For the first part of this conversation, see Live Long and Prosper: A Conversation About Aging with Cynthia Kenyon.
For someone who has become the darling of anti-aging research advocates, UCSF's Cynthia Kenyon, PhD, is remarkably conservative about her personal dietary regimen. "I eat a low-carb diet because we've shown that keeping insulin levels low is good for animals, and we're animals."
Kenyon also exercises moderately, drinks a glass or two of red wine every day, sips green tea and ingests a baby aspirin daily. "[The baby aspirin] is good for heart attacks and maybe cancer," says the 52-year-old director of the Larry L. Hillblom Center for the Biology of Aging. She also recommends staying out of direct sunlight to offset the appearance of aging.
None of these measures triggers immortality, of course. But even a cursory review of longevity and diet websites suggests that hucksterism and self-deception remain as timeless as ever. The most sinister notion now making its way through cyberspace is that food is an enemy, a curious flip side to the developed world's obesity epidemic, and one that allows adherents of extreme caloric restriction to mask near-anorexia as healthful living.
Like all responsible scientists who work close to the boundaries of popular culture, Kenyon worries that nuance gets lost in translation. "I think a high-carb diet (which gives you a lot of insulin) is not good for you," she explains. "But I don't think insulin and insulin growth factor are evil. We need them to grow and to process our food."
The key message here is balance. Kenyon's research has shown that if you go too far in genetically modifying the insulin pathway, the increase in life span stops. Knock out the gene entirely, and the animal dies. Intermediate steps, if not carefully calibrated, could — in theory, at least — trigger a disease. Kenyon is well aware of the pitfalls and, because she is, has not fallen prey to them.
"What's really interesting," Kenyon enthuses, "is that you can get the life span benefits by taking away the insulin receptor in individual tissues. So it might not be overall percentage of insulin function we need to concentrate on, but a selective percentage in different tissues — like fat cells, for example."
Is a pill to slow aging in the works, then? Not right away, although Kenyon's company, Elixir Pharmaceuticals, is developing drugs that target metabolic disease (and who knows, maybe aging as well) by reducing insulin levels and increasing the cell's sensitivity to insulin, something that goes awry in type 2 diabetes.
You would think that with all this talk and all this ink, Kenyon would rarely encounter skeptics anymore. But take it from her: She does all the time. "Some people say to me, 'Well, aging is a disease, isn't it, so you're really talking about treating a medical condition.' I think they're having fun with words because, by definition, a disease is something physical that happens to some, but not all."
Progeria, for example, is considered a disease because the rapid aging it causes does not affect everyone. If progeria or Alzheimer's happened to everyone, these conditions would not be called a disease. They would simply be considered "aging." Living to be 100 is another example. Are those who fail to reach triple digits "diseased" by comparison? How about not being able to run as fast when you're older? Is running more slowly a disease?
We don't bother calling these things a disease because they are part of an uneven process that we accept, if sometimes disregard or abhor. Perhaps that is why Kenyon constantly confronts pessimism. Pessimism is a natural defense against the kind of disappointments aging makes commonplace. "A lot of people still think that when you make worms live six times longer, it's a cocktail trick, something that's interesting and fun, but not a reality or a possibility."
Kenyon's response is characteristically rich, substantive and upbeat. There are good reasons why we now live as long as we do, she says. From a cultural perspective, improvements in public health, more and better drugs such as antibiotics, and the fruits of an organized society — to name just a few — offer protection, a food supply, opportunity and general well-being, whatever society's obvious shortcomings.
So it's not unreasonable, she says, for people to assume that we've reached our magical limit, which averages 75 years for American men born today, and 80 years for women — give or take the impact of genes, lifestyle and good fortune.
"But I don't see why that has to be our natural age limit," she continues. Think of it this way. "There are long- and short-lived insects, birds and mammals. During evolution, there must have been a first insect, a first bird, a first mammal, and probably all of them had a short life span." Evolution has shown that aging, well, is evolvable. "It's not like life span changed just once and that's it. It can happen again."
What happens if she's right and, like the worms in her lab, we learn how to stay youthful and fit well past 100, and then, sometime around 120 years old, crash and die quickly? Wouldn't society as we know it crash even sooner under the weight of a new gerontocracy?
"Society would adapt," Kenyon proclaims with typical enthusiasm. "We've already changed things. It used to be that very few people made it to age 70. Now most people do. The birthrate would also have to come down, and that is happening now too, although you wouldn't want it to come down too far because the world needs young people."
Plus, she adds, we're not talking about a civilization in which walkers replace sports cars as a symbol of youth. Instead, the rate of aging would slow, so that a 90-year-old would look and feel like a 50-year-old. And, Kenyon adds, who wouldn't love that kind of energy, experience and vitality pulsing through society?
Her smile fades for a moment. She becomes thoughtful. Maybe universities wouldn't like it, she offers upon reflection. "You couldn't get tenure at 35 and then stay on faculty for 100 years. That would never happen."
- UCSF Department of Biochemistry and Biophysics
- Wormworld (Kenyon Lab)
- Calorie restriction
- Calorie restriction
- Longevity Meme Website
- The fast supper (calorie restriction diet)
- New York Magazine, October 30, 2006
- Old worms, new aging genes
- Science News, August 2, 2003
- Genes that act downstream of DAF-16 to influence the lifespan of C. elegans
- Nature, July 17, 2003
- Ageing: A message from the gonads
- Nature, May 27, 1999
- In Methuselah's mould
- PLoS Biology, January 2004
- One for the ages: A prescription that may extend life
- New York Times, October 31, 2006
- Aging Drugs: Hardest test is still ahead
- New York Times, November 7, 2006