Australian researchers have presented evidence of a causal relationship between vitamin D status and lung function, for mice at least.
Recent studies have linked poor vitamin D status to reduced lung function and disease, however until now causal data to confirm such a relationship has been lacking. The new study, published in the American Journal of Respiratory and Critical Care Medicine, claims to offer the first evidence of linking low levels of vitamin D to a reduction in lung function and altered lung structure.
“For the first time, we have demonstrated a direct role for vitamin D in causing decreased lung function … confirming the assertion by epidemiological studies that there is a relationship between vitamin D deficiency and lung function,” said the study’s lead researcher Dr Graeme Zosky, from the Telethon Institute for Child Health Research in Australia.
“The differences we observed in lung volume and lung mechanics, which were substantial and physiologically relevant, raise serious concerns regarding the increased prevalence of vitamin D deficiency in communities around the world,” he said.
According to the authors, the active form of vitamin D – 1,25-dihydroxyvitamin D (1,25(OH)2D) – is critical in immune regulation, and deficiency of the vitamin has been linked to both autoimmune disease and cardiovascular disease.
They noted that various epidemiological studies have previously shown an association between low maternal vitamin D status and offspring wheeze; decreased serum vitamin D and asthma severity; and chronic obstructive pulmonary disease (COPD) severity and levels of serum vitamin D.
However, the authors also said that low serum vitamin D levels are generally associated to low physical inactivity levels, which is also known to play an important role in lung functioning.
“Given the known association between increased asthma and COPD severity and low physical activity levels, a causal link between vitamin D and these respiratory diseases has been difficult to establish,” said the authors.
The new study aimed to change that by investigating vitamin D status – and its effects on lung development and function – in a mouse model where vitamin D levels status was manipulated and physical activity levels were matched.
The researchers used the mouse model of vitamin D deficiency – that was designed to match the physiology of human deficiency – to evaluate the lung development of deficient mice; comparing them to control mice with normal vitamin D status in order to determine what, if any, effects deficiency has on the growth, structure, and function of the lungs.
“The aim of this study was to determine if vitamin D deficiency results in altered lung function and/or structure as a potential explanation for the association between vitamin D and chronic respiratory disease,” said Zosky.
Compared to the control mice, airway resistance was found to be significantly higher in vitamin D-deficient mice, whilst lung volume was observed to much lower in mice with low status, said the researchers.
Examinations of specific tissue responses showed that low status mice also had smaller lungs with reduced function.
“These functional and structural abnormalities provide a mechanism explaining the link between vitamin D deficiency and obstructive lung disease,” said Zosky and colleagues.
They added that the study clearly demonstrates that vitamin D deficiency causes a reduction in lung function, adding that the results have important implications for prevention of lung diseases in populations where vitamin D deficiencies are common.
“Future studies need to be conducted to determine whether vitamin D deficiency-induced alterations in lung growth increase the severity of obstructive lung disease and to identify susceptible populations whose use of dietary vitamin D supplementation could be used to improve lung health outcomes,” said Zosky
Source: American Journal of Respiratory and Critical Care Medicine
Published online ahead of print
“Vitamin D deficiency causes deficits in lung function and alters lung structure”
Authors: G.R. Zosky, L.J. Berry, J.G. Elliot, A.L. James, S. Gorman, P.H. Hart