Adhering to a healthy diet — be it a Mediterranean diet, a prudent diet, or a diet supported by health associations — significantly lowers the risk of chronic obstructive pulmonary disease (COPD), a recent meta-analysis suggests.
Unhealthy diets, such as the Western diet, appear to increase this risk, but the findings failed to reach statistical significance. Additional studies that follow people on specific diets over long periods of time are needed to further understand the effects of diet on COPD.
The study, “Relationship between dietary patterns and COPD: a systematic review and meta-analysis,” was published in the journal ERJ Open Research.
While exposure to tobacco smoke is a major driver of COPD, with several current efforts to curb the disease focusing on smoking cessation, some people who develop the condition have never smoked. This suggests that other risk factors also may contribute to disease development and progression.
Diet may be among modifiable risk factors for COPD, as some review studies report that eating a high fruit and vegetable diet rich in antioxidants is associated with a decreased incidence of COPD. These studies, however, have examined the intake of specific foods or nutrients, rather than looking at the dietary patterns of people, which are easier to understand and implement.
Researchers at McMaster University, Canada, conducted a systematic review of studies, published over the past four decades, that examined the relationship between dietary patterns and COPD measures, such as incidence (number of new cases), prevalence (number of total cases), quality of life, lung function, and mortality.
The final analysis involved eight studies, published from 2007 to 2019, including five cross-sectional studies (which examine a population at a given point in time), and three cohort studies (which examine a group of people over time). Among them, three studies were deemed “good” in terms of quality assessments; the remaining were “fair” in quality, with several concerns in their design.
All eight studies examined the impact of a healthy diet in COPD, and three of them also investigated the effects of unhealthy diets. The diets varied from study to study, but healthy ones included the mediterranean diet, the prudent diet, and diets recommended by health organizations. The Western diet and diets rich in carbohydrates or refined foods were considered unhealthy.
None of these studies reported on quality of life or mortality.
Results showed that adhering to healthy diets significantly lowered the risk of COPD, and that even though the opposite trend was observed for unhealthy diets, the results failed to reach statistical significance.
One study also examined changes in lung function assessed via spirometry, according to a person’s adherence to a healthy diet called Dietary Approaches to Stop Hypertension (DASH). Results showed that in COPD patients, lung function outcomes did not correlate with adherence to diet. But in controls without COPD, adherence to the DASH diet was associated with a significant decrease in the ratio of forced expiratory volume in one second over the forced vital capacity — a ratio that indicates more lung obstruction.
“Overall, adherence to a healthy dietary pattern was associated with a lower prevalence of COPD, whereas adhering to an unhealthy dietary pattern was associated with a higher prevalence of COPD (statistically not significant),” the researchers wrote.
The team, however, noted several limitations to its study, including the large heterogeneity (diversity) between the included studies.
Researchers emphasized that “more studies, particularly adequately powered longitudinal [over time] studies, are needed to further elucidate the effects of healthy and unhealthy dietary patterns on risk of COPD.”
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