Telomeres and Ageing: What the Science Shows
- , by SANUSq Research team
- 13 min reading time
Few topics in biology attract as much attention as telomeres and ageing. These tiny caps on the ends of our chromosomes have become a symbol of the body's clock, and a whole market of supplements and tests has grown up around the idea of winding that clock back. Here is what telomeres actually are, what seems to protect them, and why a healthy dose of scepticism is the best response to products that promise to lengthen them.
What are telomeres?
Telomeres are stretches of repeated DNA at the very ends of each chromosome. They protect the genetic information inside, rather like the plastic tips on a shoelace that stop it fraying.
Each time most cells divide, a little of the telomere is lost, so telomeres gradually get shorter over a lifetime. When they become too short, the cell can no longer divide properly and enters a resting state called senescence, or dies. Oxidative stress and long-running inflammation appear to speed this telomere shortening up, which is one reason telomeres are so often linked with wear and tear on the body.
An enzyme called telomerase can rebuild telomeres. The discovery of how telomeres and telomerase protect chromosomes earned Elizabeth Blackburn, Carol Greider and Jack Szostak the Nobel Prize in Physiology or Medicine in 2009. Telomerase is active in some cells, such as stem cells and reproductive cells, but it is kept switched down in most of the cells in our body. As we will see, that tight control is not an accident.
Telomeres and ageing: what the science shows
Telomere length is now seen as a marker of cellular ageing. On average, people with shorter telomeres are older and have a higher risk of some age-related diseases. That is a robust and genuinely interesting finding.
In a review in a leading science journal, Blackburn et al. (2015) described how greater telomere shortening predicts mortality and age-related diseases, both in people with rare inherited telomere disorders and in the general population. They also noted that telomere maintenance is shaped by genetic factors as well as by non-genetic influences across life, and that the two interact.
A systematic review and meta-analysis by Haycock et al. (2014), covering 24 studies and more than 43,000 people, found that those in the shortest third for white blood cell telomere length had about a 54% higher risk of coronary heart disease than those in the longest third. The link with stroke was less certain. These were observational studies, so they show an association, not cause and effect.
Reading these findings needs care. A marker is not the same as a cause. The fact that short telomeres travel alongside ageing does not prove that making them longer would make us younger or help us live longer. It's the difference between reading the hands of a watch and believing that turning them changes the time.
Two important caveats
First, genetics plays a large part in the telomere length we start with, regardless of how we live.
Second, the direction of the relationship is not always clear. Is telomere shortening a driver of ageing, or mainly a record of it? Current thinking is that it is probably a bit of both, which is a good reason to be wary of marketing shortcuts.
Genetic studies help untangle cause and effect. Using inherited gene variants that influence telomere length, Kuo et al. (2019) studied around 380,000 UK Biobank participants. Genetically longer telomeres were linked with a slightly lower risk of coronary heart disease but a higher risk of cancer, and showed little association with parental lifespan, cognitive function, grip strength or falls. The authors concluded that lengthening telomeres may offer little gain in later-life health.
Lifestyle and telomere shortening: what the research links
This is the best-supported part of the story, and the least dramatic. The strongest associations with healthier telomeres come from everyday habits. Most of the evidence is observational, so it shows links rather than proof, but the pattern is consistent.
Regular physical activity
A meta-analysis of randomised controlled trials by Sun et al. (2025) found that exercise programmes were associated with better maintenance of telomere length and higher telomerase activity than control conditions. Aerobic exercise showed the most consistent effect on telomerase, effects needed at least 16 weeks to appear, and results varied widely between studies, partly because of differences in how telomeres were measured.
Not smoking
In a systematic review of 84 studies, Astuti et al. (2017) found that people who had ever smoked had shorter telomeres on average than people who had never smoked, and that more pack-years of smoking went with shorter telomeres. The average difference was small, and the studies varied.
A Mediterranean-style diet
Eating patterns rich in vegetables, fruit, pulses, wholegrains, fibre, nuts, olive oil and fish supply a wide range of dietary antioxidants and tend to go with healthier markers of all kinds.
A meta-analysis of eight cross-sectional studies in nearly 14,000 people by Canudas et al. (2020) found that closer adherence to a Mediterranean diet was associated with longer telomeres. The effect was modest, and the authors called for larger prospective studies and trials to confirm it.
Managing stress
Long-term stress is thought to wear on cells through inflammation and oxidative stress. Practices such as mindfulness have been studied, though the evidence is still developing.
Pooling 22 studies in nearly 9,000 people, Mathur et al. (2016) found that higher perceived stress was associated with a very small reduction in telomere length. The authors cautioned that publication bias may have inflated the result, and that long-term chronic stress could matter more than the short-term stress most studies measured.
Sleeping enough and keeping to a healthy weight round out the list; obesity has also been associated with shorter telomeres. None of this is new, and that is precisely the point. The habits linked with healthier telomeres are the same ones that support your health in general, and they need no pills at all.
How to lengthen telomeres? The supplement question
This is where caution matters most. Some supplements, sold as "telomerase activators", are marketed as anti-ageing products. The best known, TA-65, is derived from astragalus root and has been tested in a placebo-controlled trial.
In a one-year randomised, double-blind trial in 117 adults aged 53–87, Salvador et al. (2016) reported that the lower dose of TA-65 increased telomere length while the placebo group lost length. The higher dose did not differ significantly from placebo. The study was funded by the product's manufacturer, and several authors were employees of, or consultants to, the company.
Does this mean telomeres can be lengthened in a way that matters? Not on current evidence, for three reasons.
- The trials are few and small, and they are often linked to the companies selling the product. Mixed results, such as a lower dose working better than a higher one, call for more caution, not less.
