Dear Doctor: Just how bad is it to give kids fruit juice before they turn 1?

Dear Reader: Fruit juice has been touted as "part of a nutritious breakfast" for years. As a child, I was told that juice was good for me, providing me with vitamin C. After all, it was a healthier alternative to sodas, and it tasted good. Today, kids routinely drink cranberry juice, orange juice, grape juice, apple juice and many other juices for those reasons. But now, with the epidemic of obesity and diabetes, adults are starting to think more carefully about the sugar content of fruit juice.

Fruit juice contains four sugars: sucrose, glucose, fructose and sorbitol. All of these, except sorbitol, are easily absorbed by the body and raise blood sugar and insulin levels. In addition, the sugars from juice that are not absorbed can cause bloating, abdominal pain and diarrhea in toddlers.

Another problem with fruit juice is that you easily get all the sugar of a fruit, but without the fiber. Take orange juice, for example. If you were to eat an orange, your hunger might be satiated enough not to eat another, thus limiting your sugar and caloric intake. However, an 8-ounce glass of orange juice might require four oranges. This is true for many other fruits as well. That's a lot of sugar and calories, with all their negative effects.

A recent policy statement from the American Academy of Pediatrics suggests that infants who drink fruit juice may be less likely to eat fruits when they are older, and, further, infants might be replacing milk with juice. Milk, in addition to sugar, has a substantial amount of the protein, fat and vitamins necessary for growth. However, juice has sugar and some vitamins, but no protein or fat. Not convinced? Excessive consumption of juice in children has been associated with malnutrition and short stature. (Note that because water lacks nutrients, it's not recommended for infants younger than 6 months.)

Another worry about the sugar in fruit juice is the effect it has on young teeth, because prolonged exposure to sugar leads to cavities. The risk is heightened when infants are given juice in a bottle or sippy cup, because they can carry the bottle or sippy cup with them -- drinking whenever they want. Both the American Academy of Pediatrics and the American Academy of Pediatric Dentistry recommend that juice be given only in an open cup to minimize how much a child drinks.

I agree that giving juice to children younger than 1 year of age is not healthy for them. But the same holds true for those older than 1. Juice may have some health benefits, but overconsumption will still ultimately lead to a greater risk for obesity, cavities and diabetes. So parents of older children should continue to control their consumption of juice. And, because they're not reliant on liquids for nutrition, teaching them to use water to slake their thirst is a good idea.

We've focused here on drinks that are 100 percent juice. The unhealthy elements of juice become even more pronounced when sugar is added to create a "fruit drink" or a "juice cocktail."

I understand that it's hard for a parent to say no to a crying infant who craves juice or a fruit drink. But doing so is much easier than trying to change entrenched unhealthy habits.

(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: I just heard that instead of causing injuries, running may be good for your back. Is this true? If it is, I'm going to lace up my shoes and head back out to the trail!

Dear Reader: Running is one of those physical activities that, over the years, has accrued an almost mind-bending cache of contradictory advice. So it's no wonder that the results of a new study, which suggests that running can improve the health of the discs in your spine, have caught you by surprise.

Let's start with a look at the spinal column, which as we've said before is a marvel of engineering. With a minimum of moving parts, this gently s-shaped curve of bone, cartilage, collagen and protein gels supports the body and gives it structure. It allows multi-directional movement and protects the vital bundles of nerves that connect the brain to the rest of the body.

The vertebrae are the series of load-bearing bones that articulate the spine. These are connected to one another by gel-filled discs, which also act as shock absorbers. But the same interlocking structure that lends flexibility to the spine is also its most vulnerable feature.

How the repetitive stress of running affects the various parts of the spine, particularly the discs, has long been a subject of debate. In the study published last spring, scientists from Australia set out to answer the question and learn whether intervertebral discs can be strengthened. To that end, they studied the spines of 79 men and women between the ages of 25 and 35. One-third of them were not runners. In fact, that group rarely exercised at all. Of the runners in the study, all had been training for at least five years, and regularly logged anywhere from 12 to 30 miles per week.

With the use of advanced imaging techniques, the researchers measured the size and resilience of each participant's spinal discs. The results were surprising. The runners in the study, whose regular exercise regimen placed repeated demands on the shock-absorbing qualities of the spine, had intervertebral discs that were larger and filled with more fluid than did the group who rarely exercised. That is, their discs were healthier than those of the non-running participants.

Even more intriguing was the fact that the size of the vertebrae of the joggers, who totaled 12 to 25 miles per week, and the long-distance runners, who ran as much as 70 miles per week, were virtually the same. That is, total mileage didn't matter. Longer runs didn't make the spine healthier, nor did they cause deterioration.

Those of us who aren't runners will be happy the scientists didn't stop there. By parsing their data even further, they discovered that the health effect on intervertebral discs begins at a pace of 4 mph, or a brisk walk.

Although a single study can't definitively answer whether running is good or bad for the back, the results here add a layer of fascinating and encouraging information for runners and walkers alike.

(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: 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.)