Beta-carotene may protect against aging-associated decline in lung function
The April, 2006 issue of the journal Thorax published the finding of French researchers that having higher serum levels of the vitamin A precursor beta-carotene is associated with a reduction in the decline in lung power that occurs as we grow older.
The current study analyzed data from 535 men and women between the ages of 20 and 44 who participated in the European Community Respiratory Health Survey. Forced expiratory volume in one second (FEV1), which measures the volume of air forced from the lungs in one second following a deep inhalation and is used to evaluate lung function, and serum levels of vitamin A, vitamin E, and alpha and beta-carotene were assessed during the subjects’ initial examination in 1992 and at follow-up in 2000.
The average decline in FEV1 was 29.8 milliliters per year during the eight year period. While alpha-carotene, vitamin A and vitamin E levels were not associated with a reduction in the rate of FEV1 decline, beta-carotene levels were associated with a significantly slower rate. Men and women whose beta-carotene levels at the beginning of the study were in the top one-third of participants experienced a lower rate of decrease in FEV1 compared to those in the middle and lowest third, and for those whose beta-carotene levels increased between 1992 and 2000, the decline was also significantly reduced. Men had lower beta-carotene levels and a greater decline in lung function than women. Having low levels of vitamin E and beta-carotene combined with smoking was associated with the greatest decline in lung function, with individuals in this group experiencing twice the decline in FEV1 as that of the general young adult population.
The authors provide two possible explanations for their findings. One is that serum beta-carotene levels reflect levels of this antioxidant vitamin in the lungs, which helps to prevent free radical damage. They suggest that the lack of an effect associated with alpha-carotene in this study could be due to the low level of this carotenoid in lung tissue. A second explanation is that because beta-carotene and vitamin E scavenge the superoxide anion, a radical which has been shown to affect airway smooth muscle contractility and proliferation, the two nutrients may protect against excess of these functions.
“This is the first longitudinal study to show that beta-carotene and vitamin E may protect against accelerated decline in lung function, especially in heavy smokers,” the authors announce. “These powerful antioxidants may help to reduce oxidative stress—one of the factors thought to be involved in the pathogenesis of COPD—and thus may contribute to reducing the risk of morbidity and mortality related to this disease.”
Several lung diseases are collectively known as chronic obstructive pulmonary disease (COPD), including asthmatic bronchitis, chronic bronchitis (with normal airflow), chronic obstructive bronchitis, bullous disease, and emphysema.
One study measured antioxidant levels in smokers and in a group of chronic obstructive pulmonary disease patients. Smoking, acute COPD attacks, and asthma were all associated with very low blood serum levels of antioxidants and evidence of increased oxidative stress (Rahman et al. 1996). More studies have measured free-radical injury from pulmonary oxygen and the protective role of antioxidant enzymes. Results suggest that increased free-radical toxicity and decreased glutathione peroxidase and catalase activities in red blood cells play a role in COPD (Misso et al. 1996; Tekin et al. 2000).
There are many ways to diagnose emphysema, but the most accurate is the chest x-ray. Chest x-rays are also very useful in determining the amount of lung damage already sustained. Tapping on a patient's chest while listening with a stethoscope is a favorite technique of experienced doctors. Ruptured alveoli and overinflated lungs respond with a hollow sound. A registered respiratory therapist (RRT) can conduct a number of pulmonary function tests (PFTs). Spirometry measures the amount of air the patient can exhale in 1 second (forced expiratory volume, or FEV1) into a tube connected to the spirometer. The total amount of air the patient can exhale (forced vital capacity or FVC) is then compared to the FEV1 to determine the extent of airway obstruction.
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