Telomeres: What the Latest Science Says About Aging at the Ends of Our Chromosomes
By Kevin Wallace, DVM, DACVIM | Mindful Living Sanctuary | October 2026
Telomeres are the protective caps on the ends of our chromosomes, and they gradually shorten as we age. Shorter telomeres are linked to heart disease and other age-related conditions, and the same habits that support overall health, including exercise, a whole-food diet, good sleep, and managing stress, are associated with slower shortening. But the science is more nuanced than the headlines: longer isn’t always better, and consumer telomere tests aren’t very useful.
Telomeres have become one of the most talked-about topics in the science of aging, and for good reason. In this article I’ll explain what they are, why they matter, what the research actually shows about slowing their decline, where the benefits stop, and where the hype has gotten ahead of the evidence.
What telomeres are
Each of our 46 chromosomes has a telomere at each end: a stretch of the same short DNA sequence, TTAGGG, repeated thousands of times. The usual comparison is the plastic tip on a shoelace. Telomeres don’t carry genes. Their job is to protect the genes, keeping chromosome ends from fraying, fusing together, or being mistaken by the cell for broken DNA.
The problem is that the machinery that copies our DNA can’t copy all the way to the very end of a chromosome. So each time a cell divides, its telomeres get a little shorter. A typical cell loses somewhere on the order of 30 to 200 base pairs of telomere with each division, and telomeres shrink from roughly 8,000 to 10,000 base pairs at birth toward a few thousand in older adults. Those are population ranges, not a personal clock.
Some cells can rebuild their telomeres using an enzyme called telomerase, which adds TTAGGG repeats back onto the ends. Stem cells and some immune cells use it. Most ordinary body cells keep it switched off. The discovery of how telomeres and telomerase protect chromosomes earned Elizabeth Blackburn, Carol Greider, and Jack Szostak the 2009 Nobel Prize in Physiology or Medicine.
Why they shorten, and why it matters
When a cell’s telomeres get critically short, the cell stops dividing. It either dies or becomes senescent, a kind of zombie state in which it lingers, no longer doing its job and releasing inflammatory signals that affect the tissue around it. As senescent cells accumulate, tissues lose their ability to repair and renew themselves. Telomere attrition is one of the recognized hallmarks of aging (1).
In large population studies, shorter telomeres in white blood cells are associated with higher risk of cardiovascular disease and death from all causes. Genetic studies back up a causal role for at least some of these: people who inherit gene variants for longer telomeres have lower rates of coronary heart disease and abdominal aortic aneurysm (2).
At the extreme end, people born with rare mutations that make telomeres very short develop short telomere syndromes: early gray hair, bone marrow failure, lung scarring, and liver disease. They show clearly what happens when telomeres run out. That is a diagnosis for a specialist, not a reading on a wellness app.
It’s important to understand that telomere length varies enormously between people from birth, largely because of genetics. A single measurement tells you much less about your own aging than the population studies might suggest.
The twist: longer isn’t always better
If short telomeres are bad, surely longer is better? Not necessarily, and this is one of the most important developments in the field.
Telomere shortening isn’t just a flaw. It’s also one of the body’s built-in defenses against cancer. It limits how many times a cell can divide, which puts a brake on cells that start to grow out of control. Most cancers get around that brake by switching telomerase back on.
The genetic evidence. A 2017 Mendelian randomization analysis, using genetic data across hundreds of thousands of cases, found that genetically longer telomeres were associated with lower risk of coronary heart disease and abdominal aortic aneurysm, and higher risk of several cancers. The cancer associations included glioma, lung adenocarcinoma, melanoma, bladder cancer, and kidney cancer (2). The authors’ conclusion was plain: longer telomeres likely increase risk for several cancers and reduce risk for some non-cancer diseases, including cardiovascular disease.
The long telomere syndrome. In 2023, Johns Hopkins researchers led by Dr. Mary Armanios described families carrying mutations in a gene called POT1 that cause abnormally long telomeres. These families had high rates of clonal blood disorders and a range of cancers, because cells with very long telomeres keep dividing and accumulating mutations that would otherwise be held in check (3).
