Do Mediterranean diets cut COPD?

Risk of COPD may be reduced by eating a Mediterranean diet, Sanjay Tanday reports

What is the story?
Eating a diet rich in Mediterranean foods, such as fruit, vegetables, fish and olive oil, can reduce the risk of developing serious lung disease, according to media reports.

A Mediterranean diet was found to halve the risk of developing COPD when compared with a Western diet.

COPD kills more than 30,000 people in Britain each year and it is expected to become the world’s third leading cause of death by 2020.

Previous research has shown that a Mediterranean diet can reduce the risk of developing asthma and respiratory allergies in children, but this is the first study to examine the link between diet and COPD. The French researchers proposed that a Mediterranean diet, rich in antioxidants, could lower the risk of COPD by reducing tissue inflammation.

In contrast, a typical Western diet was found to be high in nitrates that may contribute to a progressive deterioration of lung function, say the papers.

What is the research?
The reports are based on findings from a prospective cohort study of US men.

The 12-year study included 42,917 men aged 40–75 who were free of COPD at baseline.

Participants completed a detailed questionnaire on diet, medical history and lifestyle, including smoking status and physical activity.

Every two years questionnaires on smoking habits, physical activity, weight and other risk factors were completed.

Dietary intake was collected every four years using a 131-item food frequency questionnaire.

Two distinct eating patterns were evident. Some of the men ate a Mediterranean diet containing plenty of fruit, vegetables, whole grains and fish.

The others ate a Western diet full of processed food, refined sugar, cured meats and red meats.

Over the course of the study, 111 cases of COPD were diagnosed. Men in the highest quintile of Mediterranean diet intake were 50 per cent less likely to develop COPD than those in the lowest quintile.

This was the case even after adjustment for smoking and age.

Men who ate a predominantly Western diet were more than four times as likely to develop COPD than those on the Mediterranean diet.

Due to the potential overlap between the diagnoses of COPD and asthma, the researchers examined the relationship between dietary patterns and the incidence of asthma in this cohort of men.

No relationship was found between either of the diets and the risk of adult-onset asthma.

What do researchers say?
Lead researcher Dr Raphaelle Varraso, from the department of nutrition at the Harvard School of Public Health, Boston, said: ‘Studies on the association of individual foods and nutrients and COPD have suggested a beneficial effect of antioxidants, particularly vitamin C and to a lesser extent vitamin E, on COPD and FEV1 level.

‘However, there is no clear association between one particular food and COPD.’

The effect of any individual nutrient on the risk of COPD may be too small to detect. But when several nutrients are consumed together, the cumulative effect may be sufficient for detection, he said.

Dr Varraso proposed that the nitrates that were found in the Western diet could be to blame for the increased risk of COPD in the West.

‘Nitrates generate reactive nitrogen species which provoke nitrosative stress. This may contribute to the progressive deterioration of pulmonary function,’ he said.

What other researchers say
Dr Keith Prowse, chairman of the British Lung Foundation, said the study provided an interesting insight into a possible link between diet and COPD.

‘COPD is the only major cause of death of which incidence is on the increase in the UK and we urgently need more research into all aspects of the disease so that health services can prevent and treat it more effectively,’ said Dr Prowse.

What the papers said

“Mediterranean diet cuts the risk of lung disease”

“Med diet cuts lung disease risk”

“Mediterranean diet halves risk of lung disease”

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