Scientists claim they have evidence that explains why lifestyle changes known to be good for you — low-fat diets, exercise, reducing stress — can lengthen your life.
Based on a small, exploratory study, researchers say these good habits work by preventing chromosomes in our cells from unraveling. Basically, they assert that healthy living can reverse the effects of aging at a genetic level.
It's all about the little caps on our chromosomes called telomeres. They work like the plastic tips of shoelaces to protect the ends of chromosomes, the strings of genes in the heart of every cell that tell it what to do. Without telomeres, our cells would lose the ability to divide and would quickly die off.
Scientists have been fascinated by telomeres for several decades. In 2009, Elizabeth Blackburn, an author of the new study, shared a Nobel Prize for pioneering work in the field.
As people and other animals age, their telomeres get shorter and shorter — a well-grounded observation that some scientists think is not only a marker of aging but a fundamental driver of senescence.
Study author Dean Ornish of the University of California, San Francisco notes that things that are bad for us accelerate the shortening of telomeres.
"Smoking makes your telomeres shorter, and emotional stress is associated with shorter telomeres, and lack of exercise," Ornish says. "And we know that shorter telomeres are associated with an increased risk of many chronic diseases and a shorter lifespan."
Ornish is known for his work showing that heart disease, in particular, can be not only prevented but reversed by rigorous changes in diet, exercise and stress reduction.
In recent years he and his colleagues have focused on the hypothesis that telomeres are at the root of these health-promoting changes. They studied two groups of older men. One group didn't do anything special; the other adopted Ornish's healthy regimen.
"These included a whole foods, low-fat, plant-based diet that's also low in refined carbohydrates," Ornish says. "Walking for a half an hour a day. Doing various stress management techniques, including yoga and meditation, for an hour a day. And spending more time with their loved ones, including friends and family."
After five years, study authors say men who followed this regimen actually lengthened their telomeres by about 10 percent. Men who didn't had a 3 percent shortening of their telomeres over that period.
The big caveat is that this was a small study — only 10 men in the better-lifestyle group and 25 in the status quo group.
Moreover, 3 of the 10 in the healthy-living group actually had telomere shortening, while 8 of the 25 others had telomere lengthening. Ornish says that's apparently because some men assigned to the group for improved lifestyles didn't follow it as well, while some in the comparison group actually did adopt healthier habits.
Ornish says the research team expected that men with better habits and longer telomeres would also have higher levels of an enzyme called telomerase that maintains telomeres. But curiously, they didn't.
Despite this puzzle, the small numbers of men involved, and what researchers would call the "crossovers" between the two groups in their behaviors, Ornish says the results are statistically significant and consistent. He believes the findings are real and their implications profound.
"If your telomeres get longer, then your life is probably going to get longer, and you're going to have a lower risk of developing a wide variety of conditions," Ornish says. "And since it's the same lifestyle intervention that we've found could actually not only prevent but even reverse the most common chronic diseases, like heart disease, early-stage prostate cancer, Type 2 diabetes, etc., it makes sense."
Others in aging research are intrigued, but it's going to take some convincing.
"Certainly everyone in our field will agree that telomere length is telling us something," says Dr. Nir Barzilai of Albert Einstein College of Medicine in New York City.
But it's still not clear what telomere length — or lengthening — means, Barzilai says. And the new study doesn't answer that either.
"At the end of the day, this hasn't stopped any argument," Barzilai says. "Either you're healthy, so you have longer telomeres, or you have longer telomeres and that's why you're healthy. You can pick and choose what you believe in, and make an argument."
For instance, Barzilai has shown that centenarians have longer telomeres than 85-year-olds. But he thinks the centenarians' telomeres are longer because they're healthier, not the other way around.
But Dr. Nan-Ping Weng of the National Institute on Aging finds the new study "intriguing." He studies the effects of telomere shortening on immune cells.
"Can we demonstrate that cells with shorter telomeres have weaker immune function? The answer from our data is yes," Weng says. "But I don't believe the telomere is the only parameter that determines aging. There are many other things."
Apart from scientists' fundamental disagreement about the role of telomere shortening (or lengthening), there's something else that troubles many of them.
It's not only healthy cells that have longer telomeres. So do cancer cells. In fact, that may be what keeps them dividing out of control. So some researchers worry that interventions that lengthen telomeres — not healthful diet and exercise, necessarily, but perhaps a drug with that effect — could promote cancer.
"My sense is that the cancer problem is a really, really big problem," says Aubrey de Grey of the SENS Research Foundation in California, which funds aging studies. "The implicit hope is that cancer either will not be stimulated in the manner that many people think it will. Or else, even if it is, that we'll find ways to get around cancer somehow."
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