When we think about aging, we often consider the aesthetic implications of the inevitable march of time, such as graying hair or wrinkled skin. But the real aging process happens on a level unseen to the naked eye. It is also a process that affects all organisms, not just humans.
Age-related damage happens at the cellular level as a result of biological processes within a cell, and the cause and extent of the damage depends on a myriad of factors, such as genes, environment and diet.
By examining just one of those potential antagonists (no easy task from an experimental design standpoint) scientists can explore the extent to which that one source of damage is responsible for the aging process, and a new study published in the journal Science Advances does just that.
For their study, an international team of researchers looked at how molecular changes in diet affected the lifespans of three different kinds of organisms: yeast, fruit flies and mice. In each group, the organisms were divided according to the age of the food they were fed, so some organisms had a diet of "young" food, meaning nutritional input from relatively short-lived organisms, while others were fed "old" food, or a diet composed of nutrition from relatively long-lived organisms.
In the case of mice, for example, the diet of "young" food meant the skeletal muscle of 3-year-old deer, while those in the "old" food group consumed the equivalent tissue from 25-year-old deer.
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What the researchers found is that organisms fed a diet of old food had shorter lifespans - on the order of about 10 percent shorter in fact - than their counterparts who consistently ate "young" food. The results suggest that diet is only one contributor of the aging process, and other factors such as genes account for further variance in longevity.
There are a few caveats to the findings, however. In the case of mice, for example, the researchers only observed the negative effects of old food in the longevity of female mice, a result that is partly due to the limited number of mice involved in the experiment as well as time and diet limitations.
"What is encouraging is we could see this effect in all three cases, and it's all in the same direction, which suggests to us it's real," Vadim Gladyshev, professor of medicine at Harvard Medical School and director of redox medicine at Brigham and Women's Hospital, told Seeker. "But at the same time, the design of the experiment is such that it's impossible to make a perfect control for it."
Although the research did produce consistent findings across all three species, that doesn't mean people should start thinking about adjusting their intake based just on this study's findings.
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"I cannot possibly recommend anything for humans," Gladyshev noted. So to be clear, based on the study, no one should start throwing out old food. The sorts of diets used in the experiment were strict by design, and in a way that no human would or should ever follow. The effect is also not that large relative to other potential aging factors.
That doesn't mean, however, that people don't benefit from this sort of research. The study looked into a fundamental antagonist that affects the aging process, and confirmed the effects of one particular form of damage, specifically age-related molecules introduced through diet. "And so, the damage in this case, it's like a marker of the aging process," Gladyshev said. "And so, how can we delay this process? How can we target the damage?"
Exploring these fundamental issues can certainly advance biomedical research, which is often focused on a particular disease rather than aging itself. Even if researchers were able to eradicate a condition like Alzheimer's, for example, older individuals would still confront the other health conditions in their advancing years, Gladyshev said. "But if we are able to target the aging process itself, we could delay the incidents of all of the age-related diseases at once."
While the Science Advances paper can't make any recommendations as far as human diets go, a separate study published earlier this week in the journal Science Translational Medicine finds that it's possible to reduce the risk of aging and major diseases, such as diabetes, cancer and cardiovascular disease, through the use of a fasting-mimicking diet, or FMD.
"People have been looking at something called calorie restriction for 100 years, but calorie restriction has never moved to mainstream because it causes both solutions and problems," Valter D. Longo, professor of gerontology and Biological Sciences at the University of Southern California, told Seeker.
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Past research has offered mixed results in terms of the potential health benefits of a calorie-restricted diet. "The fasting-mimicking diet is an attempt to keep the good parts of the calorie-restricted diet and eliminating the bad," Longo added.
For the study, a total of 71 adults out of a 100-person randomized trial completed five-day cycles of a FMD - a diet of between 750 and 1,100 calories with precise proportions of macronutrients (protein, carbohydrates and fats) - once a month over a period of three months. What the researchers found in the participants who completed the diet was consistent with an anti-aging, pro-longevity effect.
Specifically, those that completed the diet lost an average of six pounds. The participants also lost body fat, but not muscle, and their waistlines shrank by 1 to 2 inches. Level of blood pressure, blood sugar, cholesterol and IGF-1, a hormone linked to metabolism, all moved toward healthier levels. Not only that, but three months after the conclusion of the last cycle, the researchers found that many of the health benefits remained.
"The key is not so much the weight loss, but the combination of the weight loss and the rebuilding/regeneration component," Longo noted.
During a fast, various systems in the body lose cells and cells also lose parts of their structure. When a normal diet is restored, that's where the rebuilding process comes in.
Despite the benefits, this type of diet isn't necessarily for everyone. Longo cautions that anyone over 70 years old or not in good health should consult a doctor before considering such an approach, and even healthy adults should at least consult a registered dietitian before adopting such a program.
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