By Pat Hagan
LONDON (Reuters Health) - Eating oily fish like salmon of mackerel regularly may reduce the risk of asthma symptoms, according to new British research.
A study by public health experts at the University of Cambridge suggests regular consumption of fish like salmon, mackerel and herring can have a protective effect. It is the latest evidence that diet is important in determining who is most at risk of developing asthma, and adds to the list of benefits ascribed to fish rich in omega-3 fatty acids.
"This study adds to existing evidence that a diet high in oily fish could protect against asthma," said the National Asthma Campaign in a statement released in response to the study.
"There have now been several studies suggesting an association between intake of certain foods and a lower incidence of asthma. These have shown a potential association between intake of oily fish, fresh fruit and magnesium--which is found in fresh fruit and vegetables and reduced by cooking--and a lower rate of asthma," the National Asthma Campaign statement notes.
The results add to the argument that lifestyle changes could be one reason that asthma rates are increasing.
A team of researchers from the university studied more than 750 volunteers who were already taking part in a much bigger investigation called the European Prospective Investigation of Cancer--a long-term study into the effects of diet on cancer.
They provided details of diet and lifestyles and were also asked if they had even been diagnosed with asthma.
The results revealed 333 patients had suffered wheezing in the 12 months before completing their questionnaire and 437 had not.
More than 12% of the healthy volunteers reported eating oily fish at least twice a week, compared with just 7.5% of the asthma sufferers.
After accounting for other asthma risk factors, such as body mass index, social class and smoking habits, the researchers found regular fish consumption roughly halved the risk of asthma attacks, wheezing or waking up with tightness in the chest.
"These data support the hypothesis that regular consumption of oily fish may be protective against symptomatic asthma," the researchers said in a report at the recent British Thoracic Society Winter meeting in London.
How the polyunsaturated fatty acids in these fish protect against asthma remains unknown, but scientists speculate it may to do with reducing production of prostaglandins linked with constriction of the airways.
Eating oily fish has also been linked to protection from heart disease, arthritis and other ailments, although the British government currently recommends limiting consumption of oily fish to one portion a week, as the flesh may contain high concentrations of heavy metals such as mercury, as well as dioxin pollutants.