Why we have a finite lifespan is a question that has yet to be fully answered. While many theories have been investigated, research is now focused on a few promising theories that may provide the answer. The big question facing researchers is an uncertainty about the number of biological processes that affect aging. Some researchers believe that only a few fundamental processes are needed to explain aging. Others suspect there may be hundreds of processes involved and that a full understanding will remain elusive.
The earliest evidence that lifespan could be significantly extended came from observing that certain single gene mutations led to a longer life. While these mutations rarely resulted in a net positive for the organism, they did show a possibility for extending lifespan. The most promising discovery has been that calorie restriction resulted in a longer lifespan without diminishing quality of life if the minimum nutrient needs were met. In essence, staying trim has remarkable longevity and quality of life benefits. Others have shown that occasional fast provide remarkable benefits. More recently, Dr Valter Longo’s research with the fasting-mimicking diet has added to our understanding of why limiting calories is good for quality of life and longevity.
Today, a far more robust understanding of what affects aging is understood in terms of DNA damage, cross linking of proteins, oxidative stress, and more. For an overview of some of these theories both past and present read “Theories of Aging.”
While some of these theories would require a deep knowledge in multiple disciplines to fully appreciate, several of the most important factors are not complicated. For example, lifestyle is now understood to be a significant controllable factor influencing longevity. In other words, what you eat, how much you exercise, how you manage stress, the quality of your social interactions, and environmental influences have perhaps the greatest effect aside from genetic variations.
While genetics is a factor in longevity it only account for 20 to 30 percent of an individual’s chance of surviving to age 85. Most importantly, while you may inherit certain genetic variations that predispose you to disease or decreased longevity, most also have other gene variants that can provide disease resistance and longevity enhancement when supported by a healthy lifestyle.
If you happen to have been fortunate enough to inherit excellent longevity genes, then lucky you. Just be aware that the best genetics is no match for poor lifestyle choices. On the other hand, if dealt a genetic predisposition to disease, you still have a lot of good genes to work with. Often, proper signaling via lifestyle choices is enough to turn off the genes that could have otherwise resulted in a shortened life or a low quality of life.
At each stage of life and especially as we grow older, attention to lifestyle is where we get the best opportunities for determining our future health outcomes. Unfortunately, the current acute care medical system usually deals with each disease in isolation. Rather than treating the root cause of the underlying biological processes that have run amuck, powerful drug are often used in a whack-a-mole fashion. The result is that a person often gets cured of one disease only to develop another one soon after. The better treatment is one that first assesses the effects of lifestyle on health. This involves possible imbalances in all of the aforementioned lifestyle issues including a person’s mental outlook. For example, having a good diet is important but insufficient for quality of life if not living with purpose and gratitude. Similarly, brain fitness is unlikely without quality sleep and physical fitness. Taken together, all of these factors are interrelated as are factors like toxic exposure and stress management.
How long you will live and with what quality of life is a complex interaction between genetics, environment, lifestyle, and personality. While none of us knows our expiration date, knowing that regardless of age, there are many evidence-based strategies that can help stack the odds in our favor is a very encouraging message.
Nancy Neighbors, MD
The Many Theories of Aging
While many theories of aging have been proposed there is little consensus on which ones are the most important. Many of the proposed theories overlap to some extent.
Perhaps the most widely accepted overall theory of aging is the evolutionary senescence theory which focuses on the failure of natural selection to affect late life traits. In essence, evolution selected traits that make us strong and productive in our youth but failed to program in traits to protect us as we age.
The wear and tear theory suggests that cells and tissues have vital parts that wear out like components of an aging car might wear out from repeated use. While this theory seems plausible, the exceptions where a person lives to 110 suggest that there is far more to aging than this simple explanation.
The stem cell theory of aging postulates that the aging process is the result of the inability of various types of stem cells to continue to replenish the tissues of an organism with functional differentiated cells capable of maintaining that tissue’s original function. Quite an industry has risen to the challenge with remarkable success in treating some conditions. Typically, stem cell replacement therapies are quite expensive. For most, an intensive lifestyle change is a far more effective way to get a similar benefits.
