Ascorbic acid (vitamin C) supplementation protected against exercise-induced airway narrowing in this small group of people with asthma.

The study design makes this research noteworthy.

First, the details.

• 8 people with asthma and documented exercise-induced bronchospasm (EIB) were studied.
• They continued their usual diet.
• Each person received each treatment in this crossover design: 2 weeks of ascorbic acid supplementation (1500 mg/day) or placebo in random order.

And, the results .

• Ascorbic acid significantly reduced the maximum fall in post-exercise FEV1.
• FEV1 (forced expiratory volume at 1 second) is a measure of the maximum volume of air breathed out in 1 second.
• Asthma symptoms scores significantly improved.
• Other measures of airway inflammation and the allergic response also significantly improved with the ascorbic acid compared to the placebo and usual diet.

It’s a small study. But the fact that each person received each treatment advances our understanding of vitamin C and lung reactivity to exercise in asthmatic patients.

These results are supported by earlier research in this field.

1982

• In 12 asthmatic patients, pretreatment with ascorbic acid 500 mg led to a significant attenuation in bronchospasm 5 minutes after exercise compared to placebo.
• The results suggested a mild antibronchospastic action of ascorbic acid in subjects with EIB.

1997

• In 10 asthmatic patients who had stopped taking their asthma medicine, administration of ascorbic acid 2 grams showed no effect on lung function.
• However, 9 patients showed a protective effect on exercise-induced hyper-reactive airways
• And 4 of 5 taking ascorbic acid 500 mg/day for 2 more weeks maintained the protective effect.

The bottom line?
Everybody says more research is needed. But as it now stands, taking 500 to 1500 mg of vitamin C each day might help protect against exercise-induced airway narrowing in people with asthma.

7/4/07 13:00 JR