and fat)

or

sugar in their diets. The team, led by Partridge, observed a much more

dramatic effect with yeast than with sugar, even though the overall change in

calorie content was the same. The results are published online in PLoS Biology

this

week (W. Mair et al. 3, 223; 2005).

The finding hints that reducing protein and fat might be the key to living

longer,

rather than cutting down on the total number of calories. But many researchers

are

sceptical of drawing any broad conclusions. " We already saw what a disaster it

was

in the 1990s with fad diets that lowered fats and increased carbs, " says Leonard

Guarente, a molecular biologist at the Massachusetts Institute of Technology in

Cambridge. " That's when people really got fat. "

He thinks the results may simply reflect a peculiarity of flies. " You need to

know

how well flies metabolize glucose compared with yeast, " he says.

Sige Zou, a fly geneticist at the National Institute on Aging in Baltimore, adds

that other components in the yeast might also be having an effect. " Yeast are

made

up of a lot of ingredients, " he says. He would like to see the experiment

repeated

using pure protein or fat extracts.

Partridge's study shows how tricky it can be to pin down such effects, agrees

Weindruch, a gerontologist at the University of Wisconsin at Madison.

" This

solidifies my concerns about the nuances and difficulties of conducting studies

of

caloric restriction in some model organisms. "

But researchers are sure, at least, that restricting calories does prolong

lifespan,

even if they do not know how. " The name of the game is not to take in more

energy

than you need, " says Guarente.

How many calories would humans need to cut to gain years, or even decades?

" Based on

our mouse data, I'd guess a minimum of 20% from a predetermined baseline, for a

person who is not obese, " says Weindruch.

Weindruch is currently evaluating diet-restricted rhesus monkeys, in a study

that

started more than a decade ago. " The monkeys are now middle-aged and it is clear

the

diet is doing them good, " says Weindruch. They are protected from type II

diabetes,

a common ailment in ageing monkeys, and seem to have healthier hearts. " I look

forward to reporting the outcome, " he says, " assuming the monkeys don't outlive

me! "

Al Pater, PhD; email: old542000@...

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