An Australian study appears to support previous evidence linking diet to asthma outcome.
Young adults whose diet included whole milk and fruits including apples and pears were significantly less likely to have asthma or show tendency toward developing it, the researchers from University of Tasmania and Monash University in Melbourne report. Soy drinks however were linked to an increased risk of the disease.
The community-based, cross-sectional study recruited 1601 adults, with a mean age of 35, from the federal electoral rolls in Melbourne in 1999. Subjects completed questionnaires assessing their respiratory health and dietary patterns. Then they used multiple logistic regression with alternate definitions of asthma and atopy (allergy) to analyse the impact of 25 different nutrients and 47 food groups.
Whole milk was associated with a 34 per cent lower risk of current asthma, and reduced the likelihood of doctor-diagnosed asthma and atopy by almost 30 per cent, reported the researchers in this month's American Journal of Clinical Nutrition. Conversely, intake of soy beverages appeared to double the risk of current asthma.
Apples and pears also protected against current asthma, with reduced risk ratio of 0.83.
While the research identified a relationship between dairy products, soy beverages, and apples and pears, and asthma outcome, it could not link the effect to nutrients per se, said the researchers.
"Dietary modification after diagnosis is one possible explanation for this finding," they write. "Intervention studies using whole foods are required to ascertain whether such modifications of food intake could be beneficial in the prevention or amelioration of asthma."
Incidence of asthma has been climbing steadily in the Western world and is the most common long term condition in the UK today, according to the National Asthma Campaign. It is thought that modern lifestyle, including pollution and hygiene, contributes to the risk of developing asthma, and diet could also play a role in this, believe some scientists.
Research linking fruit and vegetable intake to better respiratory health points to the high flavonoid content in apples as responsible for the benefits although the current study did not point to specific nutrients.
Milk has also been found to benefit respiratory health in children, with some scientists theorising that the growing tendancy to replace dairy products with polyunsaturated fats may be a factor in rising asthma rates. A recent study from the Netherlands found that pre-school children who ate full fat milk and butter daily were less likely to develop asthma later on. Fruit juice, vegetables and fish were also associated with slightly lower rates of the respiratory disease, but these differences were not statistically significant, reported the team.