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Soy isoflavone supplements of no benefit in patients with poorly controlled asthma

A randomised clinical trial has found soy isoflavone supplements are not beneficial to people with poorly controlled asthma.

Dietary factors are associated with asthma prevalence and severity, and previous studies have suggested supplementation with soy isoflavone may be an effective treatment for patients with poor disease control.

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To investigate, researchers conducted a randomised, double-blind, placebo-controlled trial between May 2010 and August 2012 at 19 adult and paediatric pulmonary and allergy centres in a United States clinical research network. A total of 386 adults and children aged 12 years or older were randomly assigned to receive soy isoflavone supplement containing 100mg of total isoflavone (n =193) or matching placebo (n =193) administered in two daily doses for 24 weeks.

The results showed that, compared with placebo, use of soy isoflavone supplement did not result in improved lung function or clinical outcomes, including symptoms, episodes of poor asthma control, or systemic or airway inflammation. The authors conclude that the supplement should not be used for patients with poorly controlled asthma.

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