Q. Is it really true that body organs are replaced regularly? And what about the brain?

A. Most cells in the body are replaced regularly so eventually a body organ, such as the heart, likely has every cell replaced over time. This is become some die due to age or wear and tear; some reach the end of their life cycle. Current wisdom is that neurons are not replaced in the adult human brain with the exception of the hippocampus, the brain’s “search engine,” so to speak. The birth of new neurons has been confirmed in the hippocampus in the adult brain and may continue until the 5th decade of life.

The hippocampus is also linked with the creation of new episodic memories. According to Margaret Reece, PhD, the formation of episodic memory is very complicated and may over-write older memories. Often new episodic memories incorporate parts of old memories. For example, if you revisit your old school for a reunion, memory of the reunion will incorporate earlier events from the past when you attended classes at the school. 

Following are estimated averages for cell replacement in the human body.

• Stomach - new every 2-9 days
• Taste buds every 10-14 days
• Lungs - every 2-3 weeks
• Colon - every 2-3 days
• Skin - in 14 days or less
• Red blood cells - every 4 months
• Bones - every 10 years
• Heart - ongoing resulting in a new heart every 20 years)
• Blood Platelets - every 10 years
• Liver - every five months
• Joints and cartilage cells - constantly renewing

Because of this, changing to a healthier habit can have a positive impact on cell replacement in sometimes only a few days.