BMJ: A diet rich in fruit and vegetables is linked to a significantly lower risk of developing chronic lung disease (COPD) in former and current smokers, finds research published online in the journal Thorax. Each additional daily serving was associated with a 4-8% lower risk, the findings show. COPD, short for chronic obstructive pulmonary disease, is an umbrella term for respiratory conditions that narrow the airways, which include bronchitis and emphysema.
The primary risk factor for its development is smoking, and the World
Health Organization predicts that COPD is set to become the third
leading cause of death worldwide.
Recent evidence suggests that diet may be an important factor in the development and/or prevention of COPD.
To try and find out if fruit and vegetable intake might have a
dietary role, the researchers tracked the respiratory health of more
than 44,000 men aged between 45 and 79 for 13 years up to the end of
The sample was drawn from all men who had been born between 1918 and
1952 in central Sweden. They completed a food frequency questionnaire
detailing how often they consumed 96 different food items in 1997, at
the start of the study.
They were also quizzed about other potentially important factors,
such as educational attainment, weight, height, physical activity and
inactivity levels and how much, and how often, they drank alcohol.
And they were asked how many daily cigarettes they smoked, on
average, between the ages of 15 and 20; 21 and 30; 31 and 40; 41 and 50;
and 51 and 60.
Almost two thirds of the men (nearly 63%) had smoked at some point;
around one in four (24%) were current smokers; and nearly four out of 10
(38.5%) had never smoked.
During the monitoring period, 1918 new cases of COPD were diagnosed.
The number of new cases in current and former smokers was estimated to
be 1166 and 506/100,000 people, respectively, among those eating fewer
than 2 daily portions of fruit and vegetables; but in those eating more
than 5, the equivalent figures were 546 and 255.
In all, those eating 5 or more daily servings were 35% less likely to
develop lung disease than those eating 2 or fewer daily servings.
And when the data were stratified by smoking, current and former
smokers eating 5 or more portions of fruit and vegetables every day
were, respectively, 40% and 34%, less likely to develop COPD.
Each additional serving was associated with a 4% lower risk of COPD in former smokers and an 8% lower risk in current smokers.
Compared with those who had never smoked and who ate 5 or more
portions of fruit and vegetables, current and former smokers eating
fewer than 2 daily portions were, respectively, 13.5 times and 6 times
more likely to develop COPD.
Those at the high end of the consumption scale were 7.5 times
(current smokers), and more than 3.5 times (former smokers), as likely
to develop COPD.
Apples or pears; green leafy vegetables; and peppers seemed to exert
the strongest influence on risk, but no such associations were seen for
berry fruits; bananas; citrus fruits; cruciferous and root vegetables;
tomatoes; onions; garlic; or green peas.
As oxidative tissue stress and inflammation may be involved in COPD
development, and smoking is a potent trigger of these processes, the
antioxidants abundant in fruit and vegetables may curb their impact,
suggest the researchers, who add that smoking cessation should still
continue to be promoted as the mainstay of prevention.
But in a linked editorial, Drs Raphaelle Varraso and Seif Shaheen
emphasise that as this is an observational study, no firm conclusions
can be drawn about cause and effect; a clinical trial would be needed
But they write: “it could be argued 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 optimising intake of fruits and vegetables, especially in
smokers who are unable to stop smoking.”