Hello again, dear readers, and welcome back to the monthly letters column. It’s almost summer, which means it’s time to break out the hats, sunscreen and beach umbrellas, because a sunburn is a sign of skin damage. Unfortunately, that damage adds up with each additional sunburn, so please take the time to protect yourself. And now, onward to your letters.

-- A column about nasal irrigation, which uses sterile or distilled water to flush mucus and debris from the sinuses, is getting a lot of mail. We want to respond to one reader who wrote that she “snuffles tap water up my nose while in the shower, or over the sink, then gently blows it out.” We understand the point you made in your letter, that this is easier than using sterile water. However, as we said in our column, tap water is not safe to use in this way. It is not adequately filtered or treated, and it can contain microorganisms. The high pH of stomach acid makes it safe to swallow these microorganisms because it kills them. However, the environment of the nose and sinuses is a different story. The organisms can stay alive in the nasal passages and can cause potentially serious infections. In rare cases, they can even be fatal. For your safety, we hope you will consider switching to sterile or distilled water.

-- We recently wrote about a technique known as inspiratory muscle strength training, or IMST. It’s a type of resistance training that uses a handheld device to strengthen the muscles we use to breathe. In addition to helping people living with COPD and sleep apnea to breathe more easily, research suggests the technique can have a beneficial effect on blood pressure. This prompted a reader from Dallas to ask where he can buy the device. It’s often referred to as an RMT device. This is shorthand for inspiratory/expiratory respiratory muscle training. There are several different models, and all are widely available online. Some are also sold at large retail stores. These devices are drug-free and do not require a prescription. However, we recommend that you check in first with your health care provider about your plans to buy and use one.

-- We continue to hear from many of our readers who are interested in becoming part of a variety of clinical trials. We hope that a recap of the process will be helpful. Begin by visiting clinicaltrials.gov. This is a searchable database of clinical studies being conducted around the world. There’s a search box at the top of the page where you enter the name of your disease or condition. For studies that are seeking participants, you will also click the button labeled “recruiting and not yet recruiting.” Each study has its own webpage with detailed information about the study, its goals, criteria for participants and directions for how to apply.

Thank you, as always, for taking the time to write to us. We love hearing from you. We read all of your letters and will continue to respond to as many as we can.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: Whenever I hear about how we’re supposed to eat better and improve our diet, there’s always something about “healthy fats.” But no one ever explains what that means. What are these healthy fats that we’re supposed to be eating, and what makes them so great?

Dear Reader: It’s true that in discussions about a healthful diet, the focus tends to fall on eating lean proteins; getting a variety of fruits, vegetables, grains and legumes; and steering clear of ultra-processed foods. But healthy fats are an equally important part of the equation.

A robust body of research has revealed the wide-ranging benefits of including healthy fats in the diet. These include lowering the risk of developing heart disease, improving blood cholesterol levels, helping with blood sugar control and reducing inflammation. Healthful fats have a beneficial effect on blood pressure, and they have been shown to support gut health. There is also growing evidence that getting enough good fats in the diet helps to maintain the health of the lining of the gut. Known as the intestinal barrier, this plays a crucial role in numerous metabolic functions, including maintenance of the gut microbiome, absorption of nutrients and immune function.

Fats are a type of lipid, which are molecules that do not dissolve in water. When someone talks about healthy fats, they’re referring to lipids that, due to the specific types of chemical bonds that hold them together, remain liquid at room temperature. This is a category known as unsaturated fats.

These types of fats are further divided into two subcategories -- monounsaturated fats and polyunsaturated fats. Again, the distinction between the two arises from the chemical bonds in their structures. Polyunsaturated fats offer the same benefits as monounsaturated fats and also contain omega-3 and omega-6 fatty acids, which play an important role in brain function, skin and hair growth, bone health and metabolism.

Healthy fats are found in plant-based foods such as walnuts, flax seeds, chia seeds, soybeans, avocados and olives. They are present in vegetable oils, as well. These include olive, safflower, corn, sesame, canola, walnut and soybean oils. And don’t forget about fatty fish. These are an excellent source of a certain form of omega-3 fatty acid. Fatty fish, sometimes referred to as oily fish, include tuna, salmon, mackerel, whitefish, herring and sardines. Oysters, mussels and some types of fish roe are also good sources. A recent analysis of several large studies found that having two or more servings of fatty fish per week can help prevent cardiovascular disease in high-risk individuals.

Lovers of dark chocolate will be happy to know it contains monounsaturated fats, although in small amounts. Just remember that, while dark chocolate is rich in disease-fighting antioxidants, it also contains sugar and should be consumed in moderation.

Unfortunately, many of us don’t get adequate amounts of healthy fats in our diets. You can turn that around by cooking with vegetable oils, limiting saturated fats, avoiding trans fats and eating at least one good source of omega-3 fats each day.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: Would you please devote a column to shy bladder syndrome? This embarrassing condition is a significant inconvenience to many men. In severe cases, it’s a life-altering disability. I suspect there are more sufferers out there than one would imagine, but shame keeps them quiet.

Dear Reader: Shy bladder syndrome is a social anxiety disorder that makes it difficult -- or even impossible -- for an individual to urinate when someone else is present. The medical term is paruresis. Drawn from ancient Greek, the word has its roots in the words “para,” which indicates something atypical or abnormal, and “uresis,” which refers to the act of voiding the bladder. The term was coined in 1952 by two physicians, who were the first to describe the condition in a paper they published in the Journal of General Psychology.

Shy bladder syndrome is a common form of social anxiety, and it is believed to be second only to fear of public speaking in terms of humans’ apprehensions. The exact number of people it affects is not known, but studies suggest up to a quarter of the population has experienced it to some degree. It is seen more often in males, which has been attributed to the public nature of men’s urinals. However, the condition occurs in people of all genders, and of all ages, including children and adolescents.

When someone has shy bladder syndrome, they avoid using bathrooms other than those in their own homes. The possibility that someone else could enter the bathroom, or even overhear them using the toilet, can trigger the condition.

Voluntary urination involves neurons located in a small region in the brainstem known as Barrington’s nucleus. They send signals via the spinal cord to the urinary sphincter, which is the ring of muscle that controls the flow of urine from the bladder. When someone chooses to urinate, those nerve impulses instruct the sphincter to relax.

When someone has shy bladder syndrome, something disrupts that cascade of messages. The result is the person’s sphincter fails to relax, and they are unable to pee. It’s easy to dismiss this as a minor annoyance. But for those living with the disorder, it can range from embarrassing to disruptive, and in some cases, to outright dangerous. Being unable to use a public restroom can interfere with activities of daily life, including work, social interactions, relationships and travel. A routine urine test during a medical appointment or for employment purposes becomes an ordeal. People with severe paruresis will often restrict how much they drink in order to avoid the need to use a bathroom.

Consistently failing to empty the bladder when needed can cause health complications, including urinary tract infections. It can also cause damage to the muscles of the bladder, which, ironically, can lead to urinary incontinence. The good news is that the condition can be treated. This includes the use of relaxation techniques to reduce anxiety, psychotherapy, anti-anxiety medications and cognitive behavior therapy. A systematic program of desensitization known as graduated exposure therapy has been found to be particularly helpful. In order to rule out a medical cause of difficulty urinating, it’s important to see a doctor for a definitive diagnosis.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)