How We Age
In his book, “Lifespan,” celebrated scientist David Sinclair lays out exactly why we age—and why he thinks we don't have to.
Outside
- Graham Averill
The oldest-known living person is Kane Tanaka, a
Japanese woman who is a mind-boggling 116 years old. But if you ask David Sinclair,
he’d argue that 116 is just middle age. At least, he thinks it should
be. Sinclair is one of the leading scientists in the field of aging, and he believes that growing old isn’t a natural part of life—it’s a disease that needs a cure.
Sounds crazy, right? Sinclair, a Harvard professor who made Time’s list of the 100 most influential people in the world
in 2014, will acquiesce that everyone has to die at some point, but he
argues that we can double our life expectancy and live healthy, active
lives right up until the end.
His 2019 book, Lifespan: Why We Age and Why We Don’t Have To
($28, Atria Books), out this fall, details the cutting-edge science
that’s taking place in the field of longevity right now. The quick
takeaway from this not-so-quick read: scientists are tossing out
previous assumptions about aging, and they’ve discovered several tools
that you can employ right now to slow down, and in some cases, reverse
the clock.
In the nineties, as a postdoc in an MIT lab,
Sinclair caused a stir in the field when he discovered the mechanism
that leads to aging in yeast, which offered some insight into why humans
age. Using his work with yeast as a launching point, Sinclair and his
lab colleagues have focused on identifying the mechanism for aging in
humans and published a study in 2013 asserting that the malfunction of a
family of proteins called sirtuins is the single cause of aging.
Sirtuins are responsible for repairing DNA damage and controlling
overall cellular health by keeping cells on task. In other words,
sirtuins tell kidney cells to act like kidney cells. If they get
overwhelmed, cells start to misbehave, and we see the symptoms of aging,
like organ failure or wrinkles. All of the genetic info in our cells is
still there as we get older, but our body loses the ability to
interpret it. This is because our body starts to run low on NAD, a
molecule that activates the sirtuins: we have half as much NAD in our
body when we’re 50 as we do at 20. Without it, the sirtuins can’t do
their job, and the cells in our body forget what they’re supposed to be
doing.
Sinclair splits his time between the U.S. and
Australia, running labs at Harvard Medical School and at the University
of New South Wales. All of his research seeks to prove that aging is a
problem we can solve—and figure out how to stop. He argues that we can
slow down the aging process, and in some cases even reverse it, by
putting our body through “healthy stressors” that increase NAD levels
and promote sirtuin activity. The role of sirtuins in aging is now fairly well accepted, but the idea that we can reactivate them (and how best to do so) is still being worked out.
Getting cold, working out hard, and going hungry every once in a while
all engage what Sinclair calls our body’s survival circuit, wherein
sirtuins tell cells to boost their defenses in order to keep the
organism (you) alive. While Sinclair’s survival-circuit theory has yet
to be proven in a trial setting, there’s plenty of research to suggest
that exercise, cold exposure, and calorie reduction
all help slow down the side effects of aging and stave off diseases
associated with getting older. Fasting, in particular, has been well
supported by other research: in various studies, both mice and yeast
that were fed restricted diets live much longer than their well-fed
cohorts. A two-year-long human experiment
in the 1990s found that participants who had a restricted diet that
left them hungry often had decreased blood pressure, blood-sugar levels,
and cholesterol levels. Subsequent human studies found that decreasing calories by 12 percent slowed down biological aging based on changes in blood biomarkers.
Longevity science is a bit like the Wild West: the
rules aren’t quite established. The research is exciting, but human
clinical trials haven’t found anything definitive just yet. Throughout
the field, there’s an uncomfortable relationship between privately owned
companies, researchers, and even research institutes like Harvard:
Sinclair points to a biomarker test by a company called InsideTracker
as proof of his own reduced “biological age,” but he is also an
investor in that company. He is listed as an inventor on a patent held
by a NAD booster that’s on the market right now, too.
While the dust settles, the best advice for the curious to take from Lifespan
is to experiment with habits that are easy, free, and harmless—like
taking a brisk, cold walk and eating a lighter diet. With cold exposure,
Sinclair explains, moderation is the key. He believes that you can reap
benefits by simply taking a walk in the winter without a jacket. He
doesn’t prescribe an exact fasting regimen that works best, but he
doesn’t recommend anything extreme—simply missing a meal here and there,
like skipping breakfast and having a late lunch.
Lifespan is a timely book, but it’s not
necessarily an easy read. The science is dense, and even listening to
Sinclair explain it on podcasts and during presentations doesn’t help
cut through all of the nerd speak. But if you’re even mildly hopeful
about dunking a basketball at the age of 50, or hiking the Appalachian
Trail at 70, or blowing 100 candles out on your birthday cake someday,
you might consider making room for Lifespan on your bookshelf. There’s enough useful information to make it worth your time.
