Dear Doctor: I'm 58 years old and have begun leaking urine. Once it was while I was at exercise class and another time when I sneezed. I've never had children, so why is this happening? What can I do?

Dear Reader: First, we'd like to reassure you that you're not alone. Urinary incontinence is quite common among women of all ages. Up to 45 percent of women will experience some degree of urinary incontinence, or UI, during their lifetimes. That's twice the rate of UI as occurs in men.

Urinary incontinence is when, due to a lack of bladder control, urine is accidentally released. Although UI falls into two main categories -- stress incontinence or urge incontinence -- some women will experience a combination of both, known as mixed incontinence.

Stress incontinence is when physical movement places pressure on the bladder and causes urine to leak. Urge incontinence is the strong and sudden need to urinate, followed immediately by involuntary bladder contractions that cause it to empty. With either type of incontinence, how full the bladder is doesn't matter.

People with Alzheimer's disease, individuals with damage to the spinal cord or brain, and people with certain neurological conditions like multiple sclerosis or Parkinson's disease can also often experience UI. Temporary UI may be caused by certain medications, drinking large amounts of fluids, a urinary tract infection and constipation, which can exert pressure on the bladder.

From your description, what you have experienced is stress incontinence. It occurs because the muscles of the pelvic floor, which supports the bladder, and of the urinary sphincter, which controls the release of urine, have weakened. As a result, any physical movement that puts pressure on the bladder -- a cough, laughing, lifting a bag of groceries -- may overcome the impaired resistance of the urinary sphincter and cause urine to be released.

You're correct that the physical changes that take place during pregnancy and childbirth can contribute to UI. However, other factors, like weight gain, obesity, menopause and the physiological changes associated with advancing age, can also play a part.

It's a good idea to check in with your family doctor. He or she may ask for a urine sample to rule out infection, and to check for traces of blood or other problems. Bladder function tests and a review of your medical and family history can help your doctor to pinpoint any external factors playing a role in the onset of the UI.

How much the UI bothers you will factor into what steps you take next. Many patients are comfortable using a panty liner to absorb a minor amount of leakage. In severe cases, surgical interventions are possible. At this time, there are no approved medications in the United States to address UI.

In the majority of cases, doctors recommend certain changes to lifestyle and behavior. It's possible you'll be asked to manage how much you drink and at what times. Losing excess weight is often helpful. And exercises known as Kegels, which work the muscles of the pelvic floor, can return strength and tone to help you to regain control.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Are there foods and drinks that can help firm up loose stool, so that there isn't an occasional "surprise" when passing gas? Probiotics haven't helped, and multiple tests have proven negative for anything but chronic inflammation.

Dear Reader: We're glad to hear that your doctor has ruled out a medical cause for your experience with loose stools. And since you haven't referenced diarrhea, we'll assume that's not relevant to the issue you're having.

In many cases, this is the result of something in the diet, so let's start with the basics of digestion.

For the most part, digestion is a "wet" process. Food goes into our mouths and we chew, adding saliva to substances that, to some degree or other, already contain moisture. In the stomach, the chewed food gets further broken down by powerful acids, which deliver a liquid slurry to the small intestine.

Here, digestive juices from the pancreas, liver and intestine finish the dismantling process. The digested nutrients are then absorbed by the walls of the small intestine, where they enter the blood and are delivered to the rest of the body.

As the waste products that are left behind begin to move through the large intestine, the stool is formed. The job of the large intestine is to absorb water from these waste products, along with any stray nutrients. This process changes the waste from a liquid form into the firm mass of the stool. This is then stored in the rectum until a bowel movement occurs.

The upshot is that loose stool is the result of excess water that was not removed by the large intestine. Since illness and infection aren't the cause, let's look at diet.

Dietary sugars, which can increase the absorption of water, may exacerbate loose stools. That's in part because sugar is hygroscopic, which means it attracts and absorbs water. In addition, some people lack adequate enzymes to digest certain sugars. These sugars can include sorbitol, which is found in prunes, peaches and apples; mannitol, which is found in pineapples and asparagus; and xylitol, a sugar present in lettuce and strawberries. Each of these can have a laxative effect. The sugars in wine and beer can cause loose stools, as can lactose, the sugar found in milk products.

Caffeinated beverages, fried foods, fatty meats and additives like MSG and artificial sweeteners can also cause problems. In fact, for many individuals who experience digestive problems, the question may be not what to add to your diet, but what to eliminate from it.

If you're up for it, you might try an addition diet. Start with a small but nutritious range of foods that result in normal bowel movements. Think lean meats, small portions of vegetables, and potassium-rich foods like bananas. Then, one by one, begin to expand the range of foods in your diet. There are probably certain foods that your body absorbs better than others.

By proceeding slowly and keeping a food diary, you may be able to pinpoint the culprits and tailor your diet to your specific needs.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Our older sons both played football in high school, but that was before all the publicity about concussions. Our youngest son is now old enough to try out for the team. Is it really that dangerous?

Dear Reader: Sports offer kids a lot of benefits. There's the physical exercise, the social aspect of being part of a group with a common goal, the lessons about teamwork, leadership and work ethic, and how to win -- and lose -- with grace. The tradeoff, of course, is the risk of injury.

In a competitive atmosphere, you're going full tilt, throwing yourself into the moment with everything you have. Even in a game as seemingly genteel as badminton, you can sprain an ankle, strain a muscle, break a bone or, if you run into another player or object, even sustain a concussion.

That said, football is in a category of its own. Collisions aren't accidental; they're an integral part of the game. Specialized equipment like helmets and braces and pads do offer a measure of protection. But, as you realize, there are variables at play that can have grave and lasting consequences.

We checked with the Centers for Disease Control and Prevention, and it turns out that 2.6 million children and young people under the age of 20 seek treatment in the ER each year for sports injuries. In football, knees and ankles are the most frequent sites of the injuries. A common sports-related injury we see in our practices is a tear to the ACL, the anterior cruciate ligament. That's one of two ligaments that help to stabilize the knee joint. This happens when the lower leg is firmly planted and momentum of some kind sends the body moving in an opposing direction.

Additional injuries sustained by football players include bruises, sprains and strains, broken bones, bruised or damaged internal organs, back injuries, spinal cord injuries and, of course, concussion.

Concussion may not be the most common football injury, but it can be among the most serious. That's because instead of just a bump on the head, a concussion is actually a mild form of traumatic brain injury. In a concussion, the blow to the head is severe enough to cause the brain to literally move back and forth within the skull. This results in physical and chemical changes to the brain tissue that can leave lasting damage.

Some school football programs have successfully limited the amount of head impact among their players by instituting specific safety rules for both practice and play. Advances in protective helmets have also proved helpful. However, as we all know, in an actual game situation, young athletes don't hold back. Football is a contact sport. No matter the precautions taken, the risk of injury -- including concussion -- still exists.

We recommend that you check with the school and the coach and learn what protections are in place. Bring your family doctor into the discussion. The truth is, football offers both risk and reward. With adequate information, you'll know which decision is right for your family.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)