Dear Doctor: Is there a cure for pancreatic cancer? Does anyone know what causes it? Does eating raw steak cause it? Or smoking?

Dear Reader: At this time, there is no known cure for pancreatic cancer, the third most deadly cancer in the United States. Symptoms of pancreatic cancer are so vague that they can be confused with a range of other diseases and conditions. Because there is no reliable screening test at this time to catch pancreatic cancer in its earlier stages, it is often diagnosed only after it has spread.

The pancreas is a spongy gland, about 6 to 10 inches long, wide at the head and narrow at the tail, with a shape that has been compared to a fish. Its job is to make enzymes to help with digestion and hormones that play a role in the regulation of blood sugar. The pancreas is located in the upper left part of the abdomen, between the stomach and the spine. Also surrounding it are the liver, spleen and small intestine, a location that adds to the challenge of making an accurate diagnosis when anything goes wrong.

The majority of the pancreas -- 95 percent -- is devoted to tissues that produce enzymes. The remaining 5 percent is made up of endocrine cells, which secrete hormones, including insulin. Cancer can start in either of these two types of tissues, but the most common form occurs in the enzyme-producing cells and ducts.

Although the exact cause of pancreatic cancer has not yet been identified, certain risk factors are known. As you mention, cigarette smoking is one of the risk factors. So is a family history of the disease, as well as repeated bouts of pancreatitis, an inflammatory condition in which the pancreatic enzymes build up and begin to digest the organ. Pancreatic cysts are also believed to be possible precursors of cancer. We don't know of a connection between eating raw beef and this type of cancer.

When cancer develops in the pancreas, it interferes with the normal functioning of the organ. This results in symptoms that can include pain in the upper abdomen, fluid build-up, nausea, weight loss, jaundice, poor appetite, loose and foul-smelling stools, or diarrhea. In some cases, the sudden onset of diabetes can be a symptom of pancreatic cancer. But as we mentioned before, the location of the pancreas, deep in the abdomen and amid a cluster of other organs, makes it a challenge to accurately identify the source of the symptoms.

Treatment includes surgery, chemotherapy, ablation (extreme cold or heat), radiation and certain drug regimens. The approach chosen depends on the type of cells that are involved, the age of the patient and the stage of the disease. Also a factor is how the patient feels about the possible side effects of a recommended treatment, and the likelihood that it will be helpful.

Despite being a deadly cancer in which survival rates have not measurably improved in 40 years, pancreatic cancer has a low profile. In our opinion, research money directed to developing a reliable screening test for pancreatic cancer should become a priority.

(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.

(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.)

(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: 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.