Study leader Dr. Andre Nel of the David Geffen School of Medicine at the University of California, Los Angeles said that free radicals are byproducts of normal body processes, which can cause oxidative tissue damage, leading to disease such as the inflammation that causes clogged arteries. This oxidative damage to body tissues and organs is thought to be one of the major causes of aging.

"The mysteries of aging have always intrigued man," Nel said in a statement. "While we have known for some time that free radicals are important in aging, most of the past attention has focused on the mechanisms that produce free radicals rather than addressing the pathways used by the body to suppress their production."

Nel said that the defense of the body against oxidative stress damage may determine at what rate people age.

The study, published in the Journal of Allergy and Clinical Immunology, shows that a chemical present in broccoli -- sulforaphan -- is capable of stimulating a wide range of antioxidant defense pathways and may be able to interfere with the age-related decline in immune function.