ANTIOXIDANTS IMPROVE PULMONARY FUNCTION

BUFFALO—Increasing evidence suggests that oxidants play a role in lung injury and that dietary antioxidants may protect against oxidative damage. A recent study, for instance, shows a strong correlation between serum antioxidant levels, particularly of ß-cryptoxanthin and vitamin E, and pulmonary function.[1]

“There is accumulating evidence that antioxidant vitamin status is positively related to lung function,” Holger J. Schünemann, MD, PhD, told RESPIRATORY REVIEWS. “Earlier research had shown that vitamin E depends on the presence of vitamin C, but more recent studies have suggested that vitamin E may act independently. Our study lends some support to this observation,” said Dr. Schünemann, an Assistant Professor of Medicine and Social and Preventive Medicine at the State University of New York, Buffalo.

To better understand the relationship of dietary antioxidant levels to respiratory health in the general population, Dr. Schünemann and colleagues investigated the association between standard measurements of pulmonary function (forced expiratory volume in one second [FEV1] and forced vital capacity [FVC], both measured as a percentage predicted) and serum levels of vitamins C and E, retinol, and carotenoids (ß-cryptoxanthin, ß-carotene, lycopene, and lutein/zeaxanthin). Subjects included 1,616 randomly selected residents of Western New York who were 35 to 79 years old and did not have respiratory disease.

After adjusting for demographic data, such as age and smoking history, the researchers found a direct relationship between serum antioxidant levels and pulmonary function. Participants with the lowest levels of serum antioxidants had consistently lower FEV1% and FVC% than did those with higher serum levels. Furthermore, pulmonary function rose as levels of most serum antioxidants rose.

When all of the antioxidants were analyzed together, ß-cryptoxanthin and vitamin E were found to have the strongest association with FEV1% and FVC%. The association between vitamin E and respiratory health was not dependent on vitamin C levels. Furthermore, retinol had an independent effect on FEV1%, and lutein/zeaxanthin on FVC%.

CAUSE OR COINCIDENCE?

“Our findings suggest a beneficial effect of measured antioxidants on pulmonary function. However, although we attempted to control for factors such as socioeconomic status, we cannot exclude [the possibility] that other healthy lifestyle factors, such as a healthy diet, may play a role,” noted Dr. Schünemann. “We need longitudinal and randomized controlled trials. In addition, we need to explore other substances with antioxidant properties, such as flavonoids and potent antioxidants, as therapeutic agents. There is uncertainty about whether we can recommend antioxidant supplements, but there is increasing evidence for a potential role of low-dose vitamin C and E supplementation in those who do not have contraindications.”

—Deborah L. O’Connor