WEDNESDAY, March 11, 2020 (HealthDay News) -- A green tea extract has shown early hints of promise against a serious, progressive form of lung disease, researchers say.

The disease is called pulmonary fibrosis, where scar tissue builds up in the lungs over time, limiting the amount of oxygen the body receives. Eventually, life-threatening lung failure can develop.

There are many types of pulmonary fibrosis, but the most common is the "idiopathic" form.

"That's a fancy term doctors use when we don't know the cause," explained Dr. David Hill, a volunteer medical spokesperson for the American Lung Association.

Until a decade ago, he said, there weren't many treatments for patients with idiopathic pulmonary fibrosis (IPF), other than measures to help them manage symptoms and maintain their lung function as much as possible.

Since then, Hill said, two medications have been approved that can slow the progression of the lung scarring. They cannot, however, stop the disease.

So there is a critical need for new treatments, Hill said.

The new study is an early look at the green tea extract EGCG.

EGCG (short for epigallocatechin gallate) is a powerful antioxidant -- compounds that can help protect body cells from damage related to various disease processes.

For the study, Dr. Harold Chapman of the University of California, San Francisco, and colleagues recruited 20 patients with IPF who were scheduled to undergo lung biopsies. For two weeks, half the patients took 600 milligrams of EGCG by capsule each day; the other half did not.

When the researchers later analyzed the patients' biopsied lung tissue, they found key differences between the two groups. Patients who'd taken the supplement showed lower levels of certain proteins involved in lung fibrosis.

Their blood samples told a similar story. Levels of two proteins associated with IPF activity were lower, versus patients who did not use the green tea extract.

Hill called the findings "intriguing."

"Does this warrant looking at it in larger studies?" he said. "Sure."

But until then, Hill said, no conclusions can be drawn. This study was obviously small and short-term, and there is no proof yet that EGCG capsules can actually help IPF patients, he noted.

Dr. Gregory Cosgrove is chief medical officer of the nonprofit Pulmonary Fibrosis Foundation.

He said the researchers took a "pretty unique and clever" approach: Whereas studies typically assess an IPF treatment by giving patients breathing tests, this one looked for objective changes in lung tissue -- which, in this case, were quickly detectable.

Cosgrove agreed that the findings are "encouraging" and merit further study of the supplement's benefits and any side effects. One of the logical next questions, he said, is whether the supplement can also improve patients' breathing test performance.

For now, those questions remain open. And even though green tea extracts are readily available, that does not mean people should rush to buy them, according to Cosgrove.

"We cannot say this is an appropriate therapy for IPF," he said. "I'd hate to see patients decide they're going to take EGCG instead of proven medications."

It's estimated that about 200,000 Americans have IPF, with roughly 50,000 new cases diagnosed each year, according to the Pulmonary Fibrosis Foundation. Studies have found an average survival rate of three to five years. But the foundation says that's based on older data, and some people live much longer with the disease.

The symptoms include a persistent cough, fatigue and breathlessness during physical activity. Since other conditions can cause similar problems, Cosgrove said, pulmonary fibrosis can initially be missed.

While the precise causes of IPF are unknown, older age raises the risk, Cosgrove said. Most cases are diagnosed in people in their 60s or beyond. Smoking and a family history of IPF are also considered risk factors.

The current study was reported in a letter in the March 12 issue of the New England Journal of Medicine. It was funded by government and foundation grants. Three co-authors on the work are with Pliant Therapeutics, a South San Francisco-based company developing drugs for various fibrotic diseases.

More information

For more on pulmonary fibrosis, visit the Pulmonary Fibrosis Foundation.