Free radicals have long been known to cause oxidative tissue damage -- and that can lead to inflammation and respiratory disorders such as COPD and asthma. The new study, just published in the March edition of the journal Clinical Immunology, documents that sulforaphane found in broccoli triggers an increase of antioxidant enzymes which protects the airways against free radicals that most people breathe daily every time they are in polluted air, pollen, diesel exhaust and tobacco smoke.
"A major advantage of sulforaphane is that it appears to increase a broad array of antioxidant enzymes, which may help the compound's effectiveness in blocking the harmful effects of air pollution," Dr. Marc Riedl, the study's principal investigator and an assistant professor of clinical immunology and allergy at the David Geffen School of Medicine at UCLA, said in a statement to the media.
Over a period of three days, the UCLA researchers gave 65 volunteers varying oral doses of either broccoli or alfalfa sprouts (which do not contain sulforaphane, so the alfalfa served as a control for the test). Nasal passages of the research subjects were rinsed at the beginning and end of the study to measure the gene expression of antioxidant enzymes in cells in the volunteers' upper airways. "We found a two to three-old increase in antioxidant enzymes in the nasal airway cells of study participants who had eaten a preparation of broccoli sprouts," Dr. Riedl explained in the media statement.
Overall, the scientists found significant increases of antioxidant enzymes in the group taking the broccoli sprout preparation at doses of 100 grams and higher. When the broccoli sprout dosage was increased to 200 grams, it resulted in an especially dramatic increase in airway protective enzymes -- a 101 percent increase of an antioxidant enzyme called GSTP1 and a 199-percent increase of another key enzyme called NQO1.
"This is one of the first studies showing that broccoli sprouts -- a readily available food source -- offered potent biologic effects in stimulating an antioxidant response in humans," Dr. Riedl stated in the press release. "This strategy may offer protection against inflammatory processes and could lead to potential treatments for a variety of respiratory conditions."
Although Dr. Riedl said it is too early to recommend a specific dosage of broccoli to protect the airways, he does recommend including broccoli and other cruciferous vegetables as part of a healthy diet.