- Changing a marker is not the same as a health benefit. No robust study shows that any supplement helps people live longer or healthier lives by lengthening telomeres.
- There is a genuine safety question. Telomerase is the very enzyme that cancer cells hijack to keep dividing indefinitely. Boosting it artificially raises a theoretical cancer concern that research has not ruled out.
A large genetic analysis by Haycock et al. (2017), covering 35 cancers and 48 other diseases, found that genetically longer telomeres were generally associated with a higher risk of several cancers, including melanoma, lung adenocarcinoma and glioma, while being linked with a lower risk of some other conditions such as coronary heart disease. In other words, longer is not simply better.
In plain terms: no over-the-counter supplement has been shown to lengthen telomeres in a way that is safe, reliable and beneficial for health in humans. If you are considering a telomerase activator, speak to your doctor first, particularly if you have had cancer or have a family history of it.
Why all the excitement?
Telomeres offer an irresistible story: one number that sums up your "real" age, and one molecule that can change it. The biology is far more tangled. Ageing involves dozens of processes, and telomeres are only one piece. Focusing on them to the point of buying expensive courses of supplements risks missing the wood for the trees.
Are telomere tests worth it?
Tests claiming to measure your "biological age" from telomere length are widely sold. Their practical value for individuals is very limited at present. Results can vary between laboratories and from one sample to the next, different methods don't always agree, a single figure is hard to interpret for one person, and it almost never changes medical care. A "reassuring" or "worrying" result gives you little you can act on, apart from anxiety or a sales pitch.
That doesn't make telomere measurement worthless. In research, across large groups of people, it is a valuable tool. For you as an individual, though, standard health checks such as blood pressure, activity levels, weight and diet tell you far more than a telomere score.
The bottom line
Telomeres are a fascinating area of science and a useful marker of cellular ageing. But their "secret" is disappointingly simple: what looks after them is what looks after everything else. Move regularly, eat well, don't smoke, sleep enough and manage stress. Pills that promise to rewind the cellular clock rest on thin evidence and raise real safety questions. Faced with a promise as appealing as "lengthen your telomeres", healthy scepticism is the best reflex.
Frequently asked questions
Can you lengthen your telomeres?
A few supplements, such as TA-65, have shown a measurable increase in small, industry-funded studies. There is no evidence that this translates into better health or a longer life, and long-term safety has not been established. Regular exercise is associated with better telomere maintenance.
Can a supplement reverse ageing?
No. No supplement has been shown to reverse ageing in humans. Lengthening a biological marker is not the same as becoming younger, so be wary of anything sold as a fountain of youth in capsule form.
What causes telomere shortening?
Telomeres shorten naturally each time cells divide, so age is the main factor, and genetics sets much of your starting length. Smoking, long-term stress, obesity, inflammation and oxidative stress have all been associated with faster shortening.
Do antioxidants protect telomeres?
Oxidative stress is linked with faster telomere shortening, and diets rich in fruit and vegetables, and therefore in dietary antioxidants, are associated with healthier cellular markers. But it is the overall diet that counts, not a single isolated molecule in a capsule.
Are telomerase activators safe?
There is a real open question. Telomerase is the enzyme cancer cells exploit to keep multiplying, so stimulating it carries a theoretical risk that has not been ruled out. Talk to your doctor before considering this kind of product, and be particularly cautious if you have a personal or family history of cancer.
Should I take a telomere test?
For most people, it adds little. Results vary between methods and laboratories, are hard to interpret for one person and rarely change medical care. Your time and money are better spent on the habits that support your health.
References
- Blackburn EH, Epel ES, Lin J. Human telomere biology: a contributory and interactive factor in aging, disease risks, and protection. Science. 2015;350(6265):1193–1198. PMID 26785477
- Haycock PC, Heydon EE, Kaptoge S, Butterworth AS, Thompson A, Willeit P. Leucocyte telomere length and risk of cardiovascular disease: systematic review and meta-analysis. BMJ. 2014;349:g4227. PMID 25006006
- Kuo CL, Pilling LC, Kuchel GA, Ferrucci L, Melzer D. Telomere length and aging-related outcomes in humans: a Mendelian randomization study in 261,000 older participants. Aging Cell. 2019;18(6):e13017. PMID 31444995
- Sun L, Zhang T, Luo L, Yang Y, Wang C, Luo J. Exercise delays aging: evidence from telomeres and telomerase — a systematic review and meta-analysis of randomized controlled trials. Frontiers in Physiology. 2025;16:1627292. PMID 40642293
- Astuti Y, Wardhana A, Watkins J, Wulaningsih W; PILAR Research Network. Cigarette smoking and telomere length: a systematic review of 84 studies and meta-analysis. Environmental Research. 2017;158:480–489. PMID 28704792
- Canudas S, Becerra-Tomás N, Hernández-Alonso P, et al. Mediterranean diet and telomere length: a systematic review and meta-analysis. Advances in Nutrition. 2020;11(6):1544–1554. PMID 32730558
- Mathur MB, Epel E, Kind S, et al. Perceived stress and telomere length: a systematic review, meta-analysis, and methodologic considerations for advancing the field. Brain, Behavior, and Immunity. 2016;54:158–169. PMID 26853993
- Salvador L, Singaravelu G, Harley CB, Flom P, Suram A, Raffaele JM. A natural product telomerase activator lengthens telomeres in humans: a randomized, double blind, and placebo controlled study. Rejuvenation Research. 2016;19(6):478–484. PMID 26950204
- Telomeres Mendelian Randomization Collaboration; Haycock PC, Burgess S, Nounu A, 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. PMID 28241208
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