Dear Doctor: I just turned 55 and have noticed that I get winded faster these days when I go running. Does getting older affect how much air your lungs can hold? Is there any way to increase it?

Dear Reader: Yes, aging does have an effect on our lungs and how they function. In fact, the decrease in capacity begins about a decade after our lungs become fully mature, which is in our early- to mid-20s.

Your question addresses something known as tidal volume, which is the amount of air that moves into and out of our lungs with each breath. For healthy adult women, tidal volume is about 0.4 liters. For men, it’s about 0.5 liters. However, the volume of each breath is one of several variables that affect breathing function.

In addition to the lungs, the respiratory system includes the diaphragm, the dome-shaped muscle that separates the chest cavity from the abdomen; it also includes the ribs, sternum and supporting muscles and soft tissues, also referred to as the thoracic cage. Each of these plays an important role in breathing. The lungs hold the air, the motion of the diaphragm causes the lungs to fill and empty, and the thoracic cage provides support and protection.

As we age, the respiratory system undergoes gradual changes that affect its structure, physiology and immune function. Injury, poor posture, osteoporosis and the natural shrinkage of bones, muscles and soft tissues all contribute to a decrease in the size of the thoracic cage. This, in turn, has an effect on maximum air volume. A decrease in the strength of the diaphragm also affects how much air can be drawn into (and out of) the lungs. The lungs themselves lose elasticity with age, and the millions of tiny air sacs that they contain, known as alveoli, can lose shape and become “baggy.” Smoking and exposure to air pollution contribute to a decline in lung function. So do repeated respiratory illnesses, another reason to stay current with flu and other vaccinations.

The good news is that regular exercise can help to maintain lung function and tidal volume. Aerobic exercise is a great way to keep your lungs fit. Resistance training that targets the chest, shoulders and back muscles helps maintain strength and flexibility of the diaphragm and the thoracic cage. Breathing exercises, such as those done in yoga, are excellent tools for maintaining or increasing lung capacity. In deep breathing, also known as diaphragmatic breathing, you breathe in through the nose to fill your lungs from top to bottom. Be sure to also breathe out as deeply as possible, so you get the maximum volume of air moving through the lungs. Adding resistance to the exhale by pursing the lips or tightening the throat is also beneficial.

It’s important to remember that age-related changes to lung capacity occur gradually. If you ever experience a sudden or dramatic change to breathing, which can signal illness or injury, see your doctor right away.

(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: My husband has had very bad breath for several months, and lately he says he has a metallic taste in his mouth. Can you tell us what might be the cause?

Dear Reader: Bad breath is a fairly common occurrence, as is a metallic taste in the mouth. The cause of these is usually something benign, such as a lapse in oral hygiene. However, each can be a sign of a more serious condition, so it’s worthwhile to figure out what’s going on.

Let’s start with bad breath, or halitosis. A frequent cause is the presence of bacteria that live on the surface of the tongue, below the gumline and in the throat. These tiny organisms, which feed on the food particles left behind when we eat, emit an array of stinky gasses as a byproduct of their digestion. Two compounds in particular contribute to foul-smelling breath. They are hydrogen sulfide, which smells like rotten eggs, and methyl mercaptan, which smells like putrid cabbage.

Some foods that we eat, such as onions and garlic, can also contribute to bad breath. Additional common causes for unpleasant breath include the poor dental hygiene that we mentioned earlier; an infection in the mouth, teeth or gums; the use of tobacco products; or interactions with certain medications or multivitamins. Saliva plays an important role in keeping the oral cavity clean, and a condition known as dry mouth, or xerostomia, can lead to bad breath. Chronic acid reflux, sometimes referred to as gastroesophageal reflux disease, or GERD, is also associated with unpleasant odors in the mouth.

When it comes to the reasons for a metallic taste in the mouth, there’s a bit of crossover with halitosis. Poor brushing habits, certain foods and an oral infection can play a role. So can pregnancy, cancer treatments like chemotherapy and radiation therapy, and environmental exposure. Some medications may cause a metallic taste, as can multivitamins containing zinc or copper. People who follow low-carb diets often report developing a persistent metallic taste, a side effect of their bodies being in ketosis.

However, the complaint is also associated with several more serious conditions. The perception of unusual flavors can occur in certain cancers when tumor growth affects the complex cellular pathways involved in taste and smell. They can also occur in diabetes, as a result of alterations to glucose metabolism. Kidney disease, liver disease and some metabolic disorders, which are marked by a buildup of waste products, can cause both bad breath and changes to taste. Taste abnormalities are also often seen in people with dementia, due to disease-related changes in the brain.

Since both the bad breath and the metallic taste are somewhat recent changes, we think it would be a good idea for your husband to see his dentist. A thorough checkup will reveal any tooth decay, gum disease or infection. If nothing turns up and you’re still worried, consider a visit to your primary care physician, who can help identify any underlying medical problems that require attention.

(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: Our godson has cystic fibrosis, and seeing him struggle these past eight years has been hard. Is the new drug Trikafta we’ve been reading about really as good as people are saying?

Dear Reader: Yes, it appears that the new therapy you’re referring to is indeed a game-changer in the treatment of cystic fibrosis, or CF. Trikafta is a combination of three drugs, which target the cause of cystic fibrosis at the cellular level. In fact, the results of clinical trials were so promising, the Food and Drug Administration approved the treatment five months ahead of its deadline. The agency announced its decision on Oct. 21 and said that the new drug regimen is expected to help up to 90% of those living with the disease.

Cystic fibrosis is a rare and life-threatening disease in which a gene mutation causes the proteins found in mucus, sweat, tears, saliva and digestive juices to malfunction. Instead of remaining thin and slippery, the faulty gene causes these bodily secretions to become abnormally thick and sticky. The resulting mucus collects in the lungs and various digestive organs. This causes a dangerous buildup of mucus in the lungs, which makes it difficult to breathe and to get adequate oxygen.

People with CF are particularly vulnerable to lung infections, and they face eventual respiratory failure. Treatment thus far has focused on various methods of keeping the lungs clear. This includes the use of mucus-thinning and anti-inflammatory drugs, and physical interventions, such as vibrating vests to loosen mucus, which is then coughed up.

The disease also interferes with digestion, and it causes problems in the reproductive system. Your godson is one of about 30,000 people in the United States, and an estimated 75,000 people worldwide, living with the disease.

Although references to cystic fibrosis date back to the Middle Ages, it wasn’t until 1938 that cystic fibrosis was formally described as a disease. It took another 51 years for researchers to identify the specific gene mutation that causes it.

Three decades later, Trikafta represents the first major breakthrough in cystic fibrosis treatment. Patients in clinical trials saw dramatic improvements in lung function. At least one woman, who previously struggled to walk a short distance, celebrated by taking part in a 5K run. The drug, which is approved for patients 12 years and older, can cause potentially serious side effects, including liver problems and cataracts. Less serious side effects include headache, diarrhea, rash and stomach problems. Another potential challenge is the cost of the drug, which runs about $311,000 per year. And because cystic fibrosis can be caused by several mutations, some of them rare, the drug will not work for everyone.

Still, this new therapy is a cause for hope. Fifty years ago, it was rare for someone diagnosed with cystic fibrosis to live into their teens. Due to advances in chest physiotherapy to clear mucus from the lungs, cystic fibrosis patients typically now live into their 30s and 40s. With this latest breakthrough, the hope is that cystic fibrosis will move from a fatal disease to a chronic and manageable condition.

(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.)