Caffeine is chemically similar to theophylline, an older medication sometimes used to treat asthma.1 It has a mild effect on the airways, causing them to relax a little bit. Caffeine does not work well enough to replace asthma control medications or to treat an asthma attack. However, your health care provider may tell you not to have caffeine on the day of a lung function test, to be sure you get the most accurate results.2 Coffee, tea, cola drinks, and chocolate are the main sources of caffeine.
How does a normal amount of coffee affect lung function?
A recent study tested the effect of a “normal” amount of coffee.1 The study had 14 participants with mild to moderate asthma and good lung function. A normal amount is about two cups per day (16 ounces), which has about 200 mg of caffeine.3 Each participant drank 16 ounces of caffeinated coffee and 16 ounces of decaffeinated coffee on separate occasions. The results showed that a normal amount of caffeine did not improve lung function, reduce airway inflammation, or reduce airway sensitivity.
An older review paper came to a different conclusion. The authors of this paper looked at seven small trials to see how caffeine affects lung function.4 Their results showed that low doses of caffeine (5 mg per kg of body weight) can improve airway function for up to four hours.4 However, it is important to note that the purpose of this study was to see if people should avoid taking caffeine before lung function tests. It was not a study to see if caffeine can be used to treat asthma symptoms.4 The authors suggested that a much higher amount of caffeine might be needed to improve asthma symptoms. High levels of caffeine can cause symptoms such as shakiness, jitters, difficulty sleeping, headaches, dizziness, fast heart rate, and dehydration.5
Can caffeine prevent exercise-induced asthma?
One very small study was done to compare caffeine and albuterol for exercise-induced asthma symptoms.6 Ten athletes consumed a drink with different amounts of caffeine or no caffeine. They also used an inhaler with albuterol or fake treatment (placebo) before doing an exercise challenge. The researchers tested participants’ lung function before and after the exercise challenge. The results showed that moderate to high doses of caffeine (6 to 9 mg per kg of body weight) prevented the airways from narrowing during exercise.
However, these results are not enough to prove that caffeine prevents exercise-induced asthma. Caffeine is not one of the treatments recommended for exercise-induced asthma in guidelines from the American Thoracic Society.7 The main treatment for exercise-induced symptoms is albuterol and a ten-minute warm-up.
Can caffeine be harmful for people with asthma?
Caffeine should not be used in place of medications to treat worsening asthma symptoms. This can delay treatment and have serious consequences. High doses of caffeine can increase the side effects of theophylline.8 Avoid consuming large quantities of coffee, tea, cocoa, and chocolate if you are taking theophylline. Caffeine can make GERD (gastroesophageal reflux disease) worse, which may lead to more nighttime asthma symptoms.