A decades-long study about the impact of food on asthmatics has found that eating processed meat often might worsen asthma and its symptoms such as an intense difficulty in breathing.
Consuming more than four portions of processed meats a week is a risk, suggests the study of nearly 1,000 French persons published in the scientific journal Thorax. Processed meat is already linked to causing cancer.
Researchers in the asthma study believe the triggering of asthma symptoms by eating too much processed mean might be caused by a preservative called nitrite or sodium nitrite used in meats such as ham and sausages. Nitrites, which are frequently added to processed or cured meats as a preservative, aggravate the airways and seem to trigger asthma in sufferers.
Under certain conditions in the human body, nitrites can damage cells and transform into molecules that cause cancer.
Experts say persons with and without asthma should eat no more than 70 grams a day of red and processed meat for good health. That's the equivalent of one sausage plus a thin slice of bacon a day.
The participants in the study took part in a French survey about food and health, lasting from 2003 to 2013. Around half of these participants were asthma patients. The rest, or the control subjects, had no history of asthma.
The survey looked specifically at asthma symptoms such as breathlessness, wheezing and chest tightness and the intake of processed meat. The meat portions in the study consisted of a single portion of two slices of ham, one sausage or two slices of salami.
Among participants with asthma, higher meat consumption was linked with a worsening of their asthma symptoms.
People who said they ate more than four portions a week (or eight slices of ham or four sausages, for example) had their asthma worsen the most by the end of the study.
Experts that worked on the study, however, emphasized their work can't prove diet is definitely to blame. There are lots of factors in a person's life that can worsen asthma.
Researchers, however, tried to eliminate the most obvious ones. They also controlled for other factors such as obesity. Despite these measures, the link between processed meat and worsening asthma remained.
"Although certain foods can be triggers for allergies in some people, there is no specific dietary advice to manage asthma symptoms generally," said Dr. Erika Kennington, Head of Research at Asthma UK.
"For most people with asthma, healthy eating advice is exactly the same as it is for everyone else: follow a balanced diet that includes plenty of fresh and unprocessed food and is low in sugar, salt and saturated fat."