Nitrate-rich foods may affect asthma test

12/10/05 A diet of nitrate-rich foods may affect the results of exhaled nitric oxide (eNO) testing, a common test for asthma. In a new study, Belgian researchers recorded the eNO scores for 42 nonsmoking, nonasthmatic, healthy patients before and .5, 2, 4, 12, 15, and 20 hours after the intake of a nitrate-rich meal.

Researchers found that after patients consumed the nitrate-rich meal, consisting of 100 grams of lettuce and 50 grams of radishes, patients' eNO increased by 60 percent 2 hours after the meal. Even after 15 hours, patients' eNO scores were 22 percent over baseline and returned to normal only after 20 hours.

The findings stress the importance of advising patients to avoid nitrate-rich foods at least 20 hours before a scheduled eNO test. The study appears in the October issue of CHEST, the peer-reviewed journal of the American College of Chest Physicians.

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