DEAR DR. DONOHUE: I am a very active 75-year-old man. I have lifted weights and jogged since I was young. I am losing some of the muscle size I used to have. I have seen advertisements for DHEA that say it rejuvenates older people. Does this stuff work? – V.H.

DEAR DR. DONOHUE: I am trying to build my body, and I have read about DHEA. What’s your opinion on it? I am 23. – R.C.

ANSWER: DHEA – dehydroepiandrosterone – is a natural body substance that is converted into both the male hormone testosterone and the female hormone estrogen. Its production begins to wane in the 20s, so it has been suggested that taking it at older ages could bring back youthful vigor.

At younger ages, it has been touted as a muscle-builder. Commercial DHEA is derived from yams.

DHEA is not regulated as a drug. It is considered a supplement, so it does not come under the purview of the Food and Drug Administration. Its use, however, has been banned by a number of athletic organizations like the International Olympic Committee, the National Collegiate Athletic Association and the National Football League.

For R.C., I haven’t seen any reports that it benefits young people.

In one study, it increased bone density in older men and women. In another study, it enhanced older men’s libido. And in a third study, it decreased the amount of abdominal fat in both men and women. It might enhance muscle-building in the elderly.

All of these studies were done with small numbers of people, and the results are preliminary.

Possible side effects in women include the loss of scalp hair, the growth of facial hair and acne.

It might have deleterious effects on the liver. Its effect on the prostate gland and prostate cancer is not clearly defined.

I can’t endorse or condemn DHEA. I am waiting for more evidence to make up my mind.

DEAR DR. DONOHUE: I have a 15-pound barbell. Is there any exercise using this barbell that will build up my pecs? If so, how? – R.E.

ANSWER: The “pecs” are the pectoral muscles – the chest muscles.

The standard bench press is an excellent chest-muscle-builder. The exerciser lies on a bench with knees bent at the end of the bench and the feet on the floor.

Grasp the barbell with hands shoulder-width apart. Exhale while raising the barbell off the chest. Inhale when lowering it slowly back to the chest.

Perform three sets of eight consecutive lifts with a short rest between sets. If you can’t lift 15 pounds that many times, use a lighter weight. When you can do three sets of 12 consecutive lifts, increase the weight of the barbell.

By moving your hands closer together on the barbell, you exercise the inner pectoral muscles more – the part of the muscle toward the center of the chest.

By moving your hands farther apart, you put greater emphasis on the outer pectoral muscles.

You don’t need a barbell for pectoral-muscle development. The push-up, a favorite Army exercise, is a good pectoral exercise. Body weight serves as a natural barbell.

DEAR DR. DONOHUE: I am a 60-year-old woman who jogs. You said that early-morning heart attacks occur because the blood is thicker then. I drink water before I run, but after a mile of running my saliva thickens so much that I can barely swallow it. Does this mean my blood is thickening too? – S.S.

ANSWER: It means your mouth is drying out because you’re breathing through it – something most runners do. It’s not a sign that your blood is thickening.

Heart attacks occur more in the morning hours because blood platelets are at their stickiest then. They are more apt to clump and cause an obstruction in blood flow. At least, that’s one reason why heart-attack rates are higher in the morning.

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.