Researchers in the Netherlands have found that apples, pears and other fruits rich in certain plant compounds may help protect the lungs from chronic disease. According to their research, the benefit might come from catechins, one of a large group of plant compounds called flavonoids that has already been linked to a lower risk of heart disease and certain cancers.
Various flavonoids have been found to act as cell-protecting antioxidants, and some research suggests antioxidants may guard against lung disease. In addition, one study has suggested that "solid fruits," including apples and pears, help protect the lungs due to their high flavonoid content, according to investigators led by Cora Tabak of the National Institute of Public Health and the Environment in Bilthoven.
To further study the possibility, Tabak's team analysed data on nearly 14,000 adults in a study on risk factors for chronic disease. They looked at the relationship between intake of different flavonoids and symptoms of chronic obstructive pulmonary disease (COPD), such as chronic coughing and breathlessness. COPD includes two serious lung diseases, chronic bronchitis and emphysema, for which cigarette smoking is the biggest risk factor.
The investigators found that people with higher catechin intakes had a lower risk of chronic cough and breathlessness, even after smoking, age, body mass and other factors were considered. Two other groups of flavonoids, flavonols and flavones, were associated with a lower risk of chronic cough only.
The main catechin sources for the study participants were tea and apples. Tea was also the biggest source of the other flavonoids studied. Yet when the researchers looked at tea alone, they found no relationship between higher consumption and lower lung disease risk. On the other hand, greater intake of solid fruits, such as apples and pears, was linked to healthier lung function.
"This first study on intake of catechins, flavonols, and flavones in relation to COPD suggests a beneficial effect of a high intake of catechins," Tabak and colleagues said. However, according to the authors, the lack of a relationship between lung disease and intake of tea and flavonoids other than catechins is puzzling. This suggests that catechins may not, on their own, lead to better lung function. They call for further research to confirm their findings and to delve deeper into the biological workings of various flavonoids.
In the study, participants gave dietary information for the previous year, answered questions on chronic respiratory symptoms, and had their lung function tested. They were split into five groups based on their various flavonoid intakes. In the group with the highest catechin intake, half of the participants consumed more than 20 milligrams of the substance each day. According to the researchers, there are about 15 milligrams of catechins in two apples.