Researchers at UCLA have discovered that sulforaphane, a chemical in broccoli, triggers an increase of antioxidant enzymes in the human airway that offers protection against the onslaught of free radicals that we breathe in every day in polluted air, pollen, diesel exhaust and tobacco smoke. (A supercharged form of oxygen, free radicals can cause oxidative tissue damage, which leads to inflammation and respiratory conditions like asthma.)

This is one of the first studies showing that broccoli sprouts – a readily available food source – stimulated a two- to three-fold increase in antioxidant enzymes in the nasal airway cells of study participants who had eaten them, said Dr Marc Riedl, of the David Geffen School of Medicine at UCLA, the study's principal investigator.

The UCLA team worked with 65 volunteers who were given varying oral doses of either broccoli or alfalfa sprout preparations for three days. Broccoli sprouts are the richest natural source of sulforaphane; the alfalfa sprouts, which do not contain the compound, served as a placebo.

Rinses of nasal passages were collected at the beginning and end of the study to assess the gene expression of antioxidant enzymes in cells of the upper airways. Researchers found significant increases of antioxidant enzymes at broccoli sprout doses of 100 grams and higher, compared with the placebo group. The maximum broccoli sprout dosage of 200 grams generated a 101% increase of an antioxidant enzyme called GSTP1 and a 199% increase of another key enzyme called NQO1.

‘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’, Riedl said.

No serious side effects occurred in study participants receiving broccoli sprouts.

Journal Clinical Immunology - March 09

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First Published May 2009

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