Strategies and issues regarding life extension
Diets and supplements
Much life extension research focuses on nutrition—diets or supplements—as a means to extend lifespan, although few of these have been systematically tested for significant longevity effects. The many diets promoted by anti-aging advocates are often contradictory. A dietary pattern with some support from scientific research is caloric restriction.
Preliminary studies of caloric restriction on humans using surrogate measurements have provided evidence that caloric restriction may have powerful protective effect against secondary aging in humans. Caloric restriction in humans may reduce the risk of developing Type 2 diabetes and atherosclerosis.
The free-radical theory of aging suggests that antioxidant supplements, such as vitamin C, vitamin E, Q10, lipoic acid, carnosine, and N-acetylcysteine, might extend human life. However, combined evidence from several clinical trials suggest that β-carotene supplements and high doses of vitamin E increase mortality rates. Resveratrol is a sirtuin stimulant that has been shown to extend life in animal models, but the effect of resveratrol on lifespan in humans is unclear as of 2011.
There are many traditional herbs purportedly used to extend the health-span, including a Chinese tea called Jiaogulan (Gynostemma pentaphyllum), dubbed “China’s Immortality Herb.” Ayurveda, the traditional Indian system of medicine, describes a class of longevity herbs called rasayanas, including Bacopa monnieri, Ocimum sanctum, Curcuma longa, Centella asiatica, Phyllanthus emblica, Withania somnifera and many others.
The anti-aging industry offers several hormone therapies. Some of these have been criticized for possible dangers to the patient and a lack of proven effect. For example, the American Medical Association has been critical of some anti-aging hormone therapies.
Although some recent clinical studies have shown that low-dose growth hormone (GH) treatment for adults with GH deficiency changes the body composition by increasing muscle mass, decreasing fat mass, increasing bone density and muscle strength, improves cardiovascular parameters (i.e. decrease of LDL cholesterol), and affects the quality of life without significant side effects, the evidence for use of growth hormone as an anti-aging therapy is mixed and based on animal studies. There are mixed reports that GH or IGF-1 signaling modulates the aging process in humans and about whether the direction of its effect is positive or negative.
Scientific controversy regarding anti-aging nutritional supplementation and medicine
Some critics dispute the portrayal of aging as a disease. For example, Leonard Hayflick, who determined that fibroblasts are limited to around 50 cell divisions, reasons that aging is an unavoidable consequence of entropy. Hayflick and fellow biogerontologists Jay Olshansky and Bruce Carnes have strongly criticized the anti-aging industry in response to what they see as unscrupulous profiteering from the sale of unproven anti-agingsupplements.
Consumer motivations for using anti-aging products
Research by Sobh and Martin (2011) suggests that people buy anti-aging products to obtain a hoped-for self (e.g., keeping a youthful skin) or to avoid a feared-self (e.g., looking old). The research shows that when consumers pursue a hoped-for self, it is expectations of success that most strongly drive their motivation to use the product. The research also shows why doing badly when trying to avoid a feared self is more motivating than doing well. Interestingly, when product use is seen to fail it is more motivating than success when consumers seek to avoid a feared-self.
The best-characterized anti-aging therapy was, and still is, CR. In some studies calorie restriction has been shown to extend the life of mice, yeast, and rhesus monkeys significantly. However, a more recent study has shown that in contrast, calorie restriction has not improved the survival rate in rhesus monkeys. Long-term human trials of CR are now being done. It is the hope of the anti-aging researchers that resveratrol, found in grapes, or pterostilbene, a more bio-available substance, found in blueberries, as well as rapamycin, a biotic substance discovered on Easter Island, may act as CR mimetics to increase the life span of humans.
More recent work reveals that the effects long attributed to caloric restriction may be obtained by restriction of protein alone, and specifically of just the sulfur-containing amino acids cysteine and methionine. Current research is into the metabolic pathways affected by variation in availability of products of these amino acids.
There are a number of chemicals intended to slow the aging process currently being studied in animal models. One type of research is related to the observed effects a calorie restriction (CR) diet, which has been shown to extend lifespan in some animals Based on that research, there have been attempts to develop drugs that will have the same effect on the aging process as a caloric restriction diet, which are known as Caloric restriction mimetic drugs. Some drugs that are already approved for other uses have been studied for possible longevity effects on laboratory animals because of a possible CR-mimic effect; they include rapamycin, metformin and other geroprotectors. Resveratrol and pterostilbene are dietary supplements that have also been studied in this context.
Other attempts to create anti-aging drugs have taken different research paths. One notable direction of research has been research into the possibility of using the enzyme telomerase in order to counter the process oftelomere shortening. However, there are potential dangers in this, since some research has also linked telomerase to cancer and to tumor growth and formation. In addition, some preparations, called senolytics are designed to effectively deplete senescent cells, that poisoning an organism by their secretions.
Future advances in nanomedicine could give rise to life extension through the repair of many processes thought to be responsible for aging. K. Eric Drexler, one of the founders of nanotechnology, postulated cell repair machines, including ones operating within cells and utilizing as yet hypothetical molecular computers, in his 1986 book Engines of Creation. Raymond Kurzweil, a futurist and transhumanist, stated in his book The Singularity Is Near that he believes that advanced medical nanorobotics could completely remedy the effects of aging by 2030.
