9 replies to this topic

[scottl]

I know....almost nothing about CR but wonder if this stirs up some interesting discussion. (Thanks Pete--article courtesy of the relentless improvement blog)

http://www.relentles...t.blogspot.com/

Calorie restriction not the only way to increase longevity
Medical Research News
Published: Friday, 3-Jun-2005


New research carried out by University College London (UCL) scientists has found that it is possible to increase life expectancy by 50% without decreasing calorie intake - at least in fruitflies.
The research adds new complexity to the established view that dietary restriction works to extend life span by reducing calorie intake. This report reveals that the nutritional source (ie fat, protein, carbohydrate) of the calories is more important to longevity than a reduction in the total calories consumed.

The study published on 30th May 2005 in PLoS Biology, shows that fruitflies - 'Drosophila'- can live longer without reducing calories but instead by consuming proportionally less yeast (which is the flies' only source of protein and fat). The team, led by Professor Linda Partridge of UCL's Centre for Research on Ageing, Department of Biology, believes that this demonstrates that calorie intake is not the key factor in the reduction of mortality rate by dietary restriction in this species.

The authors restricted the diet of the fruitflies by diluting the nutrients in the fly's standard lab diet of yeast and sugar to a level known to maximize life span. Since both yeast and sugar (carbohydrates) provide the same calories per gram, the authors could adjust nutrient composition of the yeast/sugar mixture without affecting the calorie count, allowing them to separate the effects of calories and nutrients.

Reducing both nutrients increased the flies' life spans, but yeast had a much greater effect: reducing yeast in the mixture from 150 grams to 65 grams increased median life span by over 60%, compared to just 9% when calorie intake was reduced to the same extent by lowering sugar levels. Late-starters on the restricted-yeast diet gained the same benefits as the rest of the yeast-deprived group. Forty-eight hours after being switched from normal diets to yeast-restricted diets, flies were no more likely to die than flies fed the yeast-restricted diet throughout their adult life.

Professor Linda Partridge said: "Altogether these results make a strong case that calories per se are not the salient factor in prolonging life-at least in fruitflies. The dramatic impact of reducing yeast suggests that protein or fat plays a greater role in fly longevity than sugar. This suggests that yeast and sugar trigger different metabolic pathways with different effects on life span. The caloric-restriction/longevity paradigm is not as simple as current scientific thought believes and needs more rigorous review."


http://www.ucl.ac.uk/

[Mind]

This is kind-of a strange result. I humans, sugar is well known to have detrimental effects on longevity, and most nutritionists I know would err on the side of protein rather than sugar.

[johnmk]

I'd rather see primate studies than fruit fly studies here. Honestly I do not think we can apply this result to homosapiens.

[jaydfox]

I'd rather see primate studies than fruit fly studies here. Honestly I do not think we can apply this result to homosapiens.

Well, mammal studies to say the least. Primate studies take so long, and are so expensive, that we can't afford to chase every interesting result in flies, worms, and yeast. If it can't be validated in at least two different genera of mammals (e.g. mice and rabbits), then there's no point shelling out millions of dollars for primate studies that might show no effect. While showing no effect increases our knowledge (validates the null hypothesis), it's not worth the cost to chase every opportunity.

So I'd like to see concurrent studies in two different mammal genera (concurrent to reduce the time before we get all the results). Alas, I don't have the money to fund such experiments, so I'll settle for sending out creativity vibes, and hope some mammal labs out there pick up on this and decide to do followup studies.

[dnamechanic]

I pretty much must agree with you, johnmk.

The particular Drosophila paper that scottl is referring to, referenced a paper published in FASEB Journal.

"Effect of caloric restriction on life span of the housefly, Musca domestica."

http://www.ncbi.nlm....9362&query_hl=5

PMID: 15319362

In this study, it was shown that that calorie restiction (CR) failed to extend the lifespan of the housefly, Musca domestica.

CR shortened the housefly lifespan proportionately to the percentage restriction, i.e. 10% restriction shortened lifespan a small amount, 20% shortened more, and so on; 30%, 40% until starvation at 50% restriction.

The results of the housefly study raises some serious issues with the many claims made regarding calorie restriction in Drosophila.

This criticism may extend to all species smaller than a housefly, because food intake has not been directly measured in smaller species.

In the Housefly study, it was clearly shown that feeding sucrose-only substantially extended lifespan.

Feeding additional proteins or lipids shortened lifespan, but allowed fertility in females. Male houseflies remained fertile on a sucrose-only diet.

Can post the survival curves here if I can figure out how to post a .jpg file.

The pdf will be made available to anyone interested.

[scottl]

Yeesh. I'll stick to higher forms of life in the future.

[opales]

Äctually, I think that the positive effects of low-ptotein diets have been demonstrated also in rodents. however, these experiments have only been successful in sterilized envinronments. that is, in sterilized environments rodents on low-protein diet (with normal calorie consumption) have experienced the same life-extending benefits as experined in calorie restricted studies. however, due to detrimental effect of low protein diet to immune function, these effects are evened out in normal laboratory conditions due to increased susceptibility to viral/bacterial infections.

so basically, even though in theory low-protein diet would produce the same results as low-calorie diet, in practise the fact that low-protein weakens immune function makes it no better (actually, maybe worse) than the ordinary diet.

and of course, I cannot provide you with references, you're gonna have to do your own searches:)

[Set]

I refuse to believe the results will help humans at all, until it's tried on a "mammal".
Flies aren’t going to represent anything even close to the reactions of animals.
That’s why we use mice.
I think people just don’t want to go Cron.

[sub7]

How would testosterone levels effect lifespan in humans? Protein intake certainly has an impact on T levels?

[scottl]

How would testosterone levels effect lifespan in humans? Protein intake certainly has an impact on T levels?

Well...if you go to LEF.org you'll probably find info that test levels affect risk of heart disease.