The lesson: the goal isn’t the longest possible telomeres. It’s avoiding the premature loss of telomeres from an unhealthy lifestyle, while letting the body’s own regulation do its job. That’s why I’m wary of any product that promises to switch on telomerase.
What the research says helps
Here’s the evidence for what can slow telomere shortening, strongest first, with the limit on each one.
1. Aerobic exercise. This has some of the best evidence, including a randomized trial. German researchers assigned 124 previously inactive middle-aged adults to endurance training, high-intensity interval training, resistance training, or no added exercise for six months, three 45-minute sessions a week. Endurance and interval training raised telomerase activity in immune cells two- to three-fold and lengthened telomeres in lymphocytes and leukocytes. Resistance training improved fitness and did not lengthen telomeres (4). Strength training has many other benefits, including the muscle and balance we need to stay independent, so the take-home is to do both, not to skip the weights. The drawback of treating this as a telomere prescription is injury from a sudden program. The trial used people who had been inactive. Start where you are.
2. Vitamin D. In 2025, a sub-study of the large VITAL trial followed adults over 50, men 50 and older and women 55 and older, for four years. Those taking 2,000 IU of vitamin D3 daily lost about 140 fewer base pairs of leukocyte telomere length than those taking a placebo. The investigators estimated that difference as nearly three years of aging. Omega-3 supplements in the same trial had no significant effect on telomeres (5). It is the strongest randomized evidence yet for any supplement, and it is still a soft result. The p-value was 0.039. No health outcomes were measured in the telomere paper. The parent VITAL trial did not show that this dose of vitamin D prevented cancer or cardiovascular disease in the whole study population. Johns Hopkins telomere expert Dr. Mary Armanios has also noted that the difference sits within the normal range of human variation, and that the measurement method used, qPCR, is the least reproducible of the available techniques (6). I still take vitamin D, guided by a blood level, for bone and for the latitude we live at. I do not take it because a telomere sub-study proved it slows aging.
3. Omega-3 fatty acids. The evidence is mixed, and the larger trial lost. A small four-month study found that what tracked with telomere change was how much omega-3 actually built up in blood cells, not the dose on the label. The VITAL trial, which is the one built to answer the question, found no effect of 1 gram a day of marine omega-3s on telomere length at two years or four (5). Omega-3s may still earn a place for other reasons. They have not earned a telomere claim.
4. A whole-food, plant-rich diet. In the Harvard Nurses’ Health Study, women who ate closest to a Mediterranean diet had longer telomeres (7). That is observational. Women who eat that way differ in other habits too. Diets high in processed foods and sugary drinks go the other way. In a national survey analysis, daily consumption of a 20-ounce sugar-sweetened soda was associated with telomere shortening the authors calculated as about 4.6 years of extra aging, on the order of the association seen with smoking (8). That study was cross-sectional, one snapshot, not proof that soda shortens telomeres by that amount. Diet soda was not associated. The practical reading is the same one the rest of this series supports: the sugary drink is the habit to drop, not a number to fear.
5. Comprehensive lifestyle change. In a small, widely cited pilot, Dr. Dean Ornish followed men with low-risk prostate cancer who had chosen active surveillance. Ten men who adopted a plant-based diet, exercise, stress management, and social support were compared with 25 external controls. Over five years, relative telomere length rose in the lifestyle group and fell in the controls. Adherence tracked with the change. Telomerase activity at five years did not differ (9). Secondary accounts often summarize the length change as about 10 percent. It is a tiny study, not randomized, with controls drawn from outside the intervention. It is consistent with everything else. It is not proof that the program lengthens telomeres in general.
6. Managing stress, and sleep. In a 2004 study, Elissa Epel and Elizabeth Blackburn compared healthy premenopausal women. Those with the highest perceived stress had telomeres shorter by the equivalent of at least one decade of additional aging, along with lower telomerase activity and higher oxidative stress (10). The sample was 58 women, 39 of them caring for a chronically ill child. It is a landmark paper, and it is not a large trial. Aerobic exercise appears to buffer some of that stress-related loss in later work from the same group. Meditation practices have been linked with higher telomerase activity in small studies. Short and poor-quality sleep is associated with shorter telomeres in observational studies. None of this means a meditation app is a telomere drug. It means chronic, unrelieved stress and short sleep belong on the same list as smoking.