Cloning and body part replacement
Some life extensionists suggest that therapeutic cloning and stem cell research could one day provide a way to generate cells, body parts, or even entire bodies (generally referred to as reproductive cloning) that would be genetically identical to a prospective patient. Recently, the US Department of Defense initiated a program to research the possibility of growing human body parts on mice. Complex biological structures, such as mammalian joints and limbs, have not yet been replicated. Dog and primate brain transplantation experiments were conducted in the mid-20th century but failed due to rejection and the inability to restore nerve connections. As of 2006, the implantation of bio-engineered bladders grown from patients’ own cells has proven to be a viable treatment for bladder disease. Proponents of body part replacement and cloning contend that the required biotechnologies are likely to appear earlier than other life-extension technologies.
The use of human stem cells, particularly embryonic stem cells, is controversial. Opponents’ objections generally are based on interpretations of religious teachings or ethical considerations. Proponents of stem cell research point out that cells are routinely formed and destroyed in a variety of contexts. Use of stem cells taken from the umbilical cord or parts of the adult body may not provoke controversy.
The controversies over cloning are similar, except general public opinion in most countries stands in opposition to reproductive cloning. Some proponents of therapeutic cloning predict the production of whole bodies, lacking consciousness, for eventual brain transplantation.
Replacement of biological (susceptible to diseases) organs with mechanical ones could extend life. This is the goal of 2045 Initiative.
For cryonicists (advocates of cryopreservation), storing the body at low temperatures after death may provide an “ambulance” into a future in which advanced medical technologies may allow resuscitation and repair. They speculate cryogenic temperatures will minimize changes in biological tissue for many years, giving the medical community ample time to cure all disease, rejuvenate the aged and repair any damage that is caused by the cryopreservation process.
Many cryonicists do not believe that legal death is “real death” because stoppage of heartbeat and breathing—the usual medical criteria for legal death—occur before biological death of cells and tissues of the body. Even at room temperature, cells may take hours to die and days to decompose. Although neurological damage occurs within 4–6 minutes of cardiac arrest, the irreversible neurodegenerative processes do not manifest for hours. Cryonicists state that rapid cooling and cardio-pulmonary support applied immediately after certification of death can preserve cells and tissues for long-term preservation at cryogenic temperatures. People, particularly children, have survived up to an hour without heartbeat after submersion in ice water. In one case, full recovery was reported after 45 minutes underwater. To facilitate rapid preservation of cells and tissue, cryonics “standby teams” are available to wait by the bedside of patients who are to be cryopreserved to apply cooling and cardio-pulmonary support as soon as possible after declaration of death.
No mammal has been successfully cryopreserved and brought back to life, with the exception of frozen human embryos. Resuscitation of a postembryonic human from cryonics is not possible with current science. Some scientists still support the idea based on their expectations of the capabilities of future science.
Strategies for Engineered Negligible Senescence (SENS)
Another proposed life extension technology would combine existing and predicted future biochemical and genetic techniques. SENS proposes that rejuvenation may be obtained by removing aging damage via the use ofstem cells and tissue engineering, removal of telomere-lengthening machinery, allotopic expression of mitochondrial proteins, targeted ablation of cells, immunotherapeutic clearance, and novel lysosomal hydrolases.
While many biogerontologists find these ideas “worthy of discussion” and SENS conferences feature important research in the field, some contend that the alleged benefits are too speculative given the current state of technology, referring to it as “fantasy rather than science”.
Gene therapy, in which nucleic acid polymers are delivered as a drug and are either expressed as proteins, interfere with the expression of proteins, or correct genetic mutations, has been proposed as a future strategy to prevent aging.
A large array of genetic modifications have been found to increase lifespan in model organisms such as yeast, nematode worms, fruit flies, and mice. As of 2013, the longest extension of life caused by a single gene manipulation was roughly 150% in mice and 10-fold in nematode worms.
In The Selfish Gene, Richard Dawkins describes an approach to life-extension that involves “fooling genes” into thinking the body is young. Dawkins attributes inspiration for this idea to Peter Medawar. The basic idea is that our bodies are composed of genes that activate throughout our lifetimes, some when we are young and others when we are older. Presumably, these genes are activated by environmental factors, and the changes caused by these genes activating can be lethal. It is a statistical certainty that we possess more lethal genes that activate in later life than in early life. Therefore, to extend life, we should be able to prevent these genes from switching on, and we should be able to do so by “identifying changes in the internal chemical environment of a body that take place during aging… and by simulating the superficial chemical properties of a young body”.
Reversal of informational entropy
According to some lines of thinking, the ageing process is routed into a basic reduction of biological complexity, and thus loss of information. In order to reverse this loss, gerontologist Marios Kyriazis suggested that it is necessary to increase input of actionable and meaningful information both individually (into individual brains), and collectively (into societal systems). This technique enhances overall biological function through up-regulation of immune, hormonal, antioxidant and other parameters, resulting in improved age-repair mechanisms. Working in parallel with natural evolutionary mechanisms that can facilitate survival through increased fitness, Kryiazis claims that the technique may lead to a reduction of the rate of death as a function of age, i.e. indefinite lifespan.
One hypothetical future strategy that, as some suggest, “eliminates” the complications related to a physical body, involves the copying or transferring (e.g. by progressively replacing neurons with transistors) of a conscious mind from a biological brain to a non-biological computer system or computational device. The basic idea is to scan the structure of a particular brain in detail, and then construct a software model of it that is so faithful to the original that, when run on appropriate hardware, it will behave in essentially the same way as the original brain. Whether or not an exact copy of one’s mind constitutes actual life extension is matter of debate.