Cron Diet Research Paper

A 2009 image of rhesus monkeys in a landmark study of the benefits of caloric restriction. The 27-year-old monkey on the left was given a diet with fewer calories while the 29-year-old monkey on the right was allowed to eat as much as it liked. Both animals have since died of natural causes. Photo: Jeff Miller

Settling a persistent scientific controversy, a long-awaited report shows that restricting calories does indeed help rhesus monkeys live longer, healthier lives.

A remarkable collaboration between two competing research teams — one from the University of Wisconsin–Madison and one from the National Institute on Aging — is the first time the groups worked together to resolve one of the most controversial stories in aging research.

The findings by the collaboration — including Senior Scientist Ricki Colman of the Wisconsin National Primate Research Center and UW–Madison Associate Professor of Medicine Rozalyn Anderson; and NIA Staff Scientist and Nonhuman Primate Core Facility Head Julie Mattison and Senior Investigator and Chief of the Translational Gerontology Branch Rafael de Cabo — were published today (Jan. 17, 2017) in the journal Nature Communications.

In 2009, the UW–Madison study team reported significant benefits in survival and reductions in cancer, cardiovascular disease, and insulin resistance for monkeys that ate less than their peers. In 2012, however, the NIA study team reported no significant improvement in survival, but did find a trend toward improved health.

“These conflicting outcomes had cast a shadow of doubt on the translatability of the caloric-restriction paradigm as a means to understand aging and what creates age-related disease vulnerability,” says Anderson, one of the report’s corresponding authors. Working together, the competing laboratories analyzed data gathered over many years and including data from almost 200 monkeys from both studies. Now, scientists think they know why the studies showed different results.

The upshot of the report is that caloric restriction does indeed seem to be a means to affect aging. However, for primates, age, diet and sex must all be factored in to realize the full benefits of lower caloric intake.

First, the animals in the two studies had their diets restricted at different ages. Comparative analysis reveals that eating less is beneficial in adult and older primates but is not beneficial for younger animals. This is a major departure from prior studies in rodents, where starting at an earlier age is better in achieving the benefits of a low-calorie diet.

Second, in the old-onset group of monkeys at NIA, the control monkeys ate less than the Wisconsin control group. This lower food intake was associated with improved survival compared to the Wisconsin controls. The previously reported lack of difference in survival between control and restricted groups for older-onset monkeys within NIA emerges as beneficial differences when compared to the UW–Madison data. In this way, it seems that small differences in food intake in primates could meaningfully affect aging and health.

Third, diet composition was substantially different between studies. The NIA monkeys ate naturally sourced foods and the UW–Madison monkeys, part of the colony at the Wisconsin National Primate Research Center, ate processed food with higher sugar content. The UW–Madison control animals were fatter than the control monkeys at NIA, indicating that at nonrestricted levels of food intake, what is eaten can make a big difference for fat mass and body composition.

Finally, the team identified key sex differences in the relationship between diet, adiposity (fat), and insulin sensitivity, where females seem to be less vulnerable to adverse effects of adiposity than males. This new insight appears to be particularly important in primates and likely is translatable to humans.

The upshot of the report is that caloric restriction does indeed seem to be a means to affect aging. However, for primates, age, diet and sex must all be factored in to realize the full benefits of lower caloric intake.

Share via Facebook

Share via Twitter

Share via Linked In

Share via Email

* New study shows extreme calorie restriction does not extend lifespan

* Surprising disconnect between health and longevity

* A diet "that makes us live longer may not exist" - expert

By Sharon Begley

NEW YORK, Aug 29 (Reuters) - The longevity diet's premise is seductively simple: cutting your calorie intake well below your usual diet will add years to your life.

New research published on Wednesday, however, shows the extreme, emaciating diet doesn't increase lifespan in rhesus monkeys, the closest human relatives to try it in a rigorous, long-running study. While caveats remain, outside experts regarded the findings as definitive, particularly when combined with those from a similar study.

"If there's a way to manipulate the human diet to let us live longer, we haven't figured it out yet and it may not exist," said biologist Steven Austad of the University of Texas Health Science Center's Barshop Institute for Longevity and Aging Studies, who wrote an analysis of the study in Nature.

Since 1934, research has shown that lab rats, mice, yeast, fruit flies and round worms fed 10 percent to 40 percent fewer calories than their free-eating peers lived some 30 percent longer. In some studies, they lived twice as long.

Such findings have spawned a growing community of believers who seek better health and longer life in calorie-restricted (CR)diets, as promised in the 2005 book "The Longevity Diet," including 5,000 members of the CR Society International. The research has also prompted companies like Procter & Gamble and Nu Skin Enterprises to develop drugs to mimic the effects of calorie restriction.

