Vitamin D could play a role in keeping the lungs healthy, research suggests.
Vitamin D is essential for the processing of calcium
Patients with higher vitamin D levels in their blood had significantly better lung function, a University of Auckland team found in a study of 14,091 people.
The difference between the two was more marked than that between smokers and those who had quit, the study published in the journal Chest said.
Dietary supplements could boost lung function, the team suggested, but they added that more research was needed.
"Low levels of vitamin D have been associated with osteoporosis, hypertension, diabetes, and cancer," said lead researcher Dr Peter Black.
"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."
Dr Black said the difference in performance between those with the highest and lowest concentrations of vitamin D was more marked that the difference between non-smokers and those who had given up.
The team found that those people with the highest concentration of vitamin D in their blood significantly outperformed others in tests to measure their lung function.
However, he said: "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."
The tests included:
- The FEV1 test which measures the volume of air that can be forced in one second after taking a deep breath.
- The FVC test which measures the total volume of air that is expelled after taking a deep breath
The researchers found vitamin D was higher in men than women, was inversely related to obesity levels, and declined with age.
It was also lower in participants smoking more than 20 cigarettes a day compared with non-smokers.
Dr Peter Black said he was not sure why vitamin D has this effect on lung function.
But he suggested it may be because vitamin D affects the repair and remodelling of lung tissue, which goes on throughout life.
"The effects of vitamin D are not limited to bone and there is evidence that it can affect the growth of a wide variety of cell types."
Dr Mark Britton, a spokesman for the British Lung Foundation, told the BBC News website that it was likely that vitamin D had an impact on the development of the rib cage, rather than the lung tissue itself.
He said that failure to develop strong bones could impact on the size of the lungs.
Dr Michael Alberts, president of the American College of Chest Physicians, said: "Chronic lung conditions compromise quality of life for millions of people around the world.
"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."
Vitamin D is essential for the processing of calcium.
Unlike other vitamins, it can be made in our bodies as a result of exposure to sunlight, providing the necessary starting materials are there to start with.
It is also contained in a few foods including oily fish, fish oils, butter and eggs.