A caution on all of this: apart from the exercise trial and the vitamin D sub-study, most of the evidence is observational or comes from small studies. The consistency is encouraging. The effects are modest. Leukocyte telomere length is a research marker. It is not a vital sign.
What shortens them
The same things that damage health in general are linked to faster telomere loss, largely through oxidative stress and chronic inflammation:
• Smoking, one of the most consistent associations.
• Obesity and insulin resistance.
• Chronic psychological stress, as the Epel and Blackburn study shows.
• Sugary drinks and ultra-processed food.
• Physical inactivity.
• Poor sleep.
• Air pollution and toxic exposures, which increase oxidative stress.
In other words, many of the topics in this series, from ultra-processed foods to air quality and glutathione, connect to the health of our telomeres. The connection is biological plausibility plus association. It is not a claim that fixing the compost pile will lengthen your telomeres.
Heat, sauna, and heat shock proteins
Heat stress belongs in a neighboring chapter, not in the telomere chapter as a proven tool.
When the body is exposed to heat, from a sauna, a hot bath, or hard exercise, cells produce heat shock proteins. These act as chaperones, helping other proteins fold correctly and repairing proteins damaged by stress. Finnish cohort studies link frequent sauna use with lower cardiovascular and overall mortality. Brief heat exposure extends lifespan in worms and flies. Those are real findings, and they are about cardiovascular risk and protein handling, not about measured telomere length.
Heat stress and telomeres are two separate branches of aging biology. Heat shock proteins protect proteostasis, the cell’s ability to keep its proteins in working order, which is another of the hallmarks of aging (1). I have not found good human evidence that sauna use itself lengthens telomeres. Heat and telomeres share the same themes: less oxidative damage, less inflammation, and better cellular repair. Exercise delivers both at once, which is one more reason it tops the list.
If you use a sauna, stay hydrated, avoid alcohol, and talk with your doctor first if you have heart disease or low blood pressure. The drawback of selling sauna as a telomere treatment is that the telomere evidence is not there.
Telomere tests and telomerase supplements: worth it?
Consumer telomere tests. Several companies sell telomere length tests. I don’t recommend them for most people. Telomere length varies so much between individuals from birth that one number tells you little. Most tests use qPCR, which Dr. Armanios describes as the least reproducible of the ways telomeres can be measured, sensitive even to how and when a sample was collected (6). And there’s no treatment a result would change: the advice is the same whatever your number. Clinical telomere testing does have a real place in diagnosing the rare short telomere syndromes. That is a different test, ordered for a different reason.
Telomerase activators. Supplements such as TA-65, made from astragalus root, are marketed to switch on telomerase and lengthen telomeres. The human evidence is limited to small, short studies, often funded by the companies selling the extract. Given what we now know about long telomeres and cancer, I’m cautious about deliberately switching on telomerase with a pill. The benefit is unproven. The theoretical harm is the one the POT1 families illustrate. I’d rather support the body’s own regulation with exercise, diet, sleep, and stress management.
Our approach
Nothing about protecting telomeres requires a special product. It’s the same foundation we’ve built this whole series on.
• We eat a whole-food, plant-based diet, heavy on vegetables, fruit, beans, and whole grains, with very few processed foods.
• I take vitamin D3, guided by blood tests, as I explained in our supplements article. The VITAL telomere result makes me more comfortable with that choice. It does not turn the supplement into an anti-aging drug.
• We work to lower our toxic load, from our water and cookware to the pesticides we don’t use on our land.
• Sulforaphane, as Avmacol, and a healthy glutathione system help keep oxidative stress in check, which is one of the drivers proposed for telomere loss. That is a mechanism, not a telomere trial.
Where I’m doing well, and where I’m not. I try to hold myself to the same honest standard I apply to the research.
• Activity and fresh air. Thea and I are both very active for our age. Running a permaculture property means we’re outside working most days, and that steady, all-day movement is the kind of activity the research favors.
• Winter is harder. In the winter months, outdoor work drops off, and I find myself spending too much time at the computer: writing these articles, editing videos, and handling planning and paperwork. Long hours of sitting are one of the lifestyle factors linked to faster telomere loss, so this is an area I’m working on.
