Diet and Asthma
Carotenoids are oil-soluble plant pigments that the body can convert to vitamin A. They are responsible for the bright colors of produce. The best known carotenoid is beta-carotene. Beta carotene also has the most vitamin A activity of all of the carotenoids. Other carotenoids include alpha carotene, lycopene, lutein, astaxanthin, beta crpytoxanthin, and zeaxanthin.
A randomized, placebo-controlled study, published in the American Journal of Clinical Nutrition (2012 Sep; 96(3): 534-43), looked at dietary intake in 137 adults with asthma. For two weeks the subjects were given meals that were high in antioxidants (five servings of vegetables and two servings of fruit each day) or low in antioxidants (less than two servings of vegetables and one fruit each day). The subjects who consumed the low antioxidant diets were given a supplement containing a tomato extract with 45 mg of lycopene (a carotenoid). or a placebo.
At the end of the two weeks, the group receiving the high-antioxidant diet had measurably better breathing capacity (as measured by forced expiratory volume and percentage predicted forced vital capacity). Those eating the diet low in antioxidants had an increase in C-reactive protein (a substance that increases with inflammation and is used as an indicator of inflammation). Lycopene supplementation in the low antioxidant group did not improve breathing or reduction in inflammation. Where the diet high in carotenoids improved function in asthmatics, supplementation with carotenoids did not.