Why can't we live forever? Some animals do, and I don't mean some 200 year old whale-I'm talking immortal. There are actually species of animals that don't age and could technically go on living forever-and why not? In a sense, humans are immortal in that a few of our cells live on as sperm or egg cells lucky enough to find each other. Each of our kids grow out of one of our cells, and that alone (the fact that a single cell can grow into an entire person!) should make, in comparison, the notion of keeping our bodies going indefinitely seem trivial.
Human longevity is certainly a hot research topic. Much of the research has focused on the role of DHEA (dehydroepiandrosterone), the most abundant steroid hormone in the human body. DHEA may help counteract the effects of stress, preserve female fertility, and it appears to be a strong predictor of longevity. Caloric restriction is thought to extend the lifespan of many animals by upregulating DHEA, which normally declines as we age. DHEA is sold as a "fountain of youth" over-the-counter dietary supplement, but concerns have been raised about safety, side effects, and quality control. There is, however, a natural way to boost DHEA levels.
As I note in my 3-min. video The Benefits of Caloric Restriction Without The Actual Restricting, after just 5 days on an egg-free vegetarian diet blood levels of DHEA rise about 20%. Upon further testing, it seems that the bodies of those eating vegetarian weren't necessarily producing more of it, but just losing less, something one normally only sees in fasting. Thus, by eating vegetarian one may be able to mimic the effects of caloric restriction, but without walking around starving all the time. For more on diet and life expectancy see Research Into Reversing Aging and Harvard's Meat and Mortality Studies plus my 30 other videos on lifespan. If you haven't yet, you can subscribe to my videos for free by clicking here.
Recently, the risk factors for mortality were published for the Harvard Nurse's Health Study, which is currently the most definitive long-term study ever on older women's health. It is the subject of my 2-min. video What Women Should Eat to Live Longer. Since the leading cause of death was heart disease, it is no surprise that dietary cholesterol consumption was significant risk factor for death. The second leading cause was smoking-related cancer deaths. Comparing the two, consuming the amount of cholesterol found in just a single egg a day appears to cut a woman's life short as much as smoking 5 cigarettes a day for 15 years.
The most protective behavior they found was fiber consumption. Eating just a cup of oatmeal's worth of fiber a day appears to extend a woman's life as much as 4 hours of jogging a week--though there's no reason we can't do both!
The one specific food most tied to longevity was nuts. Women appear to get 4 hours of weekly jogging benefit eating just two handfuls of nuts a week as well. Taking a step back, though, it's worth noting that the intake of cholesterol, only found in animal foods, was associated with living a shorter life and the intake of fiber, only found in plant foods, was associated with living a longer life.
A similar comparison has been made between the risk of smoking and eating processed meat (see Prevention Is Better Than Cured Meat). Though healthy eating can help mediate the devastating effects of smoking (see Smoking Versus Kale Juice, Preventing COPD With Diet, and Treating COPD With Diet), if you do smoke, please ask your doctor for help quitting. As a physician I've just seen too many good people die really horrible deaths from cigarettes.
-Michael Greger, M.D.
Image credit: Sister72/Flickr