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Higher levels of vitamin D linked to better lung function

Vitamin D may play a role in keeping our lungs healthy, with greater concentrations of vitamin D resulting in greater lung health benefits. A study in the December issue of CHEST, the peer-reviewed journal of the American College of Chest Physicians (ACCP), shows that patients with higher concentrations of vitamin D had significantly better lung function, compared with patients with lower concentrations of vitamin D.

"Low levels of vitamin D have been associated with osteoporosis, hypertension, diabetes, and cancer," said lead author Peter Black, MB, ChB, Department of Medicine, University of Auckland, Auckland, New Zealand. "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."

Researchers from the University of Auckland examined the relationship between vitamin D and lung function using participants from the United States National Health and Nutrition Examination Survey (NHANES III) carried out during 1988 to 1994. The study included 14,091 people aged >= 20 years, who were interviewed at mobile examination centers, had spirometry performed, and had serum 25-hydroxyvitamin D measured.

Vitamin D measurements were divided into five groups (quintiles), ranging from more than 85.7 mL to less than 40.4 mL. After adjusting for gender, age, ethnicity, body mass index, and smoking status, the differences between the lowest quintile of vitamin D and the next quintile were 79 mL for FEV1 and 71 mL for FVC. In comparison, the differences between the highest and lowest quintiles of vitamin D were 126 mL for FEV1 and 172 mL for FVC.

With further adjustment for physical activity, intake of vitamin D supplements and milk, and antioxidant level, the difference between the highest and lowest quintiles of vitamin D also was significant at 106 mL for FEV1 and 142 mL for FVC. In addition, an association between vitamin D and FEV1 was seen in non-Hispanic whites and blacks and was greater for those over 60 years and current or former smokers.

"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," said Dr. Black. "Although there is a definite relationship between lung function and vitamin D, it is unclear if increases in vitamin D through supplements or dietary intake will actually improve lung function in patients with chronic respiratory diseases."

Overall, male gender, younger age, white ethnicity, nonsmoking status, and regular, vigorous physical activity were associated with the highest lung function. Vitamin D was higher in men than women, was inversely related to BMI, and declined with age. Vitamin D also was lower in non-Hispanic blacks and Mexican-Americans, compared with non-Hispanic whites, and it was lower in participants smoking more than 20 cigarettes a day compared with nonsmokers.

"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," said author of the study's corresponding editorial Rosalind Wright, MD, MPH, Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.

"Chronic lung conditions compromise quality of life for millions of people in the United States and around the world," said W. Michael Alberts, MD, FCCP, President of the American College of Chest Physicians. "By understanding the effect that vitamins have on lung function, we may be able to identify new and more effective treatments for these debilitating diseases."

CHEST is a peer-reviewed journal published by the ACCP. It is available online each month at www.chestjournal.org. The ACCP represents 16,500 members who provide clinical respiratory, sleep, critical care, and cardiothoracic patient care in the United States and throughout the world. The ACCP's mission is to promote the prevention and treatment of diseases of the chest through leadership, education, research, and communication. For more information about the ACCP, please visit the ACCP Web site at www.chestnet.org.