June 19 (UPI) -- Lower than normal levels of vitamin D in the blood were linked to increased risk of early interstitial lung disease, according to an analysis of a new study.
Researchers at Johns Hopkins University studied medical information from 6,302 adults on average 62 years old with the rare disease that leads to disabling and irreversible lung damage characterized by lung scarring and inflammation. Their findings were published Tuesday in the Journal of Nutrition.
"Our study suggests that adequate levels of vitamin D may be important for lung health," Dr. Erin Michos, associate professor of medicine at the Hopkins School of Medicine, said in a press release. "We might now consider adding vitamin D deficiency to the list of factors involved in disease processes, along with the known ILD risk factors such as environmental toxins and smoking."
She said more research is needed to determine whether increasing blood vitamin D levels can prevent or slow progression of the lung disease.
About 500,000 people have interstitial lung disease in the United States, with 132,000 to 200,000 having idiopathic pulmonary fibrosis, according to the Pulmonary Fibrosis Foundation.
The disease is caused by environmental toxins, including asbestos or coal dust, but it also has been linked to autoimmune disorders, infections and medication side effects.
The average survival is three to five years, according to a study published in Dove Press.
ILD is different than lung diseases from obstructive airways.
Researchers sought to learn about potential treatable factors related to early signs of the scarring disease seen by CT scans.
"We knew that the activated vitamin D hormone has anti-inflammatory properties and helps regulate the immune system, which goes awry in ILD," Michos said. "There was also evidence in the literature that vitamin D plays a role in obstructive lung diseases such as asthma and COPD, and we now found that the association exists with this scarring form of lung disease too."
Researchers studied data from the Multi-Ethnic Study of Atherosclerosis, which from 2000 to 2002 recruited participants from several cities in the United States.
In blood samples, they found about 30 percent of the participants had vitamin D levels that were considered deficient -- less than 20 nanograms per milliliter. Those with vitamin D levels of 20-30 nanograms per milliliter were considered to have "intermediate" levels and those with 30 nanograms per milliliter or more were considered to have met recommended levels.
They also underwent heart CT scans at the first visit and some also at later visits.
Among the vitamin D-deficient participants, they had a larger volume on average -- about 2.7 centimeters cubed -- of bright spots in the lung compared with those with adequate vitamin D levels. They adjusted for age and lifestyle risk factors of lung disease, including current smoking status, past years of smoking, physical inactivity or obesity.
In examining full lung scans, those with deficient or intermediate vitamin D levels were also 50 to 60 percent more likely to have abnormalities on their full lung scans. The association was still present when adjusting for cardiovascular and inflammatory risk factors.
Vitamin D levels can be increased by spending 15 minutes a day in summer sunlight, through a diet that includes fatty fish and fortified dairy products and supplements.