DEAR DR. DONOHUE: Please identify stem cells. I do not understand their pros and cons. – H.D.

DEAR DR. DONOHUE: Why, in a free country, are stem-cell implants outlawed? – J.M.

ANSWER: Stem cells are cells with the potential to develop into one or more of the body’s 220 different cell types – bone, liver, spinal cord, heart muscle and so on. Stem cells derived from embryos have the greatest potential to do this. That potential is called “plasticity.” Adults make stem cells, but adult stem cells are not abundant, and they don’t have the great plasticity of embryonic stem cells – at least, that appears to be the case. Another source of stem cells is the umbilical cord. Umbilical-cord stem cells are easier to collect than adult stem cell, are less likely to provoke an immune response in the recipient, and seem to have the capacity to morph into a greater variety of body cells than do adult stem cells.

Illnesses and conditions that might benefit from stem-cell treatment include diabetes, Alzheimer’s disease, spinal-cord trauma, heart attacks and Parkinson’s disease. This is only a partial list. The promise stem cells offer for medical breakthroughs is breathtaking.

We live in a democratic society where there is a diversity of moral beliefs. That’s where the controversy over the use of embryonic stem cells arises. Some consider the destruction of an embryo for its stem cells to be an unconscionable act.

Stem-cell research and stem-cell therapy are not outlawed. At present, it is not permissible to use federal funds to support new embryonic stem-cell research. However, it is quite legal to carry on research on embryonic stem cells with private funds. There are no federal limitations on research with adult or umbilical-cord stem cells.

For clarification, the embryonic stage is the first eight weeks of development. Embryonic stem cells are taken from very young embryos.

DEAR DR. DONOHUE: I have developed a foot odor that can’t be washed away. I soak my feet every night. I have never had this before. Why now? – R.L.

ANSWER: The feet have more than 250,000 sweat glands that can put out up to half a pint of sweat daily. Damp feet, encased in shoes and socks that keep them warm, provide a perfect breeding ground for bacteria that emit offensive odors. I can’t tell you why this happened to you now, but take a look at your soles. If you see tiny pits on the heels, the balls of the feet and the bottoms of the toes, then you could have a condition called pitted keratolysis, caused by a bacterium that can be acquired at any stage in life. This bacterium gives rise to a most disagreeable smell and for cure requires an antibiotic ointment such as clindamycin.

If you don’t see any pits, then you have to go on a program to keep your feet dry to eliminate the more common bacterial causes of bad-smelling feet. Bathe the feet twice a day in warm water and wash with a mild soap. Then thoroughly dry them. Careful use of a blow-dryer assures that all moisture is gone. Then spray the soles with an antiperspirant. Go shoeless and sockless as much as possible or wear sandals.

If ordinary antiperspirants don’t keep the feet dry, prescription ones with a high concentration of aluminum chloride can usually stop sweating. One brand name is Drysol.

When wearing socks, change them twice a day. Don’t wear the same shoes two consecutive days.

DEAR DR. DONOHUE: For some years I have been taking Fosamax for osteoporosis. Now I have been told to stop. Is it because I have taken it for five years? – C.B.

ANSWER: Fosamax (alendronate) and related drugs are among the most effective osteoporosis medicines. A recent study showed that women who took this medicine for 10 years had an increase in bone strength throughout the entire 10 years. That’s the longest study, to date, for the use of Fosamax. A smaller study, involving only nine women on long-term Fosamax, showed poor fracture healing in four of those women. An editorial comment suggested five years might be an appropriate cutoff for therapy.

DEAR DR. DONOHUE: I am a 79-year-old man in good health. I play tennis five times a week. In the past three months, veins in my lower left leg have become raised. A doctor told me they are varicose veins and not to worry about them. There is no pain involved. I thought varicose veins were always knotted. What causes them, and what should I do about them? – G.

ANSWER: Varicose veins are dilated, enlarged veins. They’re often gnarled and ropey-looking, but they can be smooth.

Defective vein valves cause them. In leg veins (and all veins), when blood flows through, valves close to keep the blood flowing in an upward direction back to the heart. When the valves are incompetent, blood stagnates in the veins and stretches them out of shape – varicose veins.

Heredity is a big factor in people’s incompetent leg vein valves and varicose veins. Obesity promotes them. Prolonged standing without moving is another factor. Women who have had children are prone to getting them, because a pregnant uterus impedes blood return from the legs.

You can keep your veins from enlarging by wearing elastic compression stockings. Elevate your legs when you sit, and the higher you elevate them, the better. Exercise is usually helpful and not harmful, because the contracting leg muscles pump blood out of leg veins.

The impact of feet on a hard surface might not be the best for varicose veins, but the impact can be softened by wearing well-padded, shock-absorbing shoes. Keep on with your tennis.

If the veins aren’t causing trouble – aching legs or swollen ankles – you can let them lie as you would a sleeping dog.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.