Smoking is the primary cause of chronic obstructive pulmonary disease in the US, accounting for 80-90% of all cases. For the remaining 10-20%, it is believed exposure to air pollution, secondhand smoke and genetic factors are involved. But in a new study published in The BMJ, researchers suggest an unhealthy diet could be a contributing factor.
While smoking is known to be the main cause of COPD, the study authors - from France and the US - say little research has looked at what other modifiable risk factors play a role. "Diet is one such factor," they note. "Prospective data on the association between diet and the risk of COPD remain scarce, compared with the extensive literature on cardiovascular diseases or cancer."
With this in mind, the team assessed the effects of diet on the risk of COPD among 73,228 women who took part in the Nurses' Health Study from 1984 to 2000, and 47,026 men who took part in the Health Professionals Follow-Up Study from 1986 to 1998.
The researchers used the Alternate Healthy Eating Index 2010 (AHEI-2010) to measure the participants' diet quality. A higher AHEI-2010 score represents a healthy diet with a high intake of vegetables, whole grains, polyunsaturated fats, nuts and omega-3 fatty acids, a low intake of red and processed meats, refined grains and sugary drinks, and moderate alcohol consumption.
The researchers found that participants with the highest AHEI-2010 scores were a third less likely to develop COPD, compared with participants with the lowest scores, suggesting a healthy diet may reduce the risk of developing COPD.