Vitamin C may help ease exercise-induced breathing problems, according to a study conducted by researchers from the University of Helsinki, Finland, and published in the journal Allergy, Asthma & Clinical Immunology.
Some people, including many with asthma, suffer from bronchoconstriction or other forms of respiratory distress after exercising. Prior studies have suggested that this bronchoconstriction is mediated in part by histamines, prostaglandins and cysteinyl leukotrienes, all of which are metabolized through processes that rely on vitamin C. In addition, vitamin C is a potent antioxidant, and might therefore disrupt the oxidative pathways that have also been linked to exercise-induced respiratory distress.
Regular metabolic processes cause the release of oxidative compounds, also known as free radicals. These chemicals can then cause damage to cells and DNA. Free radical production accelerates during exercise.
Vitamin C improves breathing 50 percent or more
The researchers carried out an analysis of several prior studies. In three of those studies, vitamin C was found to reduce the post-exercise decline of FEV1 by 50 percent. FEV1, or forced expiratory volume, is the amount of air that you can force out of your lungs in one second.
Analyzing another five studies showed that respiratory symptoms decreased by 50 percent when people under short-term, heavy physical stress were given vitamin C. Yet another found that male adolescent competitive swimmers given vitamin C experienced a 50 percent decrease in the duration of exercise-induced respiratory symptoms.
Because FEV1 measures only the obstruction of large airways, the researchers also re-analyzed a prior study that looked at the effect of vitamin C on exercise-induced decline in FEF25-75 and FEF60, which measure small airway obstruction. Typically, FEF25-75 and FEF60 decrease twice as much as FEV1 in those with exercise-induced bronchoconstriction.
The study consisted of 12 people of average age 26 who suffered from asthma and from exercise-induced bronchoconstriction. Participants were given vitamin C or a placebo on separate days, and their FEV1 and FEF60 levels were measured both before and afterexercise. The data from the study had not previously been thoroughly analyzed.
Among participants who experienced a significant drop in FEF60 following exercise (5 of the 12), vitamin C increased post-exercise FEF60 levels by 50 to 150 percent.
“[G]iven the safety and low cost of vitamin C,” said researcher Harri Hemila, “and the consistency of positive findings in the nine randomized trials on vitamin C against exercise-induced bronchoconstriction and respiratory symptoms, it seems reasonable for physically active people to test whether vitamin C is beneficial on an individual basis, if they have documented exercise-induced bronchoconstriction or suffer from respiratory symptoms such as cough or sore throat after taking vigorous exercise.”
Also protects in lung disease
Prior research has also indicated that vitamin C may improve muscle function in people with chronic obstructive pulmonary disease (COPD). In COPD, lung function progressively worsens and the function of skeletal muscles degrades, making ordinary activities difficult or impossible.
The mechanisms of COPD-induced loss of fitness are unclear. Some suggested factors include inadequate oxygen to the muscles, loss of fitness due to inactivity, damage to cells’ metabolic processes and oxidative stress.
A study conducted by researchers from the George E. Whalen VA Medical Center and the University of Utah and published in the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology found that COPD patients given intravenous vitamin C experienced less muscle fatigue following knee flex exercises. In addition, patients’ breathing slowed and improved, the antioxidant activity in their blood increased, and their resting blood flow and blood pressure decreased.
The findings strengthen the evidence that oxidative stress plays a key role in COPD symptoms, including loss of muscle function.
“Targeting oxidative stress with some form of antioxidant therapy in a clinical setting may represent an important therapeutic avenue for patients with COPD,” the researchers wrote.