Processed and cured meats may worsen asthma problems

People with asthma may find their symptoms worsen if they eat too much cured and processed meats such as ham and salami, new research suggests.

Servings of four or more a week - considered to be a high dietary intake - seems to have the greatest impact on symptoms, the findings published online in the journal Thorax suggested.

Such meat is rich in nitrites, which may have a role in airway inflammation - a typical feature of asthma, the report said.

Researchers looked at a study of 971 adults picked from data tracking 2,000 asthma patients, close relatives and a comparison group from five cities in France for more than 20 years.

Looking at specific data between 2011 and 2013, the researchers measured dietary intake through frequent questionnaires taking in 118 items in 46 food groups and graded cured meat weekly intake from low - one or less - to high - four or more.

Asthma symptoms, such as difficulty breathing, chest tightness and shortness of breath, in the preceding 12 months were scored from zero to five. 

Other information such as smoking, regular physical activity, age, sex and educational attainment was also taken into account

Between 2003 and 2007, 42% of the participants said they had asthma at some point and around half (51%) had never smoked. 

Among those who ate one or fewer weekly servings, the proportion of those with worsening asthma symptoms was 14% while among those eating one to four the proportion was 20% and among those eating four or more, the proportion was 22%.

After potentially influential factors were taken into account, the researchers believed that those who ate the most cured meats were 76% more likely to experience worsening asthma symptoms than those who ate the least.

The study was observational so no firm conclusions could be drawn.

The researchers said the symptom score may have been affected by smoking or COPD - chronic lung disease that shares many of its symptoms with asthma.

Nitrites are also believed to be, under certain conditions, carcinogenic to humans.