From cutting skin cancer risk in half to supporting the immune system, a diet rich in tomatoes and fruits imparts many health benefits. Now, researchers have found that these foods may restore lung function in ex-smokers and slow lung function decline in all adults.

The Johns Hopkins Bloomberg School of Public Health in Baltimore, MD, conducted the study. The findings were published in the European Respiratory Journal.

Around 36.5 million adults in the United States smoke cigarettes, according to the Centers for Disease Control and Prevention (CDC), and the practice causes more than 480,000 deaths per year.

Every year, around 55.4% of all adult smokers attempt to quit smoking. Smoking cessation dramatically reduces the risk of disease, including lung diseases such as chronic obstructive pulmonary disease (COPD) and lung cancer, as well as early death.

Lung health after stopping smoking has been a topic that has garnered interest among ex-smokers and health professionals alike.

The lungs begin to heal as soon as smoking is ceased. While the response is quick to start, lung improvement is incremental and can take many years. Furthermore, quitting smoking alone does not entirely erase the risk of developing a smoking-related lung disease.

Another factor to consider is that the lungs are fully mature by 20–25 years of age. After 35 years old, lung function begins to decline, and breathing becomes gradually more difficult.

In a nutshell: the diaphragm weakens, which decreases the ability to breathe in and out; muscles that keep airways open lose elasticity; alveoli lose their shape; and the area of the brain that regulates breathing sends weaker signals to the lungs.

Previous research published by The BMJ has demonstrated that a diet rich in fruits and vegetables may reduce the risk of COPD in current and former smokers. In fact, each extra daily serving was linked to a 4%–8% lower risk.

The new study goes one step further to suggest that consuming a diet high in fruits and vegetables—particularly tomatoes and apples—slows down the decline in lung function among ex-smokers over the duration of 10 years.

Slower lung deterioration among all adults

Compared with adults who consumed fewer than one serving of fruit or one tomato per day, those who ate more than three portions of fruit or more than two tomatoes experienced slower lung function decline.

The scientists asked questions about other dietary and processed sources of fruits and vegetables, such as tomato sauce, but the protective effect was only apparent among those who ate fresh fruits and vegetables.

This finding suggests that there may be particular components in fresh tomatoes and apples that help to repair the lung damage that results from smoking.

What is more, a slower deterioration in lung function was observed in all adults in the study who ate a tomato-rich diet—including those who had never smoked.

"This study," says lead study author Vanessa Garcia-Larsen, who works as an assistant professor in the Bloomberg School's Department of International Health, "shows that diet might help repair lung damage in people who have stopped smoking. It also suggests that a diet rich in fruits can slow down the lung's natural aging process even if you have never smoked."

"The findings," she adds, "support the need for dietary recommendations, especially for people at risk of developing respiratory diseases such as COPD."

Diet could help to combat COPD

Garcia-Larsen and her team evaluated diet and performed lung function tests, including spirometry, among more than 650 adults from Germany, Norway, and the United Kingdom in 2002 and again 10 years later.

The connection between diet and lung function was most pronounced among ex-smokers. When the volume of air they could inhale was measured, former smokers who consumed a tomato- and fruit-rich diet had around 80 milliliter slower decline in lung function over 10 years. This indicates that specific nutrients could be playing a role in healing the damage caused by smoking.

"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."

Vanessa Garcia-Larsen

The study controlled for factors such as age, sex, height, body mass index (BMI), total energy intake, and physical activity to ensure that the results were not skewed.