People who smoke but consume three or more servings of fruit and vegetables and regularly drink green or black tea may be keeping lung cancer at bay, new research suggests.

Researchers at the University of California Los Angeles compared the eating habits of 558 people who had lung cancer versus 837 people who did not have the disease. They found that those who ate large quantities of fruit, which contains components called flavonoids, had a lower risk of developing lung cancer.

People who ate three servings of vegetables a day had 1.6-fold greater odds against developing lung cancer than those who didn't consume three servings, according to the study. Those who consumed three or more servings of fruit had one-fold greater odds against developing lung cancer.

Drinking one cup of tea a day meant study participants had 0.8-fold greater odds against developing cancer.

Flavonoids give fruit and vegetables their colours and have antioxidant and anti-inflammatory properties. The ones identified in the study as most protective were:

  • Catechin, found in strawberries; green, black teas.
  • Kaempferol, found in Brussels sprouts and apples.
  • Quercetin, found in beans, onions, apples.

In the study, the median intake of total flavonoids among controls was approximately 60 milligrams per day.

The study appears in the May issue of the journal Cancer.

"What we found was extremely interesting, that several types of flavonoids are associated with a reduced risk of lung cancer among smokers," said Dr. Zuo-Feng Zhang, a researcher at UCLA's Jonsson Cancer Center and a professor of public health and epidemiology. "The findings were especially interesting because tobacco smoking is the major risk factor for lung cancer."

"We observed inverse associations of epicatechin, catechin, quercetin, and kaempferol intakes with lung cancer among tobacco smokers," the study's authors said.

They believe that flavonoids halt the development of blood vessels connected to cancerous tumours, preventing them from infiltrating healthy tissue. However, researchers caution that more analysis is necessary.

And they also point out that quitting smoking is still the best step in lowering the risk of developing lung cancer.