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- A hundred years ago,
people lived only about 49 years
on average. Today, it's more like 76
years. But in the future, it could
be much, much longer - double or
triple the average human life span as
we know it.
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- "It's fascinating - the
prospect of most people
having the ability to live to the age of 150 or
200," says actor Alan
Alda, who is host of the PBS series
Scientific American Frontiers. In a
segment called "Never Say
Die," airing next Tuesday at 8 p.m.
ET/PT (check local listings),
Alda interviews scientists who are discovering
the secrets of aging and
investigating ways to delay the inevitable.
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- "When I first heard we
were doing a show on that,
I said, 'I hope they're checking
facts,'" Alda says in a phone interview.
"It seemed
preposterous, yet these are real scientists doing this."
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- Among them is Roy
Walford, a researcher at UCLA. Alda
says Walford believes that "if
you eat less, you'll live longer -
so long as you make sure that what
you do eat has high nutritional value."
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- Walford says, "It's been
known since 1935 that if
you keep animals on a very low-calorie diet,
but one that is not deficient
in vitamins, you extend their maximum
life span and their average life
span."
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- In the 1960s, he found in lab
experiments that mice can
live to twice their normal age if their
caloric intake is reduced by half.
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- Experiments involving rhesus
monkeys have found that
those on a similarly restricted diet appear
healthier and younger than
those on a normal diet. It's too soon to
tell whether their lives will
be significantly longer.
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- Walford is on a
high-nutrient, low-calorie diet. In the
PBS program, he prepares a meal
for Alda that is healthier than Alda's
usual turkey sandwich with a
side of pretzels.
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- "That guy has a very particular angle on eating,"
Alda says. "When you think about it, it's probably better to be free
of disease than to eat a pretzel. You don't think of it when you're facing
a pretzel, but if you're following that plan, your goal is to be healthy
for a long time."
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- And that's the whole idea, he says. "That impressed
me a lot when I talked to those guys - I kept talking about longevity,
and they kept talking about health. Longevity is secondary. The real goal
is to stay healthy as long as possible."
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- At the University of California
at San Francisco, researcher
Cynthia Kenyon has, through chemical
mutation of genes, managed to breed
a race of nematodes - tiny worms -
that live twice as long as normal nematodes,
which have a two-week life
span.
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- The
mutant nematodes age, but more slowly. "In other
words," Alda
says, "everything takes twice as long - youth, middle
age and old
age. This really could happen with people someday."
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- Alda visits a Menlo
Park, Calif., biotech company called
Geron, where Cal Harley is using
genetic engineering to restore a cell's
telomeres - the protective tips
of a chromosome. The telomeres are compared
to the plastic tips on the
ends of shoelaces.
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- Normally, telomeres wear away with age, and when they
get to 5%
of their normal length, the cells stop dividing.
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- "They're like the clock of
life," Harley says.
By inserting the telomere-restoring gene into
tissue, Harley has created
cells that divide indefinitely.
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- "There is no
reason why, genetically, we can't have
a life span that could be 100,
200, 300 years," he says. "There
is no theoretical reason
that is impossible."
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- But don't count on it, advises Huber Warner, associate
director of the Biology of Aging program at the National Institute on
Aging.
Warner, who was not involved in the Scientific American
Frontiers program,
says that while it's true that genes play a role in
long life, environment
also is a factor.
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- "The maximum human life
span is at least 122 years.
We know that because somebody has lived
that long," he says. "But
the average life span for women is
about 80 in developed countries, and
for men it's 74 to 75, so clearly
there is something happening to promote
people to die before the
maximum life span."
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- Behavior - smoking cigarettes or eating too much or
failing
to exercise - can interact with a genetic predisposition to
spell disaster,
he says.
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- While research on aging is progressing, Warner doesn't
expect to see his 200th birthday. "I admit, if the maximum life span
of a human is 120, and with caloric restriction if you could increase it
40%, you could get close, but that hasn't even been proven in monkeys.
There is some evidence, but it's not remotely complete."
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- The nematode story is
"the most successful in terms
of extended life span," Warner
says, "but the nematode is a weird
organism compared to mammals. .
. . Extrapolating from a nematode to a
human is risky
business."
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- Nematode researcher Kenyon is more optimistic. "I
have a
retirement account, so that means that at some level I think I might
have to retire at some point," she tells Alda. "So part of me
is living in the real world."
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- Still, she says, she "may
not have to use it for
a long time. It could get really big!"
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