(American Thoracic Society) -- Eating at least two or more apples per week and a higher intake of the essential metal selenium can protect against asthma in adults, according to British researchers.

They reported on a population-based, case-control study to determine whether asthma is less common and less severe in adults who consume more dietary antioxidants. Their analysis was done on 1,471 individuals (607 asthma patients and 864 controls without asthma). Patients were aged 16 to 50. Complete information about their usual diet was obtained through food frequency questionnaires.

The scientists found that asthma was less common in adults who consumed more apples and had a higher intake of selenium. There was also some evidence that asthma was less severe among some individuals with asthma who drank more red wine.

The researchers called the effect of dietary selenium on asthma incidence a "strong association." Dietary selenium is found in meats and other animal products. This metal is necessary for the synthesis of an essential antioxidant enzyme.

Most diets in the United States provide selenium at or above the daily requirement. But intake of selenium has been declining in Great Britain, according to the authors.

The research appears in the second of two November issues of the American Thoracic Society peer-reviewed American Journal of Respiratory and Critical Care Medicine.