Eating large amounts of processed meats, such as ham, sausage and salami, may worsen the symptoms of asthma, a new study has found.

According to the findings, four or more servings of cured and processed meats per week appear to have the greatest impact on the lung condition.

French researchers set out to determine whether processed meats could worsen asthma symptoms over time by following the progress of almost 1,000 adults between 2003 and 2013.

Dietary intake was monitored using food frequency questionnaires. Processed meat intake was classified as low (one or less servings per week), medium (one to four servings per week) or high (four or more per week).

The study found that the more processed meat a person with asthma consumed, the more likely they were to experience a worsening of symptoms.

In fact, after taking into account factors which could have influenced the results, such as smoking and exercise, the researchers found that those who consumed the most processed meats were 76% more likely to experience a worsening of their asthma symptoms compared to those who consumed the least.

They noted that cured and processed meats are rich in nitrates, which may have a role to play in the inflammation of the airways - a typical feature of asthma.

The researchers from the Paul Brousse Hospital in Villejuif acknowledged that this was an observational study, so no firm conclusions can be drawn about cause and effect. However, they noted that research in other countries has also suggested that processed meats may have an impact on lung function.

"This research extends the deleterious effect of cured meat on health, and the effect of diet on asthma in adults," they commented.

Details of these findings are published in the journal, Thorax.