Beta-Carotene is a member of a larger family of antioxidant nutrients called “carotenoids”, which are natural pigments found in plants, where they play a critical role in the photosynthesis process. The best source of beta carotene is carrots, though it is also found in green leafy vegetables and fruit.
Beta-carotene supplements come in softgel capsules and as bulk powder.
"A few small clinical trials suggest that specific antioxidants from diet or vitamin supplements might improve asthma control or lung function in asthmatic children or adults."
Some studies have found that oxygen free radicals have a causal role in auto-immune diseases, such as rheumatoid arthritis (RA).
However, a report by the Harvard School of Public Health, found that "Randomized, placebo-controlled trials—which, when performed well, provide the strongest evidence—offer little support that taking vitamin C, vitamin E, beta-carotene, or other single antioxidants provides substantial protection against heart disease, cancer, or other chronic conditions. The results of the largest such trials have been mostly negative."