The free radical theory of aging is backed by more than seven decades of research on calorie restriction. In 1935 Clive McCay, a professor of nutrition at Cornell, noted that if laboratory rats are fed only about two-thirds of the food they would freely choose to eat, their life spans increase by 40 percent to 50 percent. This result has been confirmed many times since then. Researchers think that semi-starvation may make metabolic processes more efficient, producing fewer free radicals and also perhaps boosting cells' DNA repair systems, since the hungry organism may have to live longer in order to reproduce.
Besides free radicals and telomere shortening, re-searchers have long noted that as our bodies age the levels of several key hormones begin to decline -- testosterone for men, estrogen in women, DHEA and growth hormone for everyone. Boosting the levels of these hormones has become the stock in trade for the growing business of longevity clinics.
Immortality When?
So what are your chances of living forever? First the bad news. As U.C.San Francisco's Leonard Hayflick recently told The Washington Post, "There is no intervention that has been proven to slow, stop, or reverse aging. Period."
Now the good news: Despite that, researchers are making a lot of progress.
Probably the most promising immediate thing you can do to increase your chances of seeing your great-grandchildren is to stop eating so much. Calorie restriction is the only known technique for increasing the life spans of many different organisms. The foremost advocate of this approach is probably the UCLA biologist Roy Walford, whose Web site offers menus for those who want to pursue longer life by dieting themselves nearly to death. Calorie restriction may not make your life longer, but it will certainly make it feel that way.
Barbara Hansen, a diabetes researcher at the University of Maryland, has spent 20 years investigating the effects of calorie restriction on rhesus monkeys. The experiment has not run long enough to determine if the ultimate life spans of the calorie-restricted monkeys will be increased. But on several related issues, her findings are unequivocal: When she compares old calorie-restricted monkeys to old monkeys that eat what they want, the calorie-restricted ones do not have heart disease, diabetes, or hypertension, and their cholesterol is lower. They're healthier.
There is no question that maintaining a reasonable weight prevents the onset of many illnesses associated with aging. But what if you find the notion of living without foie gras and pepperoni pizza unbearable? Is there hope for you?
There may be. Hansen hopes that by starving monkeys she can pave the way to a pill providing all the health benefits of calorie restriction while allowing you to inhale all the ice cream and beer you want. She has identified a compound that affects the PPAR-Delta receptor, which improves the body's response to insulin and glucose, mimicking the benefits of calorie restriction. It is now in early testing by Glaxo.
Calorie restriction research could also help us discover aging's elusive biomarkers. With the sequencing of the human genome and the advent of chip gene technologies, researchers can monitor the simultaneous actions of thousands of genes in tissues. The aim is to characterize the differences between the gene activity in tissues from old people and the gene activity in tissues from young people. Already, chip tests have found that the gene expression of tissues taken from old, calorie-restricted mice is similar to that found in young mice.
Among other benefits, finding such biomarkers would be a major advance in testing interventions for their effectiveness in slowing aging. Right now, the only way to see whether a proposed longevity treatment works is to wait for people to die.
Cloning for Longevity
If calorie restriction isn't your cup of tea, regenerative medicine is the next best bet for near-term success. The most promising path to regenerative medicine is the controversial process known as therapeutic cloning. If you need a new heart or liver, it might be possible to grow a new perfect transplant using your own cells. The process would involve transferring the nucleus of one of your skin cells to an enucleated human egg, which would then grow in a petri dish to the blastocyst stage. Stem cells would be harvested from the blastocyst and transformed into the desired tissues for transplant.
Stem cells have been found in adult tissues, in umbilical cord blood from newborns, and in embryos. All have shown some promise. William Haseltine, the CEO of Human Genome Sciences, recently predicted in The Washington Post that it will one day be possible to "reseed the body with our own cells that are made more potent and younger, so we can repopulate the body." But stem cell transplants are at least 10 years away -- or even longer, if Leon Kass and his allies succeed in banning therapeutic cloning. Since the chorus calling for a ban includes President Bush, the prospects for research in this area are not as bright as they ought to be.
Another problem: Regenerative medicine does not stop or slow aging. It just fixes the problems and diseases that accompany aging. In a sense, it's just a better form of conventional medicine. Continually trading in your old, worn-out organs for new ones is certainly better than the alternative, but it would be ever so much more pleasant if you could just stay young forever.
Editor's Note: We invite comments and request that they be civil and on-topic. We do not moderate or assume any responsibility for comments, which are owned by the readers who post them. Comments do not represent the views of Reason.com or Reason Foundation. We reserve the right to delete any comment for any reason at any time.
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