consumption of fresh fruit, vegetables and fish, rather than consumption of vitamin supplements, will be beneficial in helping to protect against airway disease

It may be that improving the diet, by increasing the consumption of fresh fruit, vegetables and fish, rather than consumption of vitamin supplements, will be beneficial in helping to protect against airway disease.

The above is extracted from the conclusion of 

http://m.erj.ersjournals.com/content/21/4/664.long