DEAR DR. DONOHUE: Why have I lost so much weight? I dropped from 190 pounds to 165. I worked out three or four times a week, and I took three amino acids. Could the amino acids have caused the weight loss? Don’t they build muscle?

A good friend of mine told me that lifting weights at my age – 70 – would deteriorate my muscles. Is this true?

ANSWER: I had to edit your letter because yours is a complicated story. I can answer only some of your questions.

Amino acids are relatively small compounds that, when hooked together, make proteins. Amino acid supplements have been popular with athletes and weightlifters because muscles are proteins. For muscle growth, protein synthesis has to surpass muscle breakdown. Exercise breaks down muscles, and immediately after a strenuous exercise session, the amino acid content of blood is low. Taking amino acids, especially after exercise, therefore, should spur muscle growth. There is some truth to this. It’s particularly applicable to athletes and bodybuilders. For the rest of us, we get more than enough protein in our diets, and supplements are generally unnecessary. They do not cause weight loss.

Unintended weight loss is a warning sign that must be heeded. It occurs only when energy expenditure exceeds the calories available to the body. If you were eating as you usually do and you still lost weight, something is seriously amiss. Cancer is the most feared cause of unintentional weight loss, but there are many other possibilities: an overactive thyroid gland, a digestive tract that can’t absorb nutrients, hidden infections, depression and other serious illnesses. A doctor has to do an exhaustive search to turn up the answer to this puzzle.

Weightlifting at advanced ages, even in the 90s, is encouraged. It doesn’t deteriorate muscles; it builds them. Granted, at older ages, muscle growth isn’t as rapid or as impressive as it is in youth, but muscles still grow. Furthermore, weightlifting builds strong bones.

DEAR DR. DONOHUE: What do you think of caffeine before exercise? I hear that it improves endurance and enhances strength. If that’s the case, I want to try it. How much do I take? Can I take it in pill form? I don’t like coffee. – J.A.

ANSWER: Caffeine enjoys a reputation of improving athletic performance and prolonging endurance. Many studies have backed up those claims.

However, the studies vary considerably in the dose of caffeine used, and in the results obtained from using it. Not all are favorable.

At one time, the International Olympic Committee banned caffeine. It no longer does. The National Collegiate Athletic Association requires athletes to have less than a certain amount of caffeine in the urine in order to be eligible to participate in sports events it sanctions. Athletes should be aware of any rules on caffeine in their particular sports.

Two hundred milligrams of caffeine increases upper-body strength a bit. One cup of coffee has 135 milligrams. This 200 mg amount is slightly less than two cups of coffee. That’s the amount you should experiment with. You can take caffeine in tablet form if you want, or get it from other drinks that contain it. The scientific studies done on caffeine usually use tablets.

DEAR DR. DONOHUE: I saw on TV that exercising late in the evening or at night is harmful to the heart. Is it? – A.D.

ANSWER: I can’t find any evidence that backs up such a statement. People can exercise at the time that’s most convenient for them. At one time, caution was urged for early-morning exercisers because it was believed that more heart attacks occurred at that time. That information has been challenged.

DEAR DR. DONOHUE: I am an 84-year-old woman and had been doing quite well. About 40 years ago, a heart doctor told me I had a defective heart valve but that nothing needed to be done about it. My current doctor decided I need to see a heart specialist now. The heart doctor said I need medicine to take the pressure off my heart. For the past two months, I have taken Coreg and another medicine. (I also take Norvasc and Dyazide.) Since I began the new medicines, I feel lightheaded and can’t walk as I used to. I am exhausted all the time. I don’t feel like getting out of bed. I would like your opinion. – J.E.

ANSWER: The heart doctor judged that you need medicine to keep your heart pumping well in the face of a defective heart valve. I wonder if the doctor knows you are taking your other medicines. I believe that your current symptoms come from taking too much medicine.

Dyazide is a diuretic – a water pill. It takes fluid out of the body and lowers blood pressure. Actually, it’s a combination of two water pills. The second water pill keeps potassium in the body. The first water pill can lead to potassium depletion. So this pill keeps you in potassium balance.

Norvasc (amlodipine) is a calcium-channel blocker. It, too, lowers blood pressure, but it does so differently from the water pills’ action.

Coreg, your new medicine, is a beta blocker. It also brings down blood pressure and slows the heart.

I am sorry, but I couldn’t read what your fourth medicine is. It doesn’t matter. Your symptoms of fatigue and lightheadedness could well be caused by too low a blood pressure from all your medicines. I understand the heart doctor’s choice of medicines. They’re the medicines that are often used to help the heart beat with less strain in the face of a defective heart valve. But the combination is most likely bringing your pressure to too low a level. Talk to your heart doctor as soon as possible. A call will do.

The booklet on heart valve disorders covers this topic in depth. Readers can order a copy by writing: Dr. Donohue – No. 105, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6.75 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

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