Thursday, July 9, 2009

Low-Calorie Diet May Extend Life in Primates

I am still a fan of calorie restriction, even though I am personally rather slack at it.

The New York Times has some exciting news for us CRONies:

Low-Calorie Diet May Extend Life in Primates

Published: July 9, 2009

A long-awaited study of aging in rhesus monkeys suggests, with some reservations, that people could in principle fend off the usual diseases of old age and considerably extend their life span by following a special diet.

Known as caloric restriction, the diet has all the normal healthy ingredients but contains 30 percent fewer calories than usual. Mice kept on such a diet from birth have long been known to live up to 40 percent longer than comparison mice fed normally.

Would the same be true in people? More than 20 years ago, two studies of rhesus monkeys were started to see if primates respond to caloric restriction the same way that rodents do. Since rhesus monkeys live an average of 27 years and a maximum of 40, these are experiments that require patience.

The results from one of the two studies, conducted by a team led by Ricki J. Colman and Richard Weindruch at the University of Wisconsin, were reported on Thursday in Science. The researchers say that now, 20 years after the experiment began, the monkeys are showing many beneficial signs of caloric resistance, including significantly less diabetes, cancer, and heart and brain disease. “These data demonstrate that caloric restriction slows aging in a primate species,” they conclude.

Some critics say this conclusion is premature. But in an interview, Dr. Weindruch called it “very good news.”

“It says much of the biology of caloric restriction is translatable into primates,” he said, “which makes it more likely it would apply to humans.”

In terms of deaths, 37 percent of the comparison monkeys have so far died in ways judged due to old age, compared with 13 percent of the dieting group, a difference that is statistically significant.

Dr. Weindruch and his statistician, David Allison of the University of Alabama, said the dieting monkeys are expected to enjoy a life span extension of 10 to 20 percent, based on equivalent studies started in mice at the same age.

Most normal people cannot in fact keep to a diet with 30 percent fewer calories than usual. So biologists have been looking for drugs that might mimic the effects of caloric restriction, conferring the gain without the pain. One of these drugs is resveratrol, a substance found in red wine, though in quantities too small to have any effect.

Dr. Weindruch said the study data offered “very encouraging” signs that resveratrol could duplicate in people some of the effects of caloric restriction.

Critics, however, are not yet ready to accept that the rhesus study proves caloric restriction works in primates.

If caloric restriction can delay aging, then there should have been significantly fewer deaths in the dieting group of monkeys than in the normally fed comparison group. But this is not the case. Though a fewer number of dieting monkeys have died, the difference is not statistically significant, the Wisconsin team reports.

The Wisconsin researchers say that some of the monkey deaths were not related to age and can properly be excluded. Some monkeys died under the anesthesia given while taking blood samples. Some died from gastric bloat, a disease that can strike at any age, others from endometriosis. When the deaths judged not due to aging are excluded, the dieting monkeys lived significantly longer.

Some biologists think it is reasonable to exclude these deaths, but others do not. Steven Austad, an expert on aging at the University of Texas Health Science Center, said that some deaths could be due to caloric restriction, even if they did not seem to be related to aging. “Ultimately the results seem pretty inconclusive at this point,” he said. “I don’t know why they didn’t wait longer to publish.”

Leonard Guarente, a biologist who studies aging at M.I.T., also had reservations about the findings. “The survival data needs to be fleshed out a little bit more before we can say that caloric restriction extends life in primates,” he said. In mouse studies, people just count the number of dead animals without asking which deaths might be unrelated to aging, he said.

The second rhesus monkey study, being conducted by the National Institute on Aging, is not as far advanced as the Wisconsin study. The researchers have not yet reported on the number of deaths in the dieting and normal monkey groups. But there are signs that the immune system is holding up better in the dieting group, said Julie Mattison, the leader of the N.I.H. study.

The outcome of the rhesus monkey studies bears strongly on the prospects of finding drugs that might postpone the aging process in people. Although people are unexpectedly similar to mice in many ways, they differ in other ways, notably cancer, a disease in which many treatments that are effective in mice do not work in people.

Even if caloric restriction extends longevity in people as well as mice, the extent of the effect remains unclear, though Dr. Weindruch believes the effects will be in the same general range. His monkeys were not started on the diet until 6 to 14 years of age, and seem to be doing as well as mice that are started at equivalent ages. The most striking extensions of life span occur only when the mice are put on the diet from birth.

Dietary restriction seems to trigger an ancient strategy written into all animal genomes, that when food is scarce resources should be switched from breeding to tissue maintenance. In recent years biologists have had considerable success in identifying the mechanisms by which cells detect the level of nutrients available to the body. The goal is to find drugs that trick these mechanisms into thinking that famine is at hand. People could then literally have their cake and eat it, enjoying the health benefits of caloric restriction without the pain of forgoing rich foods.
Read the whole thing.


Sungold said...

Oof. At this very moment I'm sucking down Ritz crackers topped with Brie, while daintily sipping Riesling. The wine is low-cal, I think. Or maybe I could petition to become a non-primate?

