The birth and death of cells is a natural process found in multi-cellular organisms. This cycle has a key impact on the progression of disease and how we age. But it is not as simple as all our cells refreshing at once, creating a virtually new body. Each cell in the body has its own distinct lifespan. Take, for example, the lining of the stomach, being constantly battered by stomach acid means the cells here are renewed every few days. However, it is not like this for all parts of the body, with other cells having a much longer lifespan.

Whilst is it a popular idea that all the cells in the body are renewed at least every 7 years, this isn’t strictly true. Whilst many cells are indeed refreshed every 7 years, or more frequently, this is not how it works for all cells. Cells residing in the skin and gut are some of those that are refreshed frequently. This does mean that the cells making up your skin today are different from those making it up 7 years ago. However, if we are to look at the heart, this is an organ that renews at a slow rate, with only 40% of the cells here being renewed. In terms of the skeleton, it is around 10 years for renewal. Brain cells also renew, but not at a particularly fast rate. Here, there are certain types of neurons that remain with you for your whole life. Some of the cell populations can rejuvenate, but they are not replaced completely, only somewhat over your lifetime.

Of course, when the lifespan of cells is studied, we cannot be certain that our conclusions can be exactly correct, as it is feasible that cells behave differently outside of the body than they do inside it. Whilst there is a considerable amount of research into this particular area, it is still unclear what factors are responsible for cell birth and death rates.

Some recent research is particularly interesting, with observations showing that across species, for a specific cell type, cell lifespan and cell replicative capacity have been shown to correlate strongly with body size and lifespan in mammals.

One of the parts of our body which remains the same from birth to death, never being renewed is our DNA. DNA remains the same from the day of a cell’s birth and throughout its lifespan. When a cell divides, the DNA incorporated into the new cell contains a certain amount of carbon-14 in it’s DNA. Previously, body tissue renewal has been studied by looking at the radioactive material carbon-14. Carbon-14 makes up a part of our DNA, gained from when we eat plants.

Life expectancies of cells:

  • The cells making up bones take around 10 years to renew. As we age, the renewal process slows down.
  • The liver renews every 150 to 500 days. This organ detoxifies the body and deals with a wide range of contaminants.
  • The hair has a life span of 6 years for women and 3 years for men.
  • Cells of the skin renew every 2 to 4 weeks as they face wear and tear.
  • Cells of the stomach and intestines last only around 5 days.

Taking into account the different lifespans of each type of cell, on average, our cells renew every 7 years. Yet, some of our cells have a lifespan of days, whilst others last a lifetime. Take the cornea, cells here renew in as little as a day. Yet the neurons in our brain can stay with us until death. Understanding these variations in cell lifespan enhances our comprehension of health and longevity mechanisms.