Vitamin D levels a factor in healthy lung function
A report published in the December 2005 issue of the journal Chest, the journal of the American College of Chest Physicians, revealed that higher levels of vitamin D are correlated with improved lung function compared to individuals whose levels of the vitamin are lower.
Peter N Black, MB ChB, and Robert Scragg, MB BS, PhD from the University of Auckland in New Zealand used data obtained in the Third National Health and Nutrition Examination Survey (NHANES III), which was conducted in the Untied States from 1988 to 1994. The current analysis involved 14,091 men and women aged 20 and older whose serum 25-hydroxyvitamin D levels were measured and who had undergone spirometry to assess lung function.
The duo found that participants whose vitamin D levels were in the top one-fifth of participants had a higher mean FEV1 (forced expiratory volume in the first second) and FVC (forced vital capacity) compared with those whose levels were in the lowest fifth. (FEV1 and FVC are measures which are used to evaluate lung function.) After adjustment for vitamin D supplement intake and other factors, the difference between the top fifth and the lowest fifth of vitamin D levels was 106 milliliters for FEV1 and 142 milliliters for FVC.
"Low levels of vitamin D have been associated with osteoporosis, hypertension, diabetes, and cancer," stated Dr Black, who was the study’s lead author. "Our research shows that vitamin D may also have a strong influence on lung health, with greater levels of vitamin D associated with greater and more positive effects on lung function.
“The difference in lung function between the highest and lowest quintiles of vitamin D is substantial and greater than the difference between former and nonsmokers,” he noted.
In an accompanying editorial, Rosalind Wright, MD, MPH, of Harvard Medical School’s Channing Laboratory commented, "Vitamin D would be a relatively simple, low-cost intervention that would likely have high compliance to prevent or slow loss of lung function in susceptible subgroups. However, further studies examining the relationship between vitamin D and lung function are warranted to identify who may benefit from such an intervention.”
A report published in the December 8 2005 issue of the Journal of Clinical Investigation revealed that supplementing with vitamin D3 could help improve the response of asthma patients to steroid drugs, which are commonly prescribed for the disease. When inhalable steroids fail to elicit a response, oral steroid tablets are the only way to control the disease, however the drugs have significant side effects and do not always result in improvement, even at higher doses.
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. About 11% of the population of the United States has COPD, with the disease becoming increasingly common among older women. According to the Mayo Clinic, COPD kills 85,000 people a year in the United States.
Epidemiologic studies have shown the severity of COPD correlates with low vitamin A intake. Other reports indicate that serum levels of vitamin A (retinol) are below normal in patients with COPD. In emphysema, the alveoli and bronchiole tubes of the lungs are destroyed, and the lungs become enlarged and less efficient. Although treatments exist, such as antibiotics and inhalers, none of these are curative. The vitamin A derivatives work by actually helping the lung regrow in areas destroyed by the disease. Retinoids are able to do this by turning on the genes that signal the growth of lung tissue.
The relationship between vitamin A status and COPD was further explored in a two-part study by researchers at the Faculty of Medicine of Botucatu UNESP in Sao Paulo, Brazil (Pavia et al. 1996). In the first part of the study, 36 men, age 43-74 years, were divided into five groups: healthy nonsmokers, healthy smokers, smokers with mild COPD, former smokers with moderate-severe COPD, and former smokers with severe, complicated COPD. All subjects underwent pulmonary function testing, and dietary intake of vitamin A was estimated from a food-frequency questionnaire. In addition, serum levels of retinol and other vitamin A-related compounds were determined from fasting blood samples. The results of this part of the study showed that serum levels of vitamin A were significantly lower in the two groups with moderate or severe COPD, although no group exhibited overt vitamin A deficiency.
A dietary deficiency of vitamin D inhibits the production of the protein that binds calcium in the intestines, so that calcium cannot be absorbed, even if there is adequate intake. Deficiencies of vitamin D are often found in the elderly and in women who have low intake of milk and receive inadequate exposure to sunlight. Vitamin D is potent in minute quantities; one microgram of cholecalciferol has 40 IU of vitamin D activity.
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