Women who eat plenty of tomatoes, carrots and leafy greens appear less likely to have asthma, researchers have found.
Though it’s uncertain whether the foods are the reason, the findings suggest that some vegetables may protect against adulthood asthma, the researchers report in the medical journal Thorax.
A number of studies have suggested that antioxidants or certain other nutrients in plant foods may help prevent or ameliorate asthma and other allergic conditions. Carrots, tomato juice and spinach contain nutrients called carotenoids, some of which are converted into vitamin A in the body.
Among other jobs, vitamin A helps regulate the immune system and maintain the lining of the respiratory tract.
In general, experts recommend that people eat at least five servings of fruits and vegetables per day for overall health. However, the authors of the new study write, “it is important to know which fruit and vegetables might be more likely to prevent specific diseases.”
To investigate which foods may sway asthma risk, they analyzed data on nearly 69,000 French women who were surveyed about diet and other health factors. Overall, 3 percent reported having asthma, with women who ate the most carrots, tomatoes and leafy vegetables being less likely to have the lung disease.
Dr. Isabelle Romieu of the National Institute of Public Health in Cuernavaca, Mexico, led the study.
Among the women surveyed, those who reported the highest intake of leafy greens - mostly spinach and lettuce - were 22 percent less likely to say they had asthma than women with the lowest intakes. Similarly, carrot lovers had a 20 percent lower risk of the disease, while tomato fans had an 18 percent lower risk.
The lower risks were seen even with other major factors - like weight, overall calorie intake, smoking and vitamin use - taken into account.
However, the researchers point out, they cannot rule out the possibility that higher intakes of carrots, tomatoes and leafy greens are simply a sign of a generally healthier diet - and not a special effect of these foods specifically.
Further studies, they conclude, are needed to confirm these results and to explore the possible effect of fruits and vegetables on asthma severity.
SOURCE: Thorax, March 2006.
Revision date: June 18, 2011
Last revised: by Sebastian Scheller, MD, ScD