WHEN David Nurse turned 30, he wanted to find out how his biological age compared with his chronological one. A life coach with the US National Baseball Association, he hoped that the ultra-healthy lifestyle he advocates to players had kept his own body young and healthy, too. So he took a test to assess the length of his telomeres. It revealed his biological age to be 28 years. That was in 2017. Two years later, he took another test. “I was down to 25, so that was great,” he says.
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If you google “telomeres”, you are likely to find them described as an ageing clock. They are segments of DNA at the ends of each chromosome that become shorter every time a cell divides. If this shortening happens slowly, it suggests that your body is wearing well. Say you are a 60-year-old with telomeres as long as those of an average 50-year-old, your mortality risk is equivalent to that of someone 10 years younger – or so the story goes. Increasing numbers of people want this information, and many companies offer tests like the one Nurse took, together with various pills claimed to lengthen your telomeres and, in turn, your lifespan.
If only it were that simple. We are now discovering that telomeres are an unreliable ageing clock, which raises questions about the validity of ageing tests based on them. The links between telomere length and lifestyle choices also aren’t as straightforward as we once thought. In fact, long telomeres can even be bad news. Nevertheless, there are some surprising ways we can look after our telomeres.
At first glance, telomere-mania seems grounded in science. In 1982, Elizabeth Blackburn at the University of California, Berkeley, and Jack Szostak at Harvard Medical School cracked the riddle of how chromosomes remain intact when cells divide: they have repeating units of DNA at their ends that stop them from unravelling. The pair called these “telomeres”. Later, they discovered that each time a cell divides, its telomeres become shorter, like the ticking of a biological clock. Meanwhile, Blackburn and Carol Greider at Cold Spring Harbor Laboratory in New York identified an enzyme, telomerase, that promotes the construction of telomere DNA.
These discoveries won Blackburn, Greider and Szostak a Nobel prize in 2009. Hype soon followed and researchers began piling into the field. However, as we find out more about telomeres, the mythology that has built up around them is starting to crumble.
For a start, it turns out that having long telomeres isn’t necessarily a sign that you have done a great job keeping your body younger and healthier than other people of your chronological age. A lot of the differences between people are down to genes. We now know that , with as much as 60 per cent of the variation between individuals being due to their genes. There are , and some of them are responsible for regulating the activity of telomerase.
What happens to a fetus while in the uterus also has a huge effect. Studies have linked shorter telomeres to such as phenols and phthalates, to smoking, air pollution, and to the mother being overweight.
Genes and prenatal conditions mean that some people are born with telomeres consisting of – the building blocks of DNA – while others have as many as 15,000. Considering that adults lose between about 30 and 50 base pairs of telomeres per year, this represents a huge difference at the start line.
That disparity can increase throughout early childhood. Fast growth and rapid cell replication mean that telomere length decreases quickly in this period. However, the rate varies enormously. From birth until the age of 4, children can of telomeres per year. One reason for this variation may be the adversity a child experiences. of more than 40 studies showed that poverty, abuse and maternal depression were among the factors linked to faster telomere shortening.
Where telomere length is concerned, most of our cards have been dealt before we finish primary school. Once we enter our second decade of life, telomere shortening slows. Thereafter, how our telomere length compares with that of other people of the same chronological age , according to research by Abraham Aviv at Rutgers New Jersey Medical School and his colleagues. His team measured the telomeres of 67 pre-teen children and their parents and ranked them in order of telomere length. Fourteen years later, the ranking remained unchanged for 90 per cent of them. “If you are in the 90th percentile of the distribution, you are likely going to stay there for the rest of your life,” says Aviv.
Not everyone is convinced that our telomere ranking barely budges over adulthood. Nevertheless, many do agree that popular methods touted to increase telomere length are often based on little more than hype. Despite what you might read online, for example, meditating for 15 minutes each day won’t make you five years younger, nor will eating broccoli with every meal – although, admittedly, both can be good for you. Even the much-vaunted effects of exercise are equivocal: only half of studies show positive links with telomere length, most of them weak.
“At birth, some people’s telomeres are a lot longer than those of others”
In fact, there is a lot of conflicting research. For example, one study may say that physically active people have longer telomeres for their age, but another will find no effects. The same goes for sleep quality and meditation. Even a healthy diet doesn’t always come out as good for your telomeres, despite . In 2019, for instance, that a Mediterranean diet has little effect on telomeres, while found that antioxidant intake isn’t associated with their length.
One reason for such inconsistencies is that telomere research has been the victim of its own success, with lots of the studies done by scientists who specialise in other areas. “They are just kind of excited about it, so they maybe publish one or two papers and then move on,” says Belinda Needham at the University of Michigan. The result has been that not all of the studies are of the highest standard.
There is another possible reason why lifestyle interventions often seem to have little effect on telomere length. In 2018, researchers studying European starlings were surprised to discover that birds with shorter telomeres tended to than those with longer telomeres. This prompted a provocative idea: that people with short telomeres may be more likely to adopt some unhealthy behaviours. A meta-analysis of published last year seems to back this up. Smokers do have shorter telomeres than non-smokers, but smoking itself has little impact on how fast your telomeres shorten. The researchers calculated that it would take 167 years of smoking to account for the telomere length differences between smokers and non-smokers. In other words, it looks like smokers have shorter telomeres in the first place, hinting that this might make them more prone to adopting the risky habit.
