20 February 2021 | New Scientist | 49type 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. ❚making it difficult to compare results 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.”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
developing nine out of 22 types of cancers,
including melanoma, ovarian and testicular
cancer. The effect is particularly strong for
some types of cancer, especially glioma, aA 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 (see main story), 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.
Marta Zaraska is a writer based in
Vexin, France, and author of Growing
Young: How friendship, optimism and
kindness can help you live to 100