Dear Doctor: I was informed several years ago that carbonated drinks weaken bones, leaching the calcium from them. Is this true? What would be considered an acceptable amount for a teenager or a woman past menopause? Would carbonated spring water be better?

Dear Reader: Sodas are ubiquitous in our society. Even schools sell them. Further, both parents and children often use sodas as their primary source of liquids, shunning simple water -- the essence of life. The evidence between soda intake and obesity risk is irrefutable. Now let's look at the evidence on bone density.

Almost 20 years ago, a study published in the Journal of Bone and Mineral Research found that cola-drinking rats had lower levels of calcium, higher levels of phosphorus, lower levels of vitamin D and higher levels of parathyroid hormone than water-drinking rats. They also had lower bone density in the femur (hip) bone.

A 2006 study published in the American Journal of Clinical Nutrition assessed the amount of cola and non-cola carbonated beverages, both with and without sugar, consumed by 1,125 men and 1,413 women. The study followed participants for 25 years and then checked their bone mineral densities. The authors did not find an association between non-cola carbonated beverages and lower bone mineral density in either men or women. Nor did they find an association between cola consumption and lower bone density in men. However, women who drank cola sodas had significantly lower bone mineral density than those who didn't drink sodas, regardless of whether the sodas contained sugar or artificial sweeteners.

Another American Journal of Clinical Nutrition study published in 2014 followed more than 73,000 women between the ages of 30 and 55 for 30 years. At the end of the study, they found that the rate of hip fracture was 10 percent greater among women who drank more than 10 sodas (of all types) per week, compared to those who did not drink any sodas.

The authors then compared women with the same body mass index who drank soda versus those who didn't. Here the authors found a significant correlation between soda intake and hip fractures. Women who drank five to 10 sodas per week had a 16 percent increased risk of hip fractures, and women who drank more than 10 sodas per week had a 42 percent increased risk of hip fractures. The increased rates of hip fracture were seen in both caffeinated and non-caffeinated sodas, as well as colas and non-colas.

Carbonated spring water is simply water with dissolved carbon dioxide gas, but that's not to say it isn't acidic. The pH level is between 3 and 4 -- higher than sodas' roughly 2.5 pH -- while water has a pH of 7. The acidity could potentially pose a problem, but a study published in the British Medical Journal in 2005 found no difference in markers for bone turnover between postmenopausal women who drank carbonated mineral water for eight weeks and postmenopausal women who drank plain mineral water.

My advice is: Make plain water your primary source of fluid. Also, and this is important: Minimize the amount of sodas that you and your teenager drink. In addition to their link to obesity, they do seem to increase the risk of low bone density and bone fractures.

(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: When I was growing up, I saw my doctor annually for a physical exam. So I was surprised when my daughter told me that her physician doesn't believe in them. Do you agree? If not, what should a physical exam include?

Dear Reader: Although there's a trend toward doing away with an annual checkup for healthy adults, both of us believe in and support the practice of a yearly physical exam. It's covered by most insurance policies and, at the very least, is an opportunity to reconnect with your primary care physician. When the annual exam becomes more than just an exercise in gathering data, it's an extremely useful tool for both the physician and the patient.

What exactly does a yearly exam consist of? That depends on each physician. Considering that the annual checkup has been one of the cornerstones of primary care, it's a bit of a surprise to note that there are no guidelines or consensus statements regarding what the visit should entail. We can't speak for other physicians here, but can instead explain what we do in our practices, and why.

In addition to performing a head-to-toe exam, we approach the annual exam as a chance to help our patients take stock. We review the previous year and plan for the future. We go over any active problems the patient may have, and evaluate how a treatment plan is (or isn't) working. We review any medications the patient is taking, with an eye to either renewing, changing or eliminating them. We update family medical histories to pinpoint any potential hereditary risk factors, such as certain cancers, coronary artery disease or Alzheimer's disease.

