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), as a recent meta-analysis suggests.
Unhealthy diets like the Western diet seem to increase this risk, but the results did not reach statistical significance. Additional studies, accompanying people on certain diets for long periods of time, are needed to better understand the effects of the diet on COPD.
The study, "Relationship between dietary habits and COPD: a systematic review and meta-analysisWas published in the journal ERJ Open Research.
While exposure to tobacco smoke is a major driver of COPD, some people who develop the disease have never smoked as several efforts are currently being made to contain the disease that focus on smoking cessation. This suggests that other risk factors may also contribute to the development and progression of the disease.
Diet can be one of the modifiable risk factors for COPD, as some review studies report that eating an antioxidant-rich fruit and vegetable diet is associated with a reduced incidence of COPD. However, these studies have looked at the intake of certain foods or nutrients, rather than looking at people's eating patterns that are easier to understand and implement.
Researchers from McMaster University, Canada, conducted a systematic review of the studies published over the past four decades that looked at the relationship between dietary habits and COPD measures such as incidence (number of new cases), prevalence (number of all cases). Quality of life, lung function, and mortality.
The final analysis included eight studies published from 2007 to 2019, including five cross-sectional studies (that examine a population at a point in time) and three cohort studies (that examine a group of people over time). Among them, three studies were rated “good” in terms of quality ratings. The rest were of "fair" quality and had some concerns about their design.
All eight studies looked at the effects of a healthy diet on COPD, and three of them also looked at the effects of an unhealthy diet. Diets varied from study to study, but healthy diets included the Mediterranean diet, the prudent diet, and diets recommended by health organizations. Western diets and diets high in carbohydrates or refined foods were considered unhealthy.
ne of these studies reported quality of life or mortality.
The results showed that following healthy diets significantly reduced the risk of COPD and that the results did not reach statistical significance, although the opposite trend was observed with unhealthy diets.
One study also looked at changes in lung function, as assessed by spirometry, corresponding to a person's adherence to a healthy diet known as Dietary Approaches to Cessation of High Blood Pressure (DASH). The results showed that in COPD patients, lung function results did not correlate with dietary compliance. In controls without COPD, however, adherence to the DASH diet was associated with a significant decrease in the ratio of forced expiratory volume in one second to forced vital capacity – a ratio that indicates greater pulmonary obstruction.
"Overall, following a healthy diet was associated with a lower prevalence of COPD, while following an unhealthy diet was associated with a higher prevalence of COPD (not statistically significant)," the researchers wrote.
However, the team noted some limitations to their study, including the large amount of heterogeneity (diversity) between the included studies.
The researchers stressed that "more studies are needed, particularly longitudinal studies with sufficient performance (over time) to further examine the effects of healthy and unhealthy eating habits on COPD risk."
Inês received her PhD in Biomedicine from the University of Lisbon, Portugal, where she specialized in blood vessel biology, blood stem cells and cancer. Before that, she studied cell and molecular biology at the Universidade va de Lisboa and worked as a research assistant at the Faculdade de Ciências e Tecnologias and at the Instituto Gulbenkian de Ciência.
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Patrícia received her PhD in Medical Microbiology and Infectious Diseases from the Medical Center of Leiden University in Leiden, The Netherlands. She studied applied biology at the Universidade do Minho and was a postdoctoral fellow at the Instituto de Medicina Molecular in Lisbon, Portugal. Her work focused on the molecular genetic characteristics of infectious agents such as viruses and parasites.