The free radical theory of aging suggest that organisms age because cells accumulate free radical damage over time. A free radical is any atom or molecule that has a single unpaired electron in an outer shell. To counteract free radicals the body uses antioxidants that it makes along with antioxidant from plant-based foods.
The rate of living theory suggest that the greater an organism’s rate of oxygen basal metabolism, the shorter its life span.
The cross-linking theory of aging proposes that an accumulation of cross-linked proteins damage cells and tissues.
The somatic DNA damage theory suggest that as we age the normal DNA repair mechanisms cannot correct defects as fast as they are produced. Everyday our body suffers millions of occurrences of DNA damage. Ideally, the damaged cells are quickly removed by the immune system.
The immunological theory of aging suggests that aging is a mild and generalized form of a prolonged autoimmune phenomenon. The immune system changes that accompany old age may be a root cause for aging or just a symptom.
The hormone theory of aging suggests that the endocrine system controls aging. Synthetic human growth hormone (HGH) has been touted as a potential fountain of youth, with proponents hoping it can stave off the decline in tissue growth from aging, but research does not support its use for anti-aging.
The membrane theory of aging suggests that age-related changes in the cell’s ability to transfer chemicals, heat, and electrical processes impair it. As we grow older the cell membrane becomes less lipid (less watery and more solid). This impedes its efficiency to conduct normal function.
The mitochondrial decline theory suggests that enhancement and protection of the cell’s mitochondria is an essential part of preventing and slowing aging. To some degree, enhancement can be achieved with certain nutrients.
The information theory of aging suggests that we age and become susceptible to diseases because our cells lose useful information. Whereas DNA stores information discreetly, somewhat like a computer, in a near error free format, our epigenome is stored in a more error prone analog format. An analogy would be a DVD player that over time accumulates scratches so that information can no longer be read correctly. The book, “Lifespan – Why we Age – and Why We Don’t Have To” by David Sinclair, PhD provides examples of studies with animals that demonstrate remarkable possibilities for extending lifespan and healthspan. For an interesting overview of the theory, click here.
For now, these many theories remain controversial. In a way, the current situation is reminiscent of the Blind Men and the Elephant parable. Like the blind men that could only inspect the elephant by touch, scientists today also have limited ability to investigate and understand the complexities of cells and the external forces upon them. Complicating the diversity of theories is the evolving nature of scientific understanding. Often one theory morphs into another and yet both remain viable in some context. For example, in the previous century we learned that the Theory of Relativity was quite a nice improvement over Newton’s Laws of Motion, first published in 1687, Today, both theories have their place. By evidence that planes still fly and buildings aren’t falling down, we still accept Newton’s theory as adequate in many applications. Similarly, the need for multiple theories of aging will last for quite some time. For now, we wait. Perhaps the answer will come as computers become faster. Perhaps serendipity will help another genius sort it out. Fortunately, our understanding of cells is advancing rapidly, and there is no shortage of great minds focused on the problem.
The good news is that while science inches along, hundreds of studies already demonstrate that we don’t have to wait. Positive lifestyle change is a significant factor for helping us live longer, enjoy a better quality of life, and age gracefully – and it’s something we can do today.
More About Why
Quality Sleep is Important
If previous articles about sleep left you with questions, you can find additional information about recent sleep research in a three part podcast by Dr. Peter Attia in which he interviews Dr. Matthew Walker, author of the book, “Why We Sleep.”
Part I: Dangers of poor sleep, Alzheimer’s risk, mental health, memory consolidation, and more
Part II: Heart disease, cancer, sexual function, and the causes of sleep disruption (and tips to correct it)
Part III: The penetrating effects of poor sleep from metabolism to performance to genetics, and the impact of caffeine, alcohol, THC, and CBD on sleep
What’s for Dinner?
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