Jolanta Dorszewska and Wojciech Kozubski

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http://dx.doi.org/10.5772/intechopen.70214

**1. Introduction**

In humans, the threshold of normal aging is accepted to involve the age of 60 years. At the same time, the age above the normal aging was divided into three subgroups, including young olds (65–75 years of age), old olds (75–85 years), and eldest olds (above 85 years of age) [1]. Normal aging is defined as weakening of the repair and defense processes of the body. The weakening of the defense in aging organism leads to increase in the level of toxic factors such as reactive oxygen species (ROS), calcium ions, and immuneinflammatory response. The consequence of the change in the level of these molecular factors is the development of age-related diseases, among others, atherosclerosis, tumors and neurodegenerative diseases. Simultaneously, ROS may lead to the damage of macromolecular compounds, such as lipids, proteins, and DNA [2, 3]. ROS may also play an important role in the modulation of transcription factors activation, gene expression, and various life processes of a cell.
