Writing in the journal Thorax, lead author Raphaelle Varraso states that dietary patterns similar to the Med diet were associated with a significant decrease in COPD risk, while dietary patterns similar to the Western style were associated with a significant increase in newly diagnosed COPD.

The Med diet, rich in cereals, wine, fruits, nuts, legumes and whole grains, fish and olive oil, has been linked to longer life, less heart disease, and protection against some cancers. The diet's main nutritional components include beta-carotene, vitamin C, tocopherols, polyphenols, and essential minerals.

It is these antioxidants and polyphenols that appear to offer protection, wrote the researchers in the British Medical Journal Thorax.

"The finding that the [Mediterranean diet] pattern is associated with a decreased risk of newly diagnosed COPD is consistent with previous epidemiological literature suggesting a beneficial effect of antioxidants - particularly vitamin C and, to a lesser extent, vitamin E - on COPD," wrote the researchers.

COPD mainly affects smokers, and is the number five cause of deathworldwide. It is characterised by chronic inflammation in the small airwaysof the lung and leads to excessive mucus production, excessive fibrousconnective tissue development (fibrosis), and degradation of proteins (proteolysis). There is no cure.

The researchers used dietary data on 42,917 men (age range 40-75) collected using a 131-item food frequency questionnaire. Over 12 years of follow-up, 111 self-reported cases of newly diagnosed COPD were identified.

Greater adherence to the Med diet was associated with a 50 per cent reduction in COPD risk, comparing those with the greater to lowest adherence. On the other hand, the Western pattern was associated with a 356 per cent increase in the risk of newly diagnosed COPD.

"The Western diet is highly loaded with by processed meats, one of the most important compounds of which is nitrite," said the researchers. "Nitrites generate reactive nitrogen species which provoke nitorsative stress; this may contribute to the progressive deterioration in pulmonary function."

They also noted that the high glycaemic load of the Western diet has also been linked to impaired lung function.

"In men, a diet rich in fruits, vegetables and fish may reduce risk of COPD, whereas a diet rich in refined grains, cured and red meats, desserts and French fries may increase risk of COPD," they concluded.

Source: Thorax (British Medical Journal)
Online First 2007, doi:10.1136/thx.2006.074534
"Prospective study of dietary patterns and chronic obstructive pulmonary disease among US men"
Authors: R. Varraso, T.T. Fung, F.B. Hu, W. Willett, C.A. Camargo