Q: I've been trying to learn more about the science of aging, but I find some of the concepts confusing. What is the difference between aging and senescence? Do scientists think humans have a maximum lifespan? Michele Korolewicz, Nashville, Tennessee
Leonard Guarente: Aging is a continuous process, while senescence refers to the inevitable end state. Analysis of human actuarial tables—statistics showing, among other things, the number of deaths at each age—suggests that maximum lifespan of humans is about 120 years. A goal of our research is to allow humans to live longer, healthier lives until they reach the end of their maximum lifespan.
Q: I want to start taking resveratrol in pill form. Is it available to the public yet? G. Diaz, Santa Fe, New Mexico
Guarente: Although there is no cure-all, FDA-approved anti-aging remedy on the market, you can find resveratrol in health food stores. As with all supplements, you should take no more than the recommended dosage, because there could be potential for damaging side effects that we do not know about yet.
Q: Researchers in [this segment] discuss how caloric restriction or the consumption of resveratrol could slow the onset of ailments associated with aging, such as diabetes or Alzheimer's disease. Is it possible that the effects of these diseases could be reversed if someone already afflicted with them begins cutting calories and the like? Douglas Luckett, Nashville, Tennessee
Guarente: We do not know for sure at this point in aging research. My guess is that the progression of the diseases would be slowed in people already afflicted, especially if the treatment were started early, but there is no evidence yet showing that the damage done by these diseases could be reversed.
Q: It seems counterintuitive that cutting food intake could help us live longer. How does this work? John S. Waterman, Oxford, Mississippi
Guarente: We think that animals can recognize food scarcity as a kind of stress and that they mount a physiological program to cope with the impending lack of nutrition. This program promotes health and longevity during these difficult times, and we believe that sirtuins are important agents that bring about the life-preserving effects of this diet. [Editor's note: See how calorie restriction and sirtuins affect aging in yeast].
Q: Since we need some calories to live, how many should the average person consume to remain healthy? Gordon Merseth, Portland, Oregon
Guarente: My advice is to find your ideal body weight, get there, and stay there. Roughly 2,000 calories per day is enough. Calorie restriction would involve much less, but I do not advise this because it makes for an unpleasant existence and can be harmful if not done carefully to provide adequate nutrition. Everyone is different, so what might work for me could be harmful to you. Your family doctor can help you figure out the best diet for you.
Q: What are the key daily items—e.g., foods or vitamins—that can be consumed to ensure a longer life? Is there a "formula" to follow to extend our healthy years? Dale Rice, Vancouver, Washington
Guarente: What I recommend is a healthy diet including fruit and vegetables (no saturated fats) and daily exercise. Having a positive attitude can also help. Consult your physician to find out what foods and activities might work best for you.
Q: Is there any compelling evidence showing that vegetarians or people who primarily consume seafood live longer than people who eat beef, pork, or chicken? Why is this? Peter Holmes, Seffner, Florida
Guarente: Not really. One interesting fact, however, is that people in Okinawa, Japan, seem to live long, and they eat primarily fish. Fish oil can be good for you, but animal fat is not. Stay away from trans fats and saturated fats, and if you choose to become vegetarian, be sure to find new sources for the proteins you would typically get from eating meat. Lentils are a good place to start.
Q: Statistics show that women tend to live longer lives than men. Why is this, and is there anything we men, specifically, can do to improve our odds? John S. Waterman, Oxford, Mississippi
Guarente: This is correct, but we do not know why. Hormonal differences may be just as important as lifestyle and diet when it comes to living longer. As for what men (or anyone) can do, I would refer you to my answer to Dale Rice above.
Q: I've always heard that aging results from chromosome damage—that after a certain number of divisions, as the ends of our cells' chromosomes wear away, our cells just can't divide anymore. But if that's the case, how is it that caloric restriction or drugs can slow aging? Kavan Negaran, Jacksonville, Florida
Guarente: There is no one cause of aging, including the one you mention. Calorie restriction triggers a physiological change that impacts and slows many cellular processes that must encompass all causes of aging, including chromosome damage.
Q: As scientific discoveries increase in their capacity to affect humanity, do scientists have an obligation to consider the consequences of their research, rather than pursuing knowledge for its own sake? Have you considered any negative consequences associated with the potential success of your aging research? Geoff Erickson, Boston, Massachusetts
Guarente: Yes. The important thing is that progress in our area will extend health span. Maximum lifespan might be slightly affected, but the big effect will be to keep people healthier longer. This has already been happening over the past century with better nutrition and healthcare, and ought to have beneficial effects on societies in the developed world.