Dear Doctor: A dear friend is about to start chemotherapy treatments, so I've been researching the side effects she can expect, and it’s a lot. I’ve read that even her sense of taste could change. Is that true? Can anything be done?

Dear Reader: You’re correct about the wide range of potential side effects that can occur during treatment for cancer. Although we tend to be most familiar with the nausea, hair loss and fatigue that often accompany chemotherapy, adverse side effects can arise from many different cancer treatments.

In addition to chemotherapy, treatments include radiation, hormone, precision and immunotherapies. In the course of targeting and disrupting cancer cells, these therapies can result in swelling, bruising, anemia, infection, nerve pain, memory problems, urinary and bladder issues, diarrhea, loss of appetite and as you have discovered, changes to the sense of taste. The sense of smell, which is closely linked to our ability to taste, can be affected as well.

A loss of appetite and changes to taste may seem like the least challenging side effects in that daunting list, but they can have a profound effect on a patient’s ability to both withstand the rigors of treatment, and to their successful recovery once treatment has concluded.

Due to physical side effects like nausea, pain and fatigue, patients often lose their appetites. This makes proper nutrition and maintaining weight a common struggle for cancer patients. Add in an altered sense of smell and taste, and the goal of a nourishing diet becomes even more of a struggle. That’s why we think it’s wise for patients to work with a registered dietitian to help with specific nutritional needs during treatment, and during recovery as well.

Changes to taste often accompany certain cancer medications, which can alter the communication between the brain, which interprets taste and smell, and the receptors in the mouth and nose. Dry mouth, mouth infections and sores in the mouth and gums can also affect taste. Patients often report that foods take on a metallic taste, or come across as acidic, bitter or even rancid.

Though these changes can’t be reversed during treatment, there are strategies to help patients manage them. Patients who find that certain foods taste bad, even those that were previous favorites, shouldn’t force themselves to eat. Instead, experiment with small amounts of other foods to find something more tolerable, even if they’re odd or unfamiliar. Foods served at room temperature or chilled will often carry less scent and flavor than those that are hot. Fresh and frozen fruit and vegetables won’t carry the same tinny taste of canned foods.

The American Cancer Society suggests rinsing the mouth with a solution of 1/2 teaspoon of salt and 1/2 teaspoon of baking soda, mixed into a cup of warm water, to help stop bad tastes. It’s also important to practice good oral hygiene, brushing several times each day and flossing. We’re happy we can end with the good news that, for most patients, taste and smell return to normal in a few months following the end of treatment.

(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: One of the yoga teachers at our gym always goes on and on about the importance of the vagus nerve whenever we do deep-breathing exercises to relax. What is she talking about, and why is it important?

Dear Reader: Your yoga instructor is referring to one of the attributes of the ever-fascinating vagus nerve, which is the most complex of the 12 cranial nerves. Like each of the cranial nerves, the vagus nerve arises directly from the brain rather than the spinal cord. It’s the longest of these nerves, and it travels a meandering path through the body, beginning in the brain, through the face, neck and upper body, and to the abdomen, where it ends in the colon. In fact, its name derives from the Latin word for "wandering."

Along the way, the vagus nerve divides, branches out and exchanges fibers with numerous other nerves, thus playing a role in an impressive array of our sensory and motor functions. It’s one of the crucial links between the brain and the neck, lungs, heart and abdomen, and it helps to regulate mood, heart rate, digestion, anti-inflammatory and immune response. The gut and brain communicate via the vagus nerve, as do many other parts of the body.

There’s so much to tell about this remarkable structure that we could easily fill several columns and not scratch the surface. So let’s get right to your question about the vagus nerve and deep breathing.

One of the functions of the vagus nerve is to communicate with the diaphragm. That means that when you’re taking the slow, deep and controlled breaths associated with yoga, which engage the muscles of the abdomen and the diaphragm, you’re stimulating the vagus nerve. And since vagal stimulation has been found to help lift mood, lessen anxiety and even lower blood pressure, it follows that you can trigger this relax-and-restore response by doing some deep breathing exercises.

What’s great about diaphragmatic deep breathing is that it’s portable. You can do it anywhere, at any time, without any special equipment. And the bonus is that you can practice it in public without anyone knowing you’re doing it. If you have a home-based blood pressure device, you can do your own experiment about the benefits. Start by taking a baseline blood pressure reading without any special preparation. Follow this with a few minutes of diaphragmatic breathing. For anyone who has never tried it, it’s slow, deep breaths that fill the lungs from bottom to top. Be sure to relax and soften the muscles of the belly, which will pop out a bit as you breathe, to get the full beneficial effect.

Holding the breath for five to 10 seconds also stimulates the vagus nerve. So does adding a bit of resistance to the exhale, which can be achieved by blowing out through pursed lips. Not only do these breathing techniques have the potential to impart a sense of calm and relaxation, they quiet the fight-or-flight response in our bodies. And as you’ll see if you try the blood pressure monitor experiment, they will often yield a lower blood pressure reading.

(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: Are those wireless earbuds everyone seems to be wearing nowadays safe? I heard that some international researchers are petitioning the World Health Organization about them because the signals that they emit may be hurting our brains. Should we be concerned?

Dear Reader: When it comes to wireless devices, which have been swiftly and near-universally adopted over the last two decades, advances have far outpaced our ability to monitor or even understand the potential health effects and consequences.

Wi-Fi, which first became commercially available in 1997, is one of the fastest-growing technologies in history. Cellphones quickly moved from a pricey niche product to the ubiquitous pocket computers of today, their telephone functions now barely an afterthought. (Fun fact -- the first truly wireless phone call was made in 1973 on a "mobile" phone that weighed 2.5 pounds.) And now, with the advent of wireless earbuds, phone manufacturers are bringing wireless tech into even closer and more sustained contact with the body.

At issue are EMFs, or electric and magnetic fields. These fall into two categories -- ionizing and non-ionizing. Ionizing EMFs are high-level radiation with the potential to cause damage to cells and DNA. Non-ionizing EMFs, which are low-level radiation, are the ones generated by wireless devices. Non-ionizing EMFs haven’t been proven to be harmful to humans. But they haven’t been shown to be harmless, either, and so the debate rages on.

As you point out in your letter, some scientists and researchers are raising an alarm. In 2015, a group of 250 doctors and scientists who specialize in EMF research signed a petition directed at the WHO and the United Nations. In it, they state their belief that the non-ionizing EMFs released by wireless devices pose a range of health hazards. These include cancer, memory problems and reproductive and genetic disorders. The U.S. Food and Drug Administration, meanwhile, does not consider the low-level EMFs released by cellphones and wireless devices to be a health hazard.

The debate about non-ionizing EMFs doesn’t hinge on the power of the energy fields generated by our wireless devices, which everyone agrees are on the low end of the non-ionizing EMF spectrum. Instead, it focuses on the effects of sustained exposure from the growing number of wireless devices we’re letting into our lives. Now, with wireless earbuds being placed into the ear canal, the concern is that we have moved from being bathed in non-ionizing EMFs from a distance to directing them into our bodies and close to our brains.

As we mentioned earlier, the results of ongoing research into the health effects of low-level EMFs remain mixed at this time. Scientists point out that Bluetooth devices, which include wireless earbuds, give off less than 10% of the radiation of cellphones. But if you’re at all worried, skip the wireless earbuds and stick with the old-school wired ones. Yes, it’s true that a number of cellphone manufacturers have ditched the headphone jack in their devices in recent years, but you can get an adapter that lets you used wired earbuds or headphones.

(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.)