Teenagers who don't eat enough fruit or take sufficient vitamin E and omega 3 fats are more likely to develop asthma, according to research from the Harvard School of Public Health.

The study, involving 2,112 US and Canadian students, looked at the relationship between dietary habits, lung function and respiratory symptoms.

Results showed that at least a third of the teens' diets were below the daily recommendations for fruit, vegetables, vitamins A and E and omega 3 fats, which led to decreased lung function and an increased risk of wheezing and asthma, particularly among those who smoked.