(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Hello, dear readers! Once again, you've filled our overflowing mailbox with questions, concerns and some kind words (thank you, as always, for those), so let's get right to business:

-- "I'm in my mid-50s and am having trouble sleeping. Melatonin was effective, but only for a short time. A friend suggested taking ibuprofen p.m.; it works very well, but I'm concerned about taking it on a daily basis. Is it safe to take each night?"

Pain relievers targeted for nighttime use can be helpful with sleep issues because many of them contain diphenhydramine, an antihistamine also called Benadryl. Drowsiness is one of the drug's side effects, which is why it's used in over-the-counter sleep aids. While it's a useful fix for the short-term, like for sleeping through a long flight, it's not a great long-term solution. If you want to use Benadryl, we recommend you opt for the sleep aid rather than the pain reliever, which contains medication you don't need.

However, the quality of sleep from Benadryl use is generally not very good. For our own patients, our preference for insomnia supplements is melatonin or magnesium. When supplements aren't effective, then we suggest the prescription medication trazodone.

-- "I've been hearing a lot about cherry complex, which is supposed to be good for you. But what's in it? What does it actually do?"

You're referring to a supplement derived from either the fruit or the bark of black cherries, which are believed to have antioxidant properties. According to some studies, antioxidants may be a hedge against inflammation, which plays a role in disease. Black cherry, also known as wild cherry, has long been an ingredient in herbal medicine and home remedies. In colonial times, it was used in cough syrups, as a sedative and for pain relief. The makers of various cherry complex products claim it is useful for cough, chest congestion and diarrhea. Due to certain chemical properties of wild cherry, however, it should not be used by women who are pregnant or breastfeeding. Those chemicals can also change the rate at which the liver breaks down certain medications. Due to a lack of studies into the use of wild cherry, dosage is basically guesswork. We recommend talking to your family doctor before using cherry complex to be sure it's right for you.

-- "When we perspire, do we lose sodium that we can (or perhaps should) then restore by taking in more sodium than we otherwise would? If so, how can we tell how much sodium we can safely add? Let's assume that our regular diet keeps us at an acceptable sodium level."

It's the job of our kidneys to regulate sodium and water balance, and when they're healthy, they do it extremely well. The sodium we lose when we sweat is replenished via the foods we eat. If for any reason there is either a deficiency or an excess of sodium, the kidneys will correct the imbalance. For most of us, the teaspoon or so of salt that we consume each day is adequate. Elite or endurance athletes may occasionally require more, but they are the exception.

Thank you again for your interest in the column. We'll be back with more letters next month.

Dear Doctor: I wonder, as a 67-year-old woman, whether my workout routine would be considered too strenuous? I walk six miles and use weight machines five days a week, and do an hour each of yoga, Zumba, cardio and stretching each week. This routine has helped me lose 27 pounds and get off of blood pressure medicine. Do you think I need to slow down?

Dear Reader: That's quite an impressive regimen for age 67! As long as you're in good health and enjoy what you're doing, we see no reason that you can't continue. That said, there are a few things for you to consider that can help you evaluate your exercise routine both now and in the future.

We have multiple goals when we exercise. On the physical side we want to increase muscle, decrease body fat, enhance agility, flexibility and coordination, and improve heart and lung function. (And for those of you lucky enough to be in peak physical shape, you exercise to maintain it.) However, thanks to the more-is-better mentality that can overtake any program of self-improvement, it is indeed possible to do too much. Gauging whether you fall into that category is a bit more complex than just deciding that a list of activities looks too long or daunting.

Our bodies and minds are not at all shy about letting us know when we're overdoing it. On the physical side, signs that you may want to ease up include being unable to continue to perform at the same level, persistent aches or pains, fatigue during and after exercise, loss of appetite, repeated injuries and increased susceptibility to colds. Mental effects can include poor or disrupted sleep, loss of interest or motivation, as well as anxiety, irritability or depression.

Because we're generally working to improve when we exercise, a certain amount of discomfort can be part of the process. But if a workout leaves you worn out to the point that you no longer feel the physical and emotional benefits or have lost the emotional afterglow that so often accompanies physical achievement, then it's time to reassess.

If you begin to experience any of the symptoms or side effects we just discussed, either physical or mental, then you should consider making some changes. You can cut back a little bit on frequency or intensity, include an additional day (or two) of rest or swap out an activity with variations that will help keep things fresh. Right now, you have included all three elements of a well-rounded exercise routine -- cardio, resistance and flexibility. If you do decide to make changes to your routine, be sure to maintain that same balance.

It's clear from the weight loss you cited and the improved blood pressure that has allowed you to stop taking medication that you're reaping a number of physical and emotional benefits from your current approach. We suspect that your family and friends are a bit in awe of what you do and what you have achieved. Just remain aware of what your body and mind are telling you and adjust accordingly.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Our uncle, who is 44, recently got diagnosed with a blood clot in his leg, and it was a medical emergency. Our mom (she's his older sister) is a nurse and says that because he's so tall -- 6-foot-4 -- his risk is higher. Is that really true? I thought that it depended more on weight than height.

Dear Reader: Kudos to your mother, who is up on the latest research. According to a study published last year in the American Heart Association's journal Circulation: Cardiovascular Genetics, scientists in Sweden have identified a potential relationship between someone's height and their risk of developing a blood clot.

In the study, men under 5 feet 3 inches were found to be 65 percent less likely than men taller than 6 feet 2 inches to develop a venous blood clot. In women, the likelihood of a blood clot was 69 percent lower in individuals shorter than 5 feet 1 inch than in those who were 6 feet or taller. For the taller men in the study, height was linked to blood clots in the lungs, legs and other locations. For women, being tall increased the risk of blood clots only in the legs.

These conclusions are drawn from an analysis of medical data collected from -- and this is an interesting twist -- more than 2.5 million adult siblings in a national registry. The study period ranged from 30 to 40 years, and siblings were used to help account for any potential genetic factors in the results. None of the subjects had venous blood clots at the start of the study period.

The ability of blood to clot, or coagulate, is crucial to our survival. When an injury occurs, factors present in our blood and plasma work together to form the clot, which slows or stops the flow of blood at the site. As the injury heals, the clot dissolves. However, blood clots can form within blood vessels absent of injury or trauma, and they can persist. The danger is that they can restrict blood flow.

Blood clots can also separate from their point of origin and travel through the heart and to lungs, where they become life-threatening. According to statistics from the Centers for Disease Control and Prevention, between 60,000 and 100,000 deaths per year are attributable to blood clots.

You're correct that being overweight or obese is a risk factor in developing a blood clot. So are smoking, pregnancy, being immobile for long stretches of time, having high blood pressure or high cholesterol, and family history, to name just a few. Although you can't stop being tall, you can take steps to reduce blood-clot risk.

The first three -- lose weight, exercise regularly and stop smoking -- not only lower blood clot risk, they contribute to health and well-being in general. Air travel, desk work, bed rest and medical recovery can mean sitting still for hours at a time. Mitigate this by walking, stretching and flexing your leg muscles at regular intervals. And if you do find yourself seated for a long while, avoid crossing your legs, which can impede blood flow.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)