Vitamin D levels are associated with respiratory function and health, research from Australia shows. The findings suggest an additional process could be driving diseases such as chronic obstructive respiratory disease (COPD).
The study, “Vitamin D and respiratory health in the Busselton Healthy Ageing Study,” was published in the journal Respirology.
Vitamin D is well-known for its importance in regulating the amount of calcium and phosphate in the body, thereby maintaining healthy bones, teeth, and muscles.
Abnormal levels of the vitamin have been associated with respiratory illness and reduced lung function. Immune modulation and effects on lung structure are among the proposed mechanisms underlying these effects. However, more information is needed to better understand this relationship, especially regarding the role of diverse confounding factors.
Research shows that a vitamin D deficiency is prevalent among COPD patients, but no evidence of a link with lung function decline or mortality has been found.
Therefore, researchers determined the serum vitamin D levels in 5,106 people of baby-boomer age at the Australian Busselton Healthy Ageing Study to study their association with respiratory symptoms, disease, and lung function. A subset of 4,212 also had spirometry (lung function) data, while 2,669 underwent an overnight sleep study.
Respiratory symptoms were assessed by questionnaire and included wheeze (a whistling sound in the respiratory airways when breathing), shortness of breath, chest tightness, cough, and sputum.
Results showed that low levels of vitamin D correlated with respiratory illnesses such as bronchitis and asthma, and symptoms including wheezing and chest tightness.
In addition, poor lung function – as measured by forced vital capacity, or the total amount of air exhaled after a deep breath – was also associated with low levels of the vitamin.
Further indicating its key role in maintaining respiratory health, high levels of vitamin D were linked to better lung function, even after accounting for factors known to influence its levels, such as obesity, seasonal fluctuation, and other chronic diseases.
“The findings in this study coupled with recent studies investigating asthma outcomes and use of vitamin D supplements strengthen the proposed mechanistic relationship between vitamin D deficiency and respiratory disease,” the researchers wrote.
“There is emerging evidence that increasing levels [of the vitamin] either through lifestyle or supplementation can reduce asthma symptoms and severity among individuals with inadequate levels,” Siobhain Mulrennan, MD, the study’s first author, said in a press release.
Women under the age of 55 showed the highest prevalence of blood vitamin D deficiency (less than 50 nmol/L). The overall prevalence was 8.0 percent. Approximately 11% of respondents were taking vitamin supplements.
Debate is still ongoing as to whether a deficiency of the vitamin contributes to COPD, asthma, or bronchitis, or if the low vitamin levels result from disease or its treatment.
“A follow-up study of these same study participants is currently underway which will allow us to investigate longitudinally the effects of vitamin D levels and its relationship to the development of respiratory illness and associated symptoms, as well as other health outcomes associated with ageing,” said Michael Hunter, MD, one of the study’s co-authors.
Furthermore, the data and DNA samples collected from the study’s cohort will be used to assess “the genetic factors that influence vitamin D levels and the relationship to lung function and common respiratory conditions such as asthma, [COPD] and bronchitis,” said Alan James, MD, the study’s senior author.