Beta carotene is plentiful in vegetables and fruits, and is beneficial in this form. The 600 carotenoids are important for health and are found in yellow, red, and deep green vegetables and fruits. Beta carotene provides a good lesson, especially because it was a star among supplements. Then came two first-rate studies showing that beta carotene supplements could cause serious harm, at least in smokers. Since then, scientists have been trying to explain what went wrong with beta carotene, and recently some interesting theories have emerged.
Plants are vital sources of antioxidants for humans and other animals.
In addition, hundreds of dietary supplements now trumpet the antioxidants they contain. There are many types of antioxidants, and they do different kinds of work. What marketers of supplements never tell you is that not all of it is good work. That's what the two beta carotene studies showed. The other study, a large Finnish one published two years earlier, yielded similar results.