The Science of Yoga

living . It turns out that several of the miracles—if false in terms of otherworldly feats—nonetheless reflect a real ability of yogis to accomplish lesser manipulations of the body that produce a range of health benefits. Take the heart. Bagchi may have shattered Yogananda’s claims about full stoppage. But decades of investigations have shown that yoga can produce heart repercussions that work powerfully on behalf of cardiovascular health, a potentially vital issue of civic welfare since heart disease is the leading cause of death in the industrialized world. The studies range from anecdotal to rigorous. But their large number—dozens conducted everywhere from India and Japan to Europe and the United States—argue persuasively that yoga works remarkably well. It has been found to lower such cardiovascular risk factors as high blood pressure, blood sugar, cholesterol, and levels of fibrinogen, a protein involved in blood clotting. It has also reduced signs of atherosclerosis—an underlying factor in heart disease that arises when cholesterol and other fatty deposits begin to clog the arteries. Finally, it has been found to raise levels of antioxidants in the bloodstream and to lower oxidative stress, a euphemism for highly reactive species of oxygen that wreak havoc with cellular machinery.
    More important, scientists have found that the lowered risk factors translate into medical benefits. Clinical studies have shown that patients who do yoga have fewer hospital visits, less need for drug therapy, and a smaller number of serious coronary events ranging from heart attacks to death. Analysts at the University of Virginia reviewed seventy of the studies and concluded in 2005 that yoga shows promise as a “safe and cost-effective intervention” for improving cardiovascular health.
    A different field of research shows that yoga can counteract the forces of aging—anotherarea rife with miraculous claims, as when the Hatha Yoga Pradipika spoke of eliminating wrinkles and gray hair.
    Consider a 2011 study. It looked at elderly women who took up yoga and found their balance much improved. That’s significant. For seniors, falls are the leading cause of death by injury.
    The spine is another target. Yoga has long claimed that all the bending and stretching will make the backbone youthful. Science has examined such declarations and found that yoga can, in fact, counteract the deterioration of the disks that lie between the vertebrae.
    The watery cushions act as pivot points and shock absorbers so that the vertebrae can move smoothly, letting the body go through its regular bending and rotating. The disks of adults have no blood supply of their own but instead rely on nearby vessels to nourish them. With normal aging, the already limited supply of blood diminishes still further and the disks gradually dry out and become thinner. As a result, the trunk shortens and a person shrinks in size. The thinning of the disks can result in a number of nerve conditions and severe pain.
    In 2011, the idea that yoga can slow such deterioration received support when physicians in Taiwan reported on a study of thirty-six people. Half had taught Hatha yoga for at least a decade, and the other half were judged to have exhibited good health. The two groups showed no statistical difference by age or sex. The physicians then scanned all the spines and carefully inspected the disks for signs of damage. The results, the team wrote, showed that the yoga teachers had “significantly less” degenerative disease than the control group.
    Why? The physicians suggested that spinal flexing may have caused more nutrients to diffuse into the disks. Another possibility, they wrote, was that the repeated tension and compression of the disks stimulated the production of growth factors that limited aging.
    The frontiers of biomedical science turn out to hold many clues to prospective health benefits. The new understandings reveal potential—if unproven—rewards for practitioners even if the word “yoga” never appears in the text or title of a scientific paper.
    One surprise centers on the vagus, often portrayed as the most important nerve in the body. It travels from the brainstem to the torso, where it radiates out tothe lungs, heart, stomach, liver, spleen, colon, and other parts of the abdomen. The word vagus shares etymological roots with “vagrant” and “vagabond,” denoting how it wanders through the body.
    The nerve’s action is