Compounds that inhibit oxidation are called antioxidants. Oxidation can produce free radicals and lead to chain reactions, which damage healthy cells. To prevent this from occurring, animals and plants maintain complex systems of overlapping antioxidants, such as vitamin C and E, glutathione and enzymes. Antioxidants are classified as hydrophilic and lipophilic. These may be synthesized in the body or obtained from diet. A certain proportion of antioxidant vitamins are needed in the diet for good health. However, the proportion and the antioxidant species with positive health effects are still debated. Research is being undertaken to investigate the potential effects of dietary antioxidants on neurodegenerative diseases, such as Parkinson's diseases, amyotrophic lateral sclerosis and Alzheimer's disease. This book is compiled in such a manner, that it will provide in-depth knowledge about the importance of antioxidants in health and disease. Different approaches, evaluations, methodologies and advanced studies on antioxidants have been included herein. A number of latest researches have been included to keep the readers up-to-date with the global concepts in this area of study.