Ex-smokers with a diet high in tomatoes and fruit, especially apples, experience a slower decline in lung function as they age, a study suggests.

The findings raise the possibility that the nutrients in these foods might help restore lung tissue that has been damaged by smoking.

Researchers found that adults who ate more than two tomatoes or three portions of fresh fruit a day on average had a slower decline in lung function than those who ate less than one tomato or less than one portion of fruit a day.

The protective effect surfaced only with fresh fruit and vegetables, not in cooked dishes, like tomato sauce, nor in processed foods containing fruits and vegetables. The highest tomato consumption was linked to a slower decline in lung function among all adults, including both never-smokers and ex-smokers.

“This study shows that diet might help repair lung damage in people who have stopped smoking,” said Vanessa Garcia-Larsen, assistant professor of international health in the Johns Hopkins University Bloomberg School of Public Health.

“It also suggests that a diet rich in fruits can slow down the lung’s natural aging process, even if you have never smoked,” said Garcia-Larsen, the study’s lead author. “The findings support the need for dietary recommendations, especially for people at risk of developing respiratory diseases such as COPD.”

Poor lung function is linked with mortality risks from all diseases, including chronic obstructive pulmonary disease, heart disease, and lung cancer.

The researchers measured how much air each person could expel from their lungs in one second and how much they could inhale in six seconds. The study controlled for age, height, sex, body mass index, socioeconomic status, physical activity, and total energy intake.

The strikingly slower decline in lung function among former smokers who ate a diet high in tomatoes and fruit, especially apples, suggests that nutrients in their diets are helping to repair damage done by smoking, Garcia-Larsen says.

“Lung function starts to decline at around age 30, at a variable speed depending on the general and specific health of individuals,” she explained. “Our study suggests that eating more fruits on a regular basis can help attenuate the decline as people age, and might even help repair damage caused by smoking. Diet could become one way of combating rising diagnosis of COPD around the world.”