Apples, Selenium May Lower Asthma Risk

NEW YORK (Reuters Health) - A new UK study links intake of apples and the mineral selenium to a lower risk of asthma, suggesting that certain antioxidants may protect the lungs from disease.

Antioxidants help neutralize damaging forms of oxygen that arise from normal metabolism. These free radicals are unstable compounds that can damage cells and are thought to contribute to chronic disease.

Researchers have speculated that antioxidants may protect lung health, including lowering the risk of asthma. But studies on antioxidants like vitamins C and E have produced conflicting results. And even less is known about other antioxidants, such as plant compounds called flavonoids and trace minerals like selenium, according to Dr. Seif O. Shaheen and colleagues.

To see how dietary antioxidants affect asthma risk and severity, Shaheen's team surveyed nearly 1,500 UK adults about their eating habits during the previous year. They focused particularly on intakes of fruits and vegetables, flavonoid-rich foods like apples, onions, tea and red wine, antioxidant vitamins, and trace elements that act as antioxidant enzymes--such as selenium, zinc and copper.

The investigators found that people who ate at least two apples per week faced a 22%- to 32% lower asthma risk than those who ate fewer.

And as selenium intake increased, asthma risk declined, according to findings published in a recent issue of the American Journal of Respiratory and Critical Care Medicine. Participants with the highest intakes--54 to 90 micrograms a day--were only about half as likely to have asthma as those who consumed the least selenium, about 23 to 30 micrograms daily. The US recommended daily intake for selenium is 55 micrograms.

Red wine intake was associated with a reduction in the severity of asthma, according to Shaheen and colleagues from King's College in London and the University of Southampton.

``The associations between apple and red wine consumption and asthma may indicate a protective effect of flavonoids,'' the researchers write.

They speculate that certain subtypes of flavonoids may be key in this protection since other flavonoid-containing foods did not affect asthma risk or severity. Or, in the case of apples, different compounds altogether may be at work.

``The association (of asthma risk) with apples suggests that we need a better understanding of how flavonoids, or other constituents of apples, influence respiratory health,'' Shaheen's team concludes.

As for selenium, they suggest that part of the blame for the UK's rising asthma rates may rest in the nation's declining selenium intake. The researchers note that selenium may protect against asthma by suppressing airway inflammation.

Selenium is found in foods such as enriched grains and pasta, Brazil nuts and walnuts, tuna and beef.

SOURCE: American Journal of Respiratory and Critical Care Medicine

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