Harmony Books, 2010
Scientific Blogging's own Greg Critser has tackled the science and business of eternal youth in his latest book. It's an engaging and excellent read. Critser is a fine storyteller, mixing his discussion of science with the lively personalities of the people involved. The book covers the latest science behind aging, the people who have shaped their lifestyles around that science, and the businesses that are trying to capitalize prematurely on the science.
As I read it, there are two big lessons to be drawn from the story Greg tells: 1) People with a passionate dedication to a pet theory, especially one about health, will eagerly latch on to science, not as a way to test their ideas, but rather as a technically sophisticated way to reinforce strongly held beliefs that are immune to disconfirmation. 2) There is always someone out there ready to take advantage of such people, by using science as a gloss to sell products of dubious validity.
The first lesson is illustrated by the caloric restriction movement. Eating less has long been seen as a way to live healthier, and to a degree, that is certainly true. As Critser relates, caloric restriction has often played a role in the scientific quest to combat aging, from the researches of a 15th century Venetian gentleman, all the way to high-tech 21st century model organism genetics. But modern-day caloric restriction has pushed the idea of eating less to an extreme, because such an extreme reduction in calorie intake does improve the lifespan of just about every laboratory organism, including yeast, worms, flies, and mice. The recent research behind caloric restriction in model organisms has been amazingly revealing - from a basic science perspective. When it comes to actual human health, the results are less sure.
We know that aging is controlled in part by genetics. As a leading researcher in the field, Cynthia Kenyon puts it:
It seemed to me that there was a good chance that the aging process, like so much else in biology, was not just a random and haphazard process but instead was subject to regulation by the genes. After all, rats live three years and squirrels can live for twenty-five, and these animals are different because of their genes. Also, most biological processes are subject to tight control by the genes.
Squirrels live longer than rats, who live longer than mice, even though all of these animals are similar. Our natural life span is significantly longer than chimps, whose physiology is very similar to ours. Aging isn't just a process of gradual deterioration; there is a strong reason to believe it is controlled by genes.
What makes the recent research in caloric restriction so interesting is that some scientists believe we have found some of those genes. Severely restricting calorie intake extends the lifespan of organisms from yeast to mice, and this appears to work through a fundamental cellular regulatory process, one that has been around in at least some form for about a billion years.
Typically it is good to be cautious when extrapolating from mouse studies to human health, but in this case there is a very strong reason to believe that these studies are quite relevant to human biology, because humans are not biologically exceptional. If some fundamental process is conserved from yeast to mice, you can bet the farm that this process is also operating in humans to some degree. (I'm placing bets, but it's critical to note that there is no direct evidence for lifespan extension by calorie restriction in humans, at least not at the level of confidence that we have in the mouse studies.)
There is a catch here, which Greg details in his book. The level of calorie restriction needed to see a significant lifespan extension in model organisms is severe. Mice and rats live only a few years, but humans typically live almost a century, and there side effects to this extremely spartan dietary regimen that crop up in humans, but not in mice. And, while humans and mice are similar, there are significant differences in our physiology, enough so that you should think twice before jumping into CR whole hog. Greg describes some of the effects experienced by the human caloric restriction (CR) practitioners he met - a lack of energy, a reduced sex drive, and, in the case of one twenty-something woman, a lack of menstrual cycles. That's just not healthy. (I recently has a conversation with my physician who has seen the same thing in a group of people who, while researching the effects of CR in dogs, have decided to also experiment on themselves. Some of them don't exercise because that would require eating more calories.)
What worries me most about this story is the treatment science gets by true believers in CR. As Greg describes them, they are technically well versed in the latest CR studies, and ready to confidently argue the case for CR with anyone who challenges them. And yet these people are actually profoundly anti-scientific. Their issue is one of temperament: scientific thinking isn't primarily a method to obtain and master facts; it's a way of making discoveries about the empirical world by minimizing self-deception, by learning the ways to avoid fooling yourself as you formulate hypotheses, perform experiments, or read about the experiments performed by others. The story of CR that Critser relates is largely a story of people who have already made up their minds; they're just waiting for the science to catch up.
It can be hard to be patient when it's your health that's at stake, but it takes time before science can offer even high confidence, not to metnion certainty.
Originally, this was going to be a brief review, but I'm having too much fun with this book. Brevity is no longer an option, so stay tuned for part 2.
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