People with nasal allergies or asthma may want to add broccoli sprouts to their diets, if early research findings pan out.

In a study of 65 healthy volunteers, researchers found that an oral preparation made from broccoli sprouts trigger an increase in inflammation-fighting enzymes in the upper airways.

The credit appears to go to a compound called sulforaphane, which is found naturally in broccoli and other cruciferous vegetables like Brussels sprouts, cauliflower and cabbage.

Sulforaphane triggers an increase in antioxidant enzymes that help counter cell damage and inflammation brought on by oxidative stress — from sources like air pollution and environmental allergens.

"Based on this study, compounds in broccoli sprouts have a very potent effect in boosting the airway's self-defense system against oxidative stress," explained lead researcher Dr. Marc A. Riedl, an assistant professor at the University of California Los Angeles David Geffen School of Medicine.

Whether broccoli sprouts can actually alleviate allergy and asthma symptoms is not yet known, Riedl told Reuters Health.

"Further studies will be needed to investigate the clinical significance, and so it's too early to give advice on a beneficial 'dose' of cruciferous vegetables," he said.

He noted, however, that broccoli sprouts contain 20 to 50 times the concentration of sulforaphane that mature broccoli does. So a person would have to eat large amounts of broccoli to get the sulforaphane dose that young broccoli sprouts provide.

The study, published in the journal Clinical Immunology, included 65 healthy men and women who were given various doses of the broccoli sprout preparation or a "placebo" made from alfalfa sprouts over three days.

The researchers took samples of the volunteers' nasal fluids to measure the activity of so-called Phase II enzymes, which control oxidative stress. They found that the broccoli sprout preparation sparked an increase in the protective enzymes, whereas the alfalfa-derived placebo did not.

The findings, Riedl said, show that "induction of protective enzymes can be accomplished using well-tolerated, readily available food sources."

This diet-based approach, he said, "may add another weapon to our fight against the increasing health burden of allergy and asthma."