Can we stay young longer and postpone old age?
Yesterday was my birthday, and so I marked another milestone in my inevitable march to old age. Indeed, efforts to combat aging and extend life date as far back as 3500 BC and self-proclaimed experts have touted antiaging elixirs ever since. The prospect of immortality has always had universal appeal, spurring Ponce de Leon to search for the legendary fountain of youth. But the hawking of antiaging “therapies” has taken a particularly troubling turn of late. Disturbingly large numbers of entrepreneurs are luring gullible and frequently desperate people to “longevity” clinics, claiming a scientific basis for the antiaging products they recommend and, often, sell.
Alarmed by these trends, scientists who study aging have issued a position statement containing this warning: No currently marketed intervention — none — has yet been proved to slow, stop, or reverse human aging, and some can be downright dangerous. So anyone purporting to offer an antiaging product today is either mistaken or lying. Much of what is written in today’s article comes from that position statement, which was drafted and endorsed by 51 internationally recognized investigators.
What Aging Is And Isn’t
Aging is the accumulation of random damage to the building blocks of life — especially to DNA, certain proteins, carbohydrates and lipids (fats) — that begins early in life and eventually exceeds the body’s self-repair capabilities. This gradually impairs the functioning of cells, tissues, and organ systems, thereby increasing vulnerability to disease and giving rise to the characteristic manifestations of aging, such as loss of muscle and bone mass, action time, compromised hearing and vision, and reduced elasticity of the skin.
This accretion of molecular damage comes from many sources, including, ironically, the life-sustaining processes involved in converting the food we eat into usable energy. As the energy generators of cells (mitochondria) operate, they emit destructive, oxidizing molecules known as free radicals. Most of the damage caused by these reactive molecules gets repaired, but not all. Aging makes us even more susceptible to such ills as heart disease, Alzheimer’s disease, stroke and cancer, but these age-related conditions are superimposed on aging. Therefore, even if scientific advances could eliminate today’s leading killers of older individuals, aging would continue to occur. However, though inevitable, aging is not a genetically programmed process, playing itself out on a rigidly predetermined time schedule.
Men and women in the developed world typically live longer now (75 and 80 years, respectively) than they did throughout much of history (about 25 years) because human ingenuity — which brought us sanitation systems, vaccines, antibiotics, and so on — has had phenomenal success in thwarting the infections and parasitic diseases responsible for a great deal of premature death. We live longer now not because we have altered the way we age but because we have altered the way we live.
False Claims
There are researchers though, who believe, that they may manage to find ways to slow the rate of human aging. If they succeed, many people will live longer than would otherwise be expected, and a few people might even surpass the modern longevity record established by Jeanne Calment, a Frenchwoman who died in 1997 at the age of 122. (See photo taken during her 116th birthday party on Page E-1.) She survived longer than anyone whose age has been confirmed. But the primary goal of biomedical research and efforts to slow aging should not be the mere extension of life. Slowing the rate of aging could help postpone the onset of old age-related diseases and infirmities, essentially enabling people to stay younger longer. People eager to retain or restore their youthful biology might well recognize the paucity of proof but may decide to try antiaging intervention anyway, thinking that have nothing to lose. They should think again. For instance, products that are sold as dietary supplements do not undergo the rigorous tests of safety and effectiveness that drugs must pass before they can be sold to the public. Consequently, these supplements come with no guarantees of purity or potency, no established guidelines on dosage, and often no warning of side effects that may result when products are taken along with approved medications.
Antioxidants constitute one popular class of supplements touted to have antiaging powers. Such chemicals occur naturally in the body and in fruits and vegetables, and are believed to neutralize free radicals. Proponents claim that if taken in sufficient quantities, antioxidant supplements will sop up the radicals and slow down or stop the processes responsible for aging. But eliminating all free radicals would kill us, because they perform certain necessary intermediary steps in biochemical reactions. Further, although epidemiological studies have demonstrated that the antioxidant vitamins E and C contained within the foods we eat may reduce the risk of cancer, macular degeneration, and other disorders, no one has established that vitamin supplements containing antioxidants limit oxidative damage in the body or influence aging.
Like antioxidants, another fashionable antiaging intervention, hormone replacement, has a plausible rationale. This strategy was first popularized early in the 20th century, when older men occasionally submitted to the grafting of testicles from goats or monkeys or received injections of macerated testicles. The replacement strategy seems logical in principle because the blood levels of most hormones — among them melatonin, growth hormone, testosterone and dehydroepiandrosterone (DHEA) — commonly decrease with age. Also, experiments on older men have demonstrated that some physical and physiological attributes that show declines over time, notably muscle mass and skin elasticity, respond favorably in the short term to growth hormone replacement.
On the other hand, hormones can cause worrisome side effects. In mice, for instance, giving melatonin increases the risks of tumor development, and the overproduction of growth hormone leads to kidney problems, premature heart and lung failure, and an increased probability of early death. Human adults given growth hormone have suffered from acromegaly (excess bone growth) and carpal tunnel syndrome. Estrogen replacement therapy may offer health benefits to some postmenopausal women. In short, hormone replacement has a place in the treatment of specific age-associated disorders, but evidence that it affects the rate of aging is lacking.
Some people might wonder whether following today’s public health recommendations for diet and exercise can serve as a more natural Fountain of Youth. Good nutrition and regular exercise do reduce the risk of various diseases and, in that way, may extend the duration of life for many people — thereby serving as the best current prescription for a long and healthy life. As is true of other interventions, though, no one has shown that diet or exercise, or both, directly influences aging.
What Science Says
Serious efforts to understand aging have advanced greatly in recent years. Biologists who work with yeasts, roundworms, fruit flies, and mice have extended life by manipulating the genes of these species. Indeed, further study of those genes could offer clues to their influence on longevity and to approaches that might postpone infirmity and age-related disorders. Another avenue of research may also lead to true aging interventions. Investigators have known for decades that caloric restriction extends life and the duration of good health in all species in which it has been studied, as long as the diet includes enough nutrition for routine maintenance of the body. These findings suggest that caloric restriction might have similar effects on humans. Given that few people would ever reduce their food intake enough to lengthen their lives, biologists are now trying to discover the mechanisms that underlie the benefits of caloric restriction and to find agents that might mimic those helpful effects in people without forcing them to go hungry.
There are scientists who look at current research trends and feel hopeful. They envision a time when treatments based on an understanding of aging can slow its progression, and when stem cells can be coaxed to repair damaged tissues, enabling people to remain vigorous longer than they would without medical assistance. Not all researchers share that optimism though. Some assert that aging’s complexity will forever militate against the development of antiaging therapies. But one thing is indisputable: The number of older people is growing worldwide, and opportunists stand ready to cash in on the burgeoning market for antiaging products. The public needs to know that the product sold as antiaging remedies have no scientifically proved efficacy and, at times, can be harmful. Systematic investigations into aging and its modification are in progress and could one day provide methods to slow our inevitable decline and extend health and longevity. That day, however, has not dawned yet.