The new study, from the National Institute on Aging, part of the U.S. National Institutes of Health, suggests a surprising disconnect between health and lifespan. It found that most of the 57 calorie-restricted monkeys had healthier hearts and immune systems and lower rates of diabetes, cancer or other ills than the 64 control monkeys. But there was no longevity pay-off.

"You can argue that the calorie-restricted animals are healthier," said Austad. "They have better cholesterol profiles, less muscle loss, less disease. But it didn't translate into greater longevity. What we learn from this is you can un-link health and longevity."

YOUNGER IMMUNE SYSTEMS, LESS HEART DISEASE

The NIA study, launched in 1987, is one of two investigating whether eating just 70 percent of the calories in a standard lab diet extends life in a long-lived primate. The Wisconsin National Primate Research Center's study, begun in 1989, also uses rhesus monkeys, whose physiology, genetics and median lifespan (27 years) are closer to humans than are the rodents in earlier calorie-restriction research.

Initial results were promising. In 2006 the NIA group reported that calorie-restricted monkeys had younger-seeming immune systems. Wisconsin reported that after 20 years of eating like birds, the monkeys were less likely to get heart disease, diabetes, cancer and other diseases of aging.

They also lived longer: By 2009, 80 percent of the free-eating Wisconsin monkeys had died of age-related illness, but only 50 percent of calorie-restricted monkeys had. Those findings, the scientists reported at the time, showed "that CR slows aging in a primate species."

Experts on aging have since waited for the NIA to weigh in, and the verdict was a shock: "The calorie-restricted monkeys lived no longer than the other monkeys," NIA's Julie Mattison, who helped lead the study, told Reuters.

The oldest animals in each group had the same incidence of tumors, heart disease and general deterioration. While the abstemious monkeys had some improved health markers such as cholesterol and triglyceride levels, Mattison said, "that didn't translate into better survival."

The NIA study showed that even monkeys starting calorie restriction early in life, from 1 to 14 years of age, had no lifespan edge over their gourmand peers. With 19 of the 40 monkeys whose eating was restricted starting in youth still alive, the NIA scientists calculated, the chance that they will outlive free-eating monkeys is less than one-tenth of 1 percent.

Perhaps more surprising, health markers were often worse in monkeys that began calorie restriction as young adults than older ones, the opposite of what scientists expected. And more of the animals that started calorie restriction when young died of causes unrelated to aging than did their free-eating peers. "There may be something about calorie restriction that makes animals more susceptible to death from other causes," said Austad.

A KILLER CONTROL GROUP

Scientists offered several explanations for why the NIA's findings differ from more encouraging results in the Wisconsin study.

The Wisconsin monkeys' diet had seven times the table sugar (28 percent of calories, like Americans' diets) as the NIA's (4 percent). The Wisconsin control monkeys also ate however much they wished; the NIA control monkeys ate a fixed amount and, as a result, weighed less.

That suggests the longevity diet didn't really extend lifespan in the Wisconsin monkeys: It only seemed to because the control monkeys ate themselves into an early grave.

"Comparing calorie restriction to what you think is a normal diet but is in fact an unhealthy diet with too much food and too much sucrose can trip you up," said Austad. "If you keep your control animals to a healthy weight, as the NIA did, a diet that produces extreme emaciation has no further effect on longevity."

Most problematic, many of the Wisconsin study's calorie-restricted monkeys died of causes unrelated to aging, such as anesthesia used in some experiments and gastrointestinal bloat.

Only by not counting those deaths did the Wisconsin scientists find a statistically significant longevity effect, said Wisconsin's Ricki Colman, a leader of that study.

It is too soon to know how the NIA study will affect the development of drugs aimed at replicating calorie restriction's benefits without the hunger pangs. They include mannoheptulose, a compound derived from unripe avocados that "tricks cells into thinking they ate less," said George Roth, CEO of privately held GeroScience.

Roth helped launch the NIA study and is a co-author of the new paper. He believes there is still good evidence in favor of calorie restriction, including the Wisconsin study's findings. GeroScience is working with Procter & Gamble to use mannoheptulose as a lifespan-increasing supplement for dogs and hopes to raise money for a clinical trial in people.

LifeGen Technologies, co-founded by a leader of the Wisconsin study, has tested a compound that mimicked some genetic changes seen with calorie restriction in rodents. In 2001, the company was bought by Nu Skin, which "utilizes the research data generated from caloric restriction studies to assist in its development of nutritional supplements," a spokeswoman said.

The NIA and Wisconsin teams are continuing to collect data to see if calorie restriction suddenly proves more beneficial. "But what I take away from these studies is that extreme emaciation may not be the correct paradigm," said University of Texas biologist Austad. "If I were them (companies or scientists banking on this), I'd be worried."

0 comments

Leave a Reply

Your email address will not be published. Required fields are marked *