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Diet may play important role in COPD prevention

High intake of fruits and vegetables significantly lowered the incidence of COPD in former and current smokers, according to findings published in Thorax.

“COPD is predicted by WHO to become the third [leading] cause of death worldwide” [by 2030], Joanna Kaluza, PhD, from the department of human nutrition at Warsaw University of Life Sciences in Poland, and colleagues wrote. “Oxidative stress induced by cigarette smoking is now recognized as a major predisposing factor in the pathogenesis of COPD. It was observed that antioxidant capacity in patients with COPD is substantially reduced as a result of cigarette smoking, with oxidative stress persisting long after the cessation of cigarette smoking, due to the continued endogenous production of reactive oxygen species. Thus, it can be hypothesized that high consumption of fruits and vegetables, a rich source of antioxidants, may protect the lung against oxidative damage and prevent COPD.”

Kaluza and colleagues investigated whether fruit and vegetable consumption is associated with COPD risk and if the association is modified by smoking status using data from the population-based prospective Cohort of Swedish Men. The cohort included 44,335 men between the ages of 45 and 79 years with no history of COPD at baseline. Participants reported their frequency of intake of 96 different fruits and vegetables through a self-administered questionnaire. They also indicated how many cigarettes they smoked daily on average during five intervals of their lifetimes — age 15 to 20 years; age 21 to 30 years; aged 31 to 40 years; age 41 to 50 years; and age 51 to 60 years). Approximately 63% of participants smoked at some point, 24% were current smokers and 38.5% never smoked. The researchers classified the participants into quintiles based on how many servings of fruits and vegetables they consumed daily. Men in the highest quintile ate 5.3 or more servings per day and those in the lowest quintile ate fewer than 2 servings per day.

During follow-up, occurring at a mean of 13.2 years, the researchers identified 1,918 incident cases of COPD. Among those in the lowest quintile of fruit and vegetable consumption, the number of new cases of COPD was estimated to be 1,166 per 100,000 person-years for current smokers and 506 per 100,000 person-years for former smokers. Among those in the highest quintile, the number of new cases of COPD was estimated to be 546 per 100,000 person-years for current smokers and 255 per 100,000 person-years for former smokers.

In smokers, the researchers found a strong inverse association between total fruit and vegetable intake and COPD; however, no such association was seen in never-smokers. Compared with men in the lowest quintile of total fruit and vegetable consumption, men in the highest quintile had a 35% lower risk for COPD (95%, CI 24-45). Individually, consumption of fruit was associated with a 27% lower risk for COPD (95%, CI 15-38), while consumption of vegetables was associated with an 18% lower risk (95%, CI 3-30) among men in the highest quintile as opposed to those in the lowest. Among all participants, men in the highest quintile had an HR for COPD of 0.6 (95%, CI 0.49-0.74) for total fruits and vegetables, 0.72 (95%, CI 0.59-0.88) for fruits and 0.79 (95%, CI 0.64-0.97) for vegetables.

Current smokers in the highest quintile for fruit and vegetable consumption were 40% less likely to develop COPD, while former smokers in the highest quintile were 34% less likely to develop COPD. Each additional daily serving of total fruit and vegetable consumption significantly reduced the risk for COPD in current smokers by 8% and in former smokers by 4%. Current and former smokers in the lowest quintile were 13.5 times and six times more likely to develop COPD, respectively, compared with those in the highest quintile who never smoked.

The researchers noted that apples, pears, green leafy vegetables and peppers had the most robust impact on COPD risk, while there were no associations observed for berry fruits, bananas, citrus fruits, cruciferous and root vegetables, tomatoes, onions, garlic or green peas.

“The present findings confirm the strong impact of cigarette smoking on the development of COPD and also indicate that a diet rich in fruit and vegetables may have an important role in prevention of COPD,” Kaluza and colleagues concluded. “Nevertheless, non-smoking and smoking cessation remain the main public health message to prevent the development of COPD.”

In a related editorial, Raphaelle Varraso, PhD, from INSERM U1168, and Seif Shaheen, MA, MRCP, MSc, PhD, FFPH, from the Queen Mary University of London, wrote that the study by Kaluza and colleagues was observational and therefore, a clinical trial is warranted to confirm their conclusions.

However, they added that, “there is nothing to be lost by acting now. We would argue that clinicians should consider the potential benefits of a healthy diet in promoting lung health, and advocate optimizing intake of fruits and vegetables, especially in smokers who are unable to stop smoking.” – by Alaina Tedesco

Disclosures: Kaluza and colleagues report receiving support from a research grant from the Swedish Research Council/Infrastructure, the Karolinska Institutet’s Distinguished Professor Award, the Swedish Heat-Lung Foundation and King Gustav V’s and Queen Victoria’s Freemason Research Foundation. Varraso and Shaheen report no relevant financial disclosures.