We believe that the results of these discussions, as well as the information gleaned from the screening and diagnostic tests, help patients obtain a clear picture of their physical health. They also offer patients an opportunity to set goals and play an active role in their health care. The lab tests and screenings that we recommend can not only reveal potential problems, but also provide an important baseline against which any future changes or anomalies can be evaluated.

Specifically, we review blood pressure, heart rate, weight and body mass index. For labs, we order a complete blood count, kidney, liver and thyroid function tests, diabetes and cholesterol screenings, and a check of vitamin D levels. For women, we recommend age-appropriate screening with mammogram, Pap smear and bone density test. With men, we discuss the risks and benefits of the PSA test, which screens for prostate cancer. For patients over 50, we recommend colon cancer screening with a colonoscopy. We review and advise vaccines.

The argument against an annual physical is that, for healthy adults, the tests are unnecessary. However, we believe that our approach yields a multidimensional picture of a person's health journey. It makes it more likely we will catch certain conditions early, when they are easier and less costly to cure. In our opinion, the annual physical exam empowers our patients and paves the way to better health.

(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: My hearing loss is related to my Eustachian tubes: They stay closed. I can open them and improve my hearing by holding my nose and blowing, but the effect lasts only a short time. Hearing aids don't help. What can I do?

Dear Reader: First, let's consider the size and location of the Eustachian tubes, one on each side of your head. Only half a centimeter wide, each one starts behind the nose and travels through cartilage and bone toward the middle ear, an air-filled chamber bordered on one side by the eardrum. The pressure within the middle ear should be equal to the air pressure outside, and the Eustachian tube is the only way for the body to equalize these pressures. This gas pressure homeostasis is necessary for optimal hearing.

The most common reason that the Eustachian tube closes is from inflammation within the tube and secretions that can block it from opening. With the tube closed, the middle ear has no way for the air to go in or out. When that happens, the air in the middle ear gets absorbed by the surrounding structures, creating a negative pressure in the middle ear. The sensation is similar to how your ears feel at the bottom of a pool. This negative pressure makes it even more difficult for the Eustachian tube to open, increasing to the point where fluid starts to fill the middle ear. In severe cases, blockage of the Eustachian tube can lead to vertigo and balance problems.

Now let's look at the possible causes for a closed Eustachian tube. In my experience, the most common cause is chronic nasal congestion, either from allergies or environmental irritants. Infection of the adenoids, sinus or nose also are likely causes; to determine this, an ear, nose and throat doctor would visualize the adenoids to assess their condition.

Chronic nasal swelling is another potential culprit. If that's the case, medications such as nasal steroids, leukotriene inhibitors and antihistamines could decrease the swelling, opening your Eustachian tubes and thus improving your hearing.

Note that one study, however, did not show significant change in Eustachian tube dysfunction with the use of a common steroid delivered via nasal spray, Nasacort. In addition, an over-the-counter expectorant, guaifenesin, could thin secretions sufficiently in the Eustachian tube to help clear it.

Essentially, the treatment depends on the cause. For inflammation and closure of the Eustachian tube caused by infection, antibiotics can help. For inflammation caused by acid reflux, which can lead to inflammation in the nasopharynx, look for ways to decrease acid reflux. If adenoids are blocking the Eustachian tube, the adenoids can be surgically removed.

As for medications, if those are ineffective, either balloon dilation of the Eustachian tube or laser therapy can be used to clear the opening in the nasopharynx.

Talk to your doctor about your symptoms. Eustachian tube dysfunction can be treated and, because symptoms can worsen, it should not be ignored.

Also, a note to my readers: A recent column on the potential link between proton pump inhibitors and heart disease referred to a study involving both clopidogrel and Plavix. In fact, they're the same drug. The reference should have said that researchers found an increase in the rate of heart events among those taking a proton pump inhibitor and clopidogrel/Plavix after angioplasty, but no difference in death rates. Thanks to those readers who pointed this out.

(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.)