What are stem cells, and why does the body keep making them
Stem cells are unspecialized cells with two defining abilities: they can copy themselves and they can turn into other cell types. They are the reason skin heals, blood replenishes, and tissue quietly repairs itself every day.
This article explains general cell biology. It makes no claim that any food, berry or product changes the number or behavior of a reader's stem cells.
The short answer
A stem cell is a cell that has not yet picked a final job. It has two defining abilities: it can divide to make more of itself, called self-renewal, and it can turn into a more specialized cell type when the body needs one, called differentiation. Together those two properties make stem cells the body's built-in repair and renewal system.
The two properties that make a cell a "stem cell"
Most of the cells doing work in your body right now have already specialized. A skin cell is a skin cell for the rest of its life. A red blood cell carries oxygen and nothing else. Stem cells are different because they have not committed to a single identity yet, and biologists define them by exactly two abilities working together.
The first is self-renewal, the capacity to divide and produce more stem cells, keeping the pool from running out. The second is differentiation, the capacity to turn into a specialized cell type, such as a muscle cell, a blood cell or a skin cell, once the body signals that one is needed. A cell needs both properties to count as a stem cell. A cell that can only copy itself, or only specialize once and never again, does not qualify.
Not all stem cells can become the same things
Stem cells are often lumped together in casual conversation, but researchers separate them by how much they can become.
- Embryonic stem cells are the most flexible, capable of becoming almost any cell type in the body. They exist only in early development.
- Adult, or somatic, stem cells live in specific tissues throughout adulthood, such as bone marrow, the gut lining and hair follicles. They are more limited, usually able to become only the cell types found in that tissue.
- Induced pluripotent stem cells (iPSCs) are ordinary adult cells that researchers reprogram in a laboratory to behave like embryonic stem cells. This 2006 to 2007 breakthrough, credited to Shinya Yamanaka, opened a path to study pluripotent cells without using embryos.
What stem cells actually do, day to day
The clearest way to understand stem cells is to look at what happens without them. The lining of the human gut replaces itself roughly every few days. Skin sheds and rebuilds constantly. Blood cells, which have a limited lifespan, are restocked from stem cells living in bone marrow. None of this is a response to illness. It is ordinary maintenance, running quietly for as long as a person is alive.
Key takeaways
Stem cells, in three points
- Two defining traits. A stem cell must be able to self-renew and to differentiate into other cell types.
- Not all stem cells are equal. Embryonic, adult and lab-induced pluripotent stem cells differ in how much they can become.
- They run in the background. Ordinary tissue turnover, skin, gut lining, blood, depends on stem cell activity every day, not only after injury or illness.
Where this series is going
The rest of this science series looks at how circulating stem cell activity tends to change with age, and at a specific 2019 human study that measured a rapid shift in circulating stem cell markers after a sea buckthorn berry extract. Start with why stem cells decline as you age, then read the flagship piece on what the 2019 sea buckthorn study found.
From the journal shelf
Sea Buckthorn Puree
A whole-food sea buckthorn puree with 190+ naturally occurring compounds, omega 3-6-7-9, 201 mg vitamin C per serving and 0 g added sugar. It is a nutritional food, not a supplement, and not the same as the isolated berry extract studied in the research discussed above.
- 190+ compounds
- Omega 3-6-7-9
- 201 mg vitamin C
- 0 g sugar
Educational content only. This product is not studied for, and does not claim to affect, stem cell counts.
What is a stem cell in simple terms?
A stem cell is an unspecialized cell that can still become other, more specialized cell types and can also make copies of itself. Most cells in the body have already picked a job, such as being a skin cell or a muscle cell, and cannot change course. A stem cell has not committed yet, which is what makes it useful for repair and renewal.
What two properties define a stem cell?
Self-renewal and differentiation. Self-renewal means a stem cell can divide and produce more stem cells, keeping the supply going. Differentiation means it can also turn into a specialized cell type when the body needs one. A cell must be able to do both to be classified as a stem cell.
Where are stem cells found in an adult body?
Adults carry stem cells in specific reservoirs, including bone marrow, the lining of the gut, hair follicles, and in small numbers circulating in the bloodstream. These are called adult or somatic stem cells, and their job is narrower than embryonic stem cells, typically limited to renewing the tissue they live in.
Are all stem cells the same?
No. Embryonic stem cells can become almost any cell type in the body. Adult stem cells are more limited, usually only able to become the cell types found in the tissue where they reside. Researchers also study induced pluripotent stem cells, ordinary adult cells reprogrammed in a lab to behave like embryonic ones.
Why do stem cells matter for everyday health?
Stem cells are the reason skin heals after a cut, the gut lining replaces itself every few days, and blood cells are continuously restocked. They are a background maintenance system running for as long as a person is alive, not a rare or exotic feature reserved for illness or injury.
This article is educational content, not medical advice. It does not diagnose, treat, cure or prevent any disease. Speak with a qualified healthcare provider about your own health decisions.