WV: obsess
Oh, yeah!

Wellescent Health Blog said...

While the results may have critics, which is a good thing, it shows that we are simply in the infancy of understanding the factors that contribute to aging in humans. I am sure this information will be analyzed from a large number of angles and will yield a lot of information given that it is the first study of higher level mammals.

K.C. Jones said...

As someone with a restrictive eating disorder, I must say I find articles like these to be offensive and take all the joy out of life. I'd rather enjoy my life than be 110.

sheila said...

Well, considering in ancient times people lived to hundreds of years old, I'd say something major happened somewhere. I don't think it's just disease and stuff that changed us.

I've heard about this whole red wine thing but I don't like the idea of it being a drug in pill form. I'm so sick of all the damn drugs. lol.

It would seem to me that if...IF...ancients lived as long as they did, it was something they ate or drank that contributed. no formulated drugs.

DaisyDeadhead said...

KC, if we could only keep the matter of "calories" and "weight" separate... the Calorie Restriction Society is continually reminding people that they are not a "diet" (as in weight loss) group. It really is a scientific experiment. Weight loss will probably happen as a result of the diet, but that is NOT their focus. (In fact, it is interesting how much the weight loss varies from person to person, as we've always known it does.)

I've learned a lot from them about densely-nutritional foods. But I can't get too awful gung-ho about it, since I'm just too prone to binging after, say, a week or two of restriction. I don't necessarily mind that, but it isn't something they have planned for in the experiment. I think they need to take the "psychology of plenty" into account...

And sorry to have offended you with this post!

I wish "calorie restriction" could be looked upon as "water restriction" or "gas restriction" or any other kind of attempt to restrict consumer intake of a basically-neutral substance...

K.C. Jones said...

I see that it's not about weight, but I still see it just as a way to restrict and control one's life and all that does is set one up for failure-as you've even noticed with yourself

Life cannot be controlled. I am quite familiar with a counting calories lifestyle and I know that it becomes/has the potential to become an obsession that I simply cannot support.

Meowser said...

Sandy at Junkfood Science just did a dissection of the NY Times piece and others on CR. One thing she pointed out, which got lost in much of the media hype, is that the CR monkeys were not eating 30 percent fewer calories than usual -- they were eating 30 percent less than the control group, which was being fed 20 percent more than usual. So the difference was more like 10 percent.

I'd be interested to know about your take on what she said. (Warning: piece is long.) It's here.

Also, where I keep getting stuck is that humans are exposed to a LOT more unfriendly bacteria than are lab animals. A lot of people over 70 are hit pretty hard by things like Staphylococcus infections, influenza, and pneumonia; in fact, those conditions can be absolutely deadly in senior populations. If CR weakens the immune system, wouldn't that make people more susceptible to getting killed by those things, especially with advancing age?

DaisyDeadhead said...

Meowser, fascinating! Linking this on the CR mailing list, and that should be interesting.

I can already tell you they will say the late Dr Walford's findings (from the Biosphere experiment) are not questionable or in doubt. And this "Junkfood Science" post appears to be focusing on the NYT piece and Dr Weindruch in particular, who obviously has some financial interest in marketing Resveratrol. Dr Walford, by contrast, was pretty pristine in comparison and had no financial incentive besides his books (which only sold moderately, since they were considered far too extreme to be successful 'diet books').

Speaking personally? I think the pattern humans are "meant" to have is one of caloric restriction (even severe), followed by a period of "plenty" or feasting. Then, repeat. This is also the pattern in most religions. I am thinking the pattern was first, then the religions adopted it or ritualized what was already widely practiced, rather than (as we often assume) the other way around.

I don't think extended caloric restriction is possible without obsession and neurosis, although some people seem to manage it very well. Most (on the CR list) appear to have very logical minds with little room for irrationality. The caloric restriction tends to allow for the irrationality, which suits them. However, some of us are already plenty irrational and don't need any MORE, thanks.

Still, I do think seasonal restriction is useful... I don't exactly know how we could do a study of that, though. humm...

Clicking over to the link Junkfood Science provided to the Resveratrol study, though, I got a bit put out with her: "just relax with a glass of red wine" indeed. Some of us can't do that, which is why we are interested in anti-oxidants like Resveratrol. I don't like her flip attitude, but then, that is also what I often dislike from the CR-people. Self-identified "science-minded" people are often very snooty and arrogant. They have it all figured out!

Not me though... I'm still collating. :)

Meowser said...

With Sandy, I take the good with the bad. I don't always agree with her politics (she's quite libertarian) or with some of the conclusions she draws. (To be fair, though she was quoting someone else about the "just relax with a glass of red wine" thing. I can't do that either unless I'm on stim holiday.) But nobody breaks down studies -- and especially, studies that have gotten a lot of media hype for the wrong reasons -- like she does.

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low-calorie-diets said...

Doesn't surprise me one bit. I think the evidence at this point is overwhelming that eating within a reasonable calorie limit keeps you healthy.