Antioxidants, as the word means, are substances, which prevent the oxidation of other molecules. Oxidation is a chemical reaction, by which free radicals are produced. Free radicals in turn are able to start a chain of reactions, which can damage or cause death to the cells. Through this process, cell is under oxidative stress, which can change the cell’s structure or functions. Because of these changes, oxidation stress seems to be responsible for many human diseases, including cancer.
Of course, oxidation is something which happens naturally, although the modern way of life has increased a lot the oxidation agents, something that affects the health of modern people. By adopting a nutrition highly concentrated in antioxidants, you literally create a natural shield against oxidation. Moreover, foods with many antioxidants are usually tasteful with a pleasant flavor. Many of the antioxidants, such as flavonoids, are substances responsible for the food’s smell, the taste and the color.
There are many nutrients that act as antioxidants. Vitamin C, vitamin E and β-carotene are excessively studied for their antioxidant action. Vitamin C is the most important water-soluble antioxidant in extracellular fluids. Vitamin C helps to neutralise reactive oxygen species (ROS) in the water or aqueous phase. Vitamin E is the most important lipid soluble antioxidant. It is important as the chain-breaking antioxidant factor within the cell membrane. It can protect the membrane fatty acids from lipid peroxidation. Vitamin C in addition is capable of regenerating vitamin E, so there is a direct link between them. β-carotene and other carotenoids also have antioxidant properties. Furthermore, carotenoids work in synergy with vitamin E.
Apart from natural sources, the human body has also some antioxidant mechanisms that can protect itself from ROS. There are enzymes such as, glutathione peroxidase, catalase, and superoxide dismutase (SOD), which do this work. The consumption of micronutrient cofactors such as selenium, iron, copper, zinc and manganese, is essential for their activity.
Picture 1. Content of antioxidants per food. (Source:www.nature.com)