• Red light therapy. Every winter day I spend about 15 minutes in front of a red light panel. I find it helpful during our dark northern winters, but I haven’t found good evidence that it affects telomeres, and I don’t count it as a substitute for exercise or daylight.
• Sleep is my biggest challenge. I’ve struggled with sleep for most of my life. During my years as a practicing veterinarian, three hours a night was typical, and four was a good night. Only recently have I been getting four to six hours, and since I started taking magnesium glycinate in the evening, some nights I reach about six, the most I’ve ever slept. That’s my own experience rather than proof, and the research on magnesium and sleep is modest, but for me it has made a real difference. Since short sleep is consistently associated with shorter telomeres and many other health risks, it’s the part of my own routine that most needs attention.
I share this because none of us does everything right, and seeing where the evidence points has helped me decide where to focus next.
Where we land
1. Telomeres protect our chromosomes, and they shorten with each cell division and with age.
2. Premature shortening is linked to heart disease and other age-related conditions, but longer isn’t always better. Very long telomeres raise cancer risk.
3. Aerobic exercise has the best evidence. Endurance and interval training raised telomerase activity and lengthened telomeres in a six-month randomized trial. Keep strength training too, for its other benefits.
4. Vitamin D slowed leukocyte telomere loss in a VITAL sub-study. The effect was modest, borderline, and not tied to a health outcome. It is not a reason to megadose.
5. Eat whole, plant-rich foods, and skip sugary drinks and ultra-processed foods. The soda finding is an association, not a sentence.
6. Manage stress, sleep well, and don’t smoke. The stress finding is real and comes from a small study.
7. Heat and sauna support cellular repair through heat shock proteins, a related pathway. Direct evidence for telomeres is lacking.
8. Skip consumer telomere tests and telomerase-activating supplements. The tests are unreliable for healthy people, and the pills are unproven, with a theoretical cancer risk.
The good news is that nothing on this list is exotic or expensive. The habits that protect our telomeres are the same ones that protect our hearts, brains, and overall health.
References
1. López-Otín C, Blasco MA, Partridge L, Serrano M, Kroemer G. The hallmarks of aging. Cell. 2013;153(6):1194-1217. cell.com
2. Telomeres Mendelian Randomization Collaboration; Haycock PC, Burgess S, et al. Association between telomere length and risk of cancer and non-neoplastic diseases: a Mendelian randomization study. JAMA Oncology. 2017;3(5):636-651. jamanetwork.com
3. DeBoy EA, Tassia MG, Schratz KE, et al. Familial clonal hematopoiesis in a long telomere syndrome. New England Journal of Medicine. 2023;388(26):2422-2433. nejm.org
4. Werner CM, Hecksteden A, Morsch A, et al. Differential effects of endurance, interval, and resistance training on telomerase activity and telomere length in a randomized, controlled study. European Heart Journal. 2019;40(1):34-46. Oxford Academic
5. Zhu H, Manson JE, Cook NR, et al. Vitamin D3 and marine omega-3 fatty acid supplementation and leukocyte telomere length: 4-year findings from the VITamin D and OmegA-3 TriaL (VITAL). American Journal of Clinical Nutrition. 2025. sciencedirect.com
6. Scientific American. Vitamin D May Slow Cells’ Aging by Protecting DNA (includes comment from Mary Armanios). May 2025. scientificamerican.com
7. Crous-Bou M, Fung TT, Prescott J, et al. Mediterranean diet and telomere length in Nurses’ Health Study: population based cohort study. BMJ. 2014;349:g6674. bmj.com
8. Leung CW, Laraia BA, Needham BL, et al. Soda and cell aging: associations between sugar-sweetened beverage consumption and leukocyte telomere length. American Journal of Public Health. 2014;104(12):2425-2431. ajph.org
9. Ornish D, Lin J, Chan JM, et al. Effect of comprehensive lifestyle changes on telomerase activity and telomere length in men with biopsy-proven low-risk prostate cancer: 5-year follow-up of a descriptive pilot study. Lancet Oncology. 2013;14(11):1112-1120. thelancet.com
10. Epel ES, Blackburn EH, Lin J, et al. Accelerated telomere shortening in response to life stress. Proceedings of the National Academy of Sciences. 2004;101(49):17312-17315. pnas.org
