I check my dictionary. Our bodies constantly regenerate new cells to replace old or disease cells. Some types of cells are being replaced very soon.
Bone cells have much longer life span before they are replaced by new cells.
It is estimated that after a certain time period. All cells composed of our whole bodies will be replaced at least once. Thus, we keep changing new bodies from youth to old age. To improve our health condition, we need to have proper nutrients to nourish our bodies. The speed of cells regeneration can be a good indicator of our health condition too.