Q. I know that cells in the body regularly replace themselves by multiplying and dividing and that this happens in the brain, too. So how does the brain retain memories?
A. Excellent question. Yes, body cells are able to multiply and divide on a fairly regular basis although the quality of the new cells may diminish with very old age. There are various reports of how often the body generates new cells but this is a range reported by some:
- Heart muscle cells: ongoing renewal
- Joint and cartilage cells: ongoing renewal
- Bones/skeleton: 10% annually
- Colon cells: 2-3 days
- Stomach cells: 2-9 days
- Blood platelets: 10 days
- Taste bud cells: 10-14 days
- Lung cells: 14-21 days
- Red blood cells: 4 months
- Liver cells: 5 months
It appears to be a different story with neurons, the brain’s thinking cells. Some research suggested that the brain’s search engine—the hippocampus—was capable of birthing new cells. More recently that conclusion has come into question and is less clear. Some research also suggests that the glial cells that support and nurture neurons, are capable of replacing themselves.
At time of birth and for some time afterward, the brain contains more neurons than it will retain for adulthood. During the first few years the brain goes through a process of pruning and gets rid of neurons that are not being used, which underscores the importance of stimulating the brain and giving it healthy and active learning experiences to notify the brain that these cells are being used and needed. You may have heard recommendations that beginning during pregnancy it can be important to “talk to the fetus aloud,” read to it, play music for it, and so on. After the baby is born, recommendations continue to be: talk, talk, talk, sing, laugh, read aloud...and so on.
Consensus is that by and large at some point in early life you will have all the brain cells that likely will be generated and after that learning involves growing more connections between cells. Therefore, from this perspective, the brain remembers as long as it is healthy and well because it is using the same cells.
Again, this points out the criticality of taking very good care of those cells: safety protection, plenty of water so the tissue doesn’t shrink, quality nutrition, sufficient sleep, physical activity every day, challenging mental stimulation every day, And that is precisely the reason for the Longevity Lifestyle Matters program.