High-Salt Diet Raises Asthma Risk

Exercise-induced attacks were more common, study found

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FRIDAY, June 17, 2005 (HealthDay News) -- Asthmatics prone to exercise-triggered attacks may want to cut back on salt in their diets, according to a new study.

The Indiana University research is the first to show that changing salt intake for just two weeks can alter airway inflammation, and the flow of oxygen into the bloodstream.

The study included 24 people with asthma and exercise-induced asthma. Some of the study volunteers were put on a low-salt diet of 1,446 milligrams of sodium per day for two weeks. Others were put on a high-salt diet of 9,873 milligrams of sodium per day, an amount that's typical for many American adults.

At the end of two weeks, the volunteers on the high-salt diet showed a dramatic decline in lung function after physical activity. Their forced expiratory volume in one second (FEV1) -- a standard measure of lung function -- taken 20 minutes after exercise dropped by 27.4 percent over the two weeks, compared with a 7.9 percent decline for those on the low-salt diet.

A decline of 10 percent or more in post-exercise FEV1 is considered abnormal.

"These findings show that modifying your diet has the potential to modify a disease state," study author and exercise physiologist Timothy Mickleborough said in a prepared statement.

High-salt diets have a number of physiological effects, including increased blood pressure and blood volume that can cause pulmonary swelling that, in turn, results in airway obstruction, Mickleborough explained.

The study volunteers on the high-salt diet also had higher levels of airway cells in their sputum. Airway cells have been linked to the development of asthma and EIA. The people on the high-salt diet also had more pro-inflammatory mediators, which can cause airway constriction.

The findings appear in the June issue of Medicine & Science in Sports & Exercise.

More information

The American Academy of Allergy, Asthma, and Immunology has more about exercise-induced asthma.

SOURCE: Indiana University, news release, June 8, 2005

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