By definition, a stem cell is an undifferentiated cell with the potential of forming any specialized cell in the body or even more stem cells. Theoretically, it means one stem cell has the potential to create a whole organism, which only occurs under optimal conditions. Knowledge about stem cells has exploded over the last two decades since I first encountered it in grad school. They now know there are two major types of stem cells: embryonic stem cells and adult stem cells, which are also called tissue stem cells.
Apart from having the ability to form an organism, scientists also discovered the amazing feature of adult stem cells capable of replacing aging, injured and diseased tissue. This is an ongoing process since birth. It became apparent, that just as important as it is to have healthy cells, we need healthy stem cells to combat the effects of aging as well as disease. If these stem cells are damaged, they will stimulate the growth of more damaged cells such as the infamous cancerous cells.
Scientists and physicians now have a great interest in the development of therapies for replacing defective or damaged cells resulting from a variety of illnesses and injuries with the use of stem cells. In some parts of the world, it is becoming common practice to treat some conditions with stem cells injected into the body. A great example is the treatment of inflamed joints due to arthritis with the local injection of a patient’s own stem cells drawn from the blood. The same treatment is available for bone loss in the jaw. There are also treatments available for permanent damage to certain tissues such as neurons, which on its own, will take very long to heal and recover. Most of these treatments are still in the experimental stage and costs thousands of dollars to have access to it.
The good news to us is that we do not have to wait for scientists to figure everything out before we could reap the benefits of stem cells. The latter of which, contrary to the belief as recently as 20 years ago, are found all over the human body. Initially, when stem cells were discovered, the idea was created that it had to be harvested from embryonic cells and then transplanted to an individual. This was problematic and unethical as it called for the embryos to be sacrificed. As more and more sources of stem cells were discovered, researchers learned that we continuously make stem cells to renew our bodies. Although we do not yet have all the facts on the table, we know enough to benefit from current knowledge in our quest to live healthier and age less painfully.
We know the following from the research:
1. Fasting stimulates the function of stem cells. 
2. Stem cells become active when fat metabolism is stimulated, but not when we overconsume very high amounts of fat – a diet that has not been very well defined yet. This means that the body has to be in fat burning mode where it uses its own fat stores. 
3. Glucose over consumption suppresses stem cells function and maintain the deterioration of aging cells. 
4. Breast milk is a source of stem cells which can form a wide variety of cells in the infant’s body. 
5. Resveratrol, selenium, and spirulina were found to enhance stem cell production and function. This does not mean that these are the only nutrients to do that. Because research on stem cells is still relatively new and incomplete, we could assume that other nutrients from plants would do the same. [4-6]
6. Exercise in general, and even at low intensities such as tai chi, increases the number of stem cells in the body. [7, 8,9]
7. According to researchers in London, England, alcohol also damages stem cells. The most profound example of this is most probably the children born from alcoholic mothers who suffer from fetal alcohol syndrome.
8. BPA in plastics causes cancerous stem cells to proliferate.
9. Radiation kills of stem cells. We mainly think of sun damage, but exposure to medical tests such as x-rays, CT scans, and mammograms should also be used with greater care as it too damages stem cells.
So, to conclude, it looks as if it is again, a matter of lifestyle. While stem cell research is far from complete, in broad strokes, these would be my recommendations on how one could optimize the stem cells in the body. After all, they are up for the grabs.
Babies should preferably be breastfed.
Eat a variety of plant-based material, and do so in abundance.
Do not overconsume fat, but make sure your body can consume fat. That is achieved by cutting out all refined sugars in the diet. Your measurement for this would be your waistline. If you need to lose weight, incorporate occasional fasting to help boost your efforts.
Use alcohol only occasionally.
Avoid the use of plastic containers as much as possible. Try to get better at this all the time. We will not only thrive as humans but also help clean up our environment.
Avoid all sorts of radiation, including sun exposure and medical testing such as X-rays and CT scans. Negotiate fewer tests or safer tests with your doctor.