In our body there is a continuous metabolism. Some substances come with food, others are destroyed, oxidized and removed from the body. In different organs, metabolism occurs at different intensities. So, by the end of the month, not a single atom of those that made it up at the beginning remains in the liver; all of them are replaced by new ones. So calculate how many times the liver has been updated over the years you lived. These processes occur in every cell, nutrients, oxygen, water, mineral salts, vitamins enter the cell. Some of these substances are used for growth and development, and some of the organic substances are used for biological oxidation and energy for muscle work, maintaining body temperature, creating new substances, conducting nerve signals.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.