N° 17 | November 2007

Prudent diet may help lower risk of chronic obstructive pulmonary disease

Consuming a diet rich in fruits, vegetables, whole grains and fish – labeled the “prudent diet” – may do more than help you lose a few pounds. We recently reported that the prudent diet might reduce the risk of chronic obstructive pulmonary disease (COPD) by half.

Data were collected from a large prospective cohort of US male health professionals, aged 40-75 years (Health Professionals Follow-up Study). Men answered a detailed questionnaire that included a diet survey and items on lifestyle practice (e.g., smoking habits, physical activity, weight) and medical history. Follow-up questionnaires were sent every two years thereafter to update information. Dietary intake data were collected in 1986, and every 4 years thereafter. Dietary patterns were identified from food frequency questionnaires administrated in 1986, 1990 and 1994 using principal component analysis. Two dietary patterns were identified: the prudent diet (characterized by a high intake of fruits, vegetables, fish and whole grain products) and a Western diet (characterized by a high intake of refined grains, cured and red meats, desserts and French fries).

Between 1986 and 1998, we identified 111 self-reported cases of newly diagnosed COPD among 42,917 men. The prudent diet was inversely associated with the risk of newly diagnosed COPD, and even after adjusting for age, smoking and other COPD risk factors, we found that the more strictly a person followed this dietary pattern, the lower their risk for COPD – by a full 50% for the most healthful eaters.

On the other hand, we also found that the "Western" diet (high in refined grains, cured and red meats, fried foods and sweets) appeared to significantly increase COPD risk. One-fifth of the men who indulged most heavily in the Western diet were found to have more than four times the risk for COPD than those who ate least like the Western diet.

Currently, chronic obstructive pulmonary disease (COPD) is the fourth leading cause of mortality in Europe and in the United States. With the increase in cigarette smoking in developing countries, COPD is expected to become the third leading cause of death worldwide by 2020. Cigarette smoking is the most important risk factor for COPD in developed nations, but not all smokers develop COPD, suggesting that others risk factors also are involved. Among environmental factors, changes in diet have been evoked. Several foods have been associated with chronic obstructive pulmonary disease (COPD) symptoms or lung function, however, all of these studies focused on individual nutrients or foods. Because foods are consumed together and nutrients may interact together, we decided to investigate dietary patterns that provide a broader picture of diet.

The finding that prudent diet (including fruits and vegetables) is associated with a decreased risk of newly diagnosed COPD is consistent with prior epidemiological studies. There are several papers in the literature suggesting a beneficial effect of antioxidants, particularly vitamin C, and to a lesser extent vitamin E on COPD or lung function. By contrast, the Western dietary pattern is highly loaded by processed meats, which one of the most important compound is nitrites. The Western dietary pattern also was loaded by a high intake of foods with a high glycemic index (refined grains, desserts, sweets). It has been suggested that hyperglycemia is related to an impaired lung function. As several foods (e.g., cured meat, refined grains) from the Western diet might be related to COPD, the Western pattern offers a good way to summarize the possible effects of these diverse but highly correlated foods.

Dietary pattern also seemed to go hand-in-hand with other risk-increasing lifestyle choices: we reported that the men who most heavily followed the “Western” diet also had the highest body mass index (BMI), were the least physically active and more likely to smoke, while those inclined toward the "Prudent" diet were more physically active and less likely to be current smokers.

Confirmation of these findings in other populations, particularly with different dietary habits, is warranted. These data provide additional evidence regarding the potential benefits of a diet rich in fruits and vegetables and the potential harms of more traditional Western diet. The most important public health message remains smoking cessation but these data suggest that diet, another modifiable risk factor, might also affect COPD risk.