Dietary supplements are regulated to some extent but not as strictly as medications.Some products are advertised to have health benefits but have no clinical trials demonstrating safety or effectiveness.The consumption of some dietary supplements may also help prevent cancer. A number of essential vitamins, including vitamins A, C and E, act as antioxidants in the body. They work to neutralize chemicals called free radicals that cause oxidative damage within your cells. Dietary supplements, which are not registered , are marketed as a solution or preventative measure for a number of disorders, or to supplement nutrients lacking in your diet. To safely reap the benefits of taking dietary supplements, always consult with a physician before taking any supplement to help avoid negative side effects.