Root Cause of Aging
If cells are replaced on a regular basis, why do we age? Because there’s something in the environment that messes with this equilibrium, and throws off the mix. If the equilibrium of cells is disturbed, you may still be a teenaged boy, but you’ll likely get arthritis. If the equilibrium of cells is disturbed, your skin will age faster. If the equilibrium of cells is disturbed, you’ll develop cancer. If the equilibrium of cells is disturbed, the number of immune cells will be low, and your immune system won’t be able to keep pace with the pace of the tumor. If the equilibrium of cells is disturbed, growth rates will be stunted, and your body will likely die young.
The most plausible culprits for the disruption of the homeostatic equilibrium are chemical.
What Causes Aging?
Most of the cells in the human body are replaced at a rate of approximately 1,000 cells per second. For this reason, we can say that the average number of cell types in the human body is approximately constant. If we assume that the average number of cell types in the human body has remained relatively constant over time, then the number of total cells has increased by the square of the average number of cell types. When we extrapolate this increase to the other side of the age spectrum (cells not being replaced), the number of total cells should increase by about 1,000 per second.
Here are some things that could go wrong: All cells (including neurons and most cell types) are replaced at a rate that is independent of cell number (regardless of cell number).
How Do We Fight the Root Cause of Aging?
Think about how cells in our body maintain their homeostatic equilibrium. Without an adequate supply of nutrients (eg. insulin or iron), a cell gets damaged and bleeds over the course of a few hours or days. Blood vessels also carry nutrients to cells, which usually means that cells get damaged during the process (thanks for that, arteries!). Cell injury by nutrient deficiency is a major cause of cancer. Without adequate cellular defenses (like enzymes or the innate immune system), we all get cancer.
Theoretically, some method could regulate this natural cell turnover in all cells at all times, and keep our cells youthful and healthy. This means that the only reasonable solution to the root cause of aging is to rebuild those homeostatic equilibrium mechanisms in all cells at all times.
Conclusion
Numerous lines of evidence show that the rate of cell turnover of every type of tissue is carefully controlled in an overall “homeostatic equilibrium”. And even more clearly, this balance fluctuates with age.
Cell turnover in newborns is very low. This is often called “negative inotropic pressure”. However, the number of cellular components in the human body continues to increase, even during childhood, reaching a maximum in late adolescence and early adulthood.
Around the age of 40, the number of cells decreases rapidly. So too does the number of cell components, because cells have to be replaced every few weeks or months. You could say that it’s an unstable equilibrium; anything that happens can upset the balance, even something as innocuous as a birthday celebration.
