Eating a diet rich in whole grains, polyunsaturated fats and nuts -- and low in red and processed meat, refined grains and sugary drinks -- is associated with a lower risk of chronic lung disease (chronic obstructive pulmonary disease or COPD), finds a study published in The BMJ this week.
The finding supports the importance of a healthy diet to promote lung health.
COPD is an umbrella term for chronic lung diseases, such as emphysema and bronchitis, which block the airways and restrict oxygen flow around the body. It is currently ranked the third leading cause of death worldwide.
The predominant risk factor for COPD in the developed world is cigarette smoking, but up to one third of COPD patients have never smoked, suggesting that other factors are involved.
A healthy diet has been consistently linked with reduced risk of heart disease and cancer, but the role of diet in risk of COPD is unknown.
So a team of researchers based in France and the USA, set out to investigate the association between the Alternate Healthy Eating Index 2010 (AHEI-2010) - a measure of diet quality based on current scientific knowledge - and the risk of COPD.
They analysed data for more than 120,000 US men and women taking part in the Nurses' Health Study from 1984 to 2000 and the Health Professionals Follow-up Study from 1986 to 1998.
Participants completed regular questionnaires on dietary intake, and those who reported a diagnosis of emphysema or chronic bronchitis between 1984 and 2000 were also assessed for COPD.
The AHEI-2010 diet score is based on 11 components, with a higher score reflecting high intakes of vegetables, whole grains, polyunsaturated fats, nuts, and long chain omega-3 fats - moderate intake of alcohol - and low intakes of red and processed meats, refined grains, and sugar sweetened drinks.
Over the study period, 723 cases of newly diagnosed COPD occurred in women and 167 in men.
After adjusting for 12 factors such as age, physical activity, body mass index, smoking and ethnicity, the risk of newly diagnosed COPD was one third lower in participants who ate the healthiest AHEI-2010 diet compared with those who ate the least healthy diet. The findings were similar in ex-smokers and current smokers - and in both women and men.
By contrast, the AHEI-2010 diet score was completely unrelated to incident asthma.
"This is a novel finding that supports the importance of diet in the pathogenesis of COPD," say the authors. "Although efforts to prevent COPD should continue to focus on smoking cessation, these prospective findings support the importance of a healthy diet in multi-interventional programs to prevent COPD."
"Our results encourage clinicians to consider the potential role of the combined effect of foods in a healthy diet in promoting lung health," they conclude.