So, perhaps when it comes to telomere length and behaviour, we are getting cause and effect the wrong way around. Elissa Epel at the University of California, San Francisco, who co-authored a book called The Telomere Effect with Blackburn, believes researchers must explore this possibility. Causation could go in both directions, she says, and be far from simple. For example, there could be factors that drive both telomere shortening and a penchant for poor lifestyle choices, such as exposure to childhood adversity.
All this suggests that we shouldn’t necessarily base our lifestyle choices on the results from telomere research. And there is another reason we should be sceptical about these studies. Many use a method called qPCR to estimate telomere length. It is cheap and easy to use, but prone to measurement errors, from different labs. “qPCR still could be a very powerful method when you are dealing with 50,000 people,” says Aviv. “But the majority of studies that report findings of qPCR are limited – sometimes to several hundred people or even fewer – and those findings in my view are not very reliable.”
“People with shorter telomeres might be more likely to adopt risky behaviours”
Unreliable clock
Most commercial telomere tests use qPCR too. And, with a sample size of one – you – this unreliability is amplified. It is likely that if you got tested by two different labs, the results wouldn’t tally: a 40-year-old, for example, might be given a biological age of 35 from one test, and 55 from another. Then there is the problem of how those biological ages are derived from telomere length. Some companies, and some researchers, calculate “biological age” by comparing a subject’s average telomere length with that of a “typical person” of their chronological age. Others simply assume that a year equals somewhere between 30 and 50 base pairs and divide a person’s average telomere length by that number. With so much variability in people’s initial telomere length, some are beginning to question these calculations. “We are now suggesting that researchers do not talk about telomeres in terms of years of ageing, but rather report just the raw results,” says Epel.
Given all this, it is hardly surprising that some people are a little sceptical about commercially available telomere testing. “I don’t think that you can use it in any way that’s particularly meaningful for your health,” says Needham. “I personally wouldn’t recommend anyone to have that kind of testing done – I haven’t had it and I won’t.”
What is more, there is now a growing realisation that the whole “longer telomeres are better” idea is too simplistic. In 2017, research revealed that having genes associated with longer telomeres increases the risk of , including melanoma, ovarian and testicular cancer. The effect is particularly strong for some types of cancer, especially glioma, a type of brain tumour. The same study also showed that having long telomeres decreases your odds of developing cardiovascular disease, which might help explain what is going on. Evolutionary forces must make a trade-off to balance the risks of degeneration, which causes conditions like cardiovascular disease, against growth, and it looks like the enzyme telomerase is involved. As well as lengthening telomeres, telomerase also promotes cell growth — which isn’t a good thing if the cell in question is cancerous.
Anyone tempted to buy telomere-lengthening pills online should take note. According to Epel, studies on telomerase-activating supplements don’t tend to address the long-term risk of cancer. “The longest study examined both health and telomeres after one year — and we all know that cancer can take years and years to develop. So this is not sufficient to rule out the increased risk of certain types of cancers from telomerase activators,” she says. Aviv’s verdict on telomerase supplements is even harsher. “Nobody knows what they do. I would not take them,” he says.
For now, telomere biology is still in large part an enigma, chock-full of controversies and conflicting results. Studies measuring telomere lengths can have “tremendous scientific value”, says Epel, whereas individual telomere tests are a poor guide to your biological age. And, while too much telomerase may increase the risk of cancer, having shorter telomeres is linked with a range of other health problems. What is clear is that the length of our telomeres changes very little in adulthood. If we do want to nurture telomeres, the best time to do it is before birth and in early childhood, by limiting exposure to things like pollution, stress and certain chemicals. After that, the lifestyle advice is simple. A healthy diet and regular exercise will do you good – even if it doesn’t show up in your telomeres.
A better biological clock?
Wrinkles, greying hair, loss of muscle tone: the ravages of time on our bodies are obvious. But many people would like a more objective measure of how they are ageing. If the length of the telomeres on the end of our chromosomes isn’t the answer, there may be an alternative.
As we get older, our cells accumulate epigenetic changes — biochemical additions to the DNA that turn genes on or off without affecting the genetic sequence itself. How quickly this happens is influenced by our lifestyle. Things like diet, stress and whether you meditate can speed up or slow down the process, leaving visible marks in your DNA. What’s more, studies show that people with more of these epigenetic marks are at greater risk of premature death than those with fewer marks.
Some believe that this “epigenetic clock” is a better indicator of biological age than telomere length. But geneticist Steve Horvath at the University of California, Los Angeles, points out that the two approaches measure different aspects of ageing. Epigenetic clocks are stronger predictors of lifespan, he says, but telomere length provides information about the number of cell divisions that have occurred. He also worries that epigenetic clocks might fall victim to the kind of hype that now surrounds telomeres, with commercial labs offering oversimplified tests that can be easily misinterpreted. “It’s one of my worst fears,” he says.
