A Mediterranean diet halves the chances of developing progressive inflammatory lung disease (COPD), reveals a large study, published ahead of print in Thorax.

COPD (chronic obstructive pulmonary disease) is an umbrella term for chronic progressive lung disease, such as emphysema and bronchitis. It is expected to become the third leading cause of death worldwide by 2020, with cigarette smoking the primary factor in its development.

The researchers tracked the health of almost 43,000 men, who were already part of the US Health Professionals Follow up Study. This began in 1986 and involved more than 50,000 US health care professionals aged between 40 and 75, who were surveyed every two years.

They were asked questions about lifestyle, including smoking and exercise, diet and medical history. Dietary intake was assessed in detail every four years.

Eating patterns fell into two distinct categories: those who ate a diet rich in fruit, vegetables, whole grains and fish (Mediterranean diet); and those who ate a diet rich in processed foods, refined sugars, and cured and red meats (Western diet).

Between 1986 and 1998, 111 cases of COPD were newly diagnosed.

The Mediterranean diet was associated with a 50% lower risk of developing COPD than the Western diet, even after adjusting for age, smoking, and other risk factors.

And men who ate a predominantly Western diet were more than four times as likely to develop COPD, even after taking account of other influential factors.

The higher the compliance with a Mediterranean diet, the lower was the risk of developing COPD over the 12 year period.

Conversely, the higher the compliance with the Western diet, the higher was the risk of developing COPD.