Dear Doctors: My blood pressure is on the edge of the normal range. My doctor wants me to think about something called the DASH diet. What is that? I want to stay healthy, but I know myself: If I can’t have a diet that is enjoyable, I’m not going to be able to stick with it for long.

Dear Reader: Here in the United States, high blood pressure is common and a serious health concern. Data shared with the Centers for Disease Control and Prevention show that close to half of all adults -- and even some children -- are living with chronic elevated blood pressure. When this goes untreated, it can cause damage to the heart muscle, circulatory system and kidneys.

Persistent high blood pressure puts the person at increased risk of having a heart attack or stroke. It can damage blood vessels in the eyes and lead to vision loss, play a role in sexual dysfunction and contribute to cognitive decline.

The DASH diet that your doctor has recommended dates to 1997, when the results of a clinical trial into its principles were published in the New England Journal of Medicine. The name is an acronym of Dietary Approaches to Stop Hypertension. The study’s authors wanted to measure how varying amounts of fresh fruits and vegetables in someone’s daily diet would affect their blood pressure.

They found that the group of study participants who ate four or five daily servings of fruit, plus four or five servings of vegetables, saw the most significant improvements to blood pressure. The DASH diet also includes several servings per day of whole grains, lean proteins and healthful fats. More than two dozen follow-up studies into this approach to eating have confirmed the original findings.

The DASH diet study was not designed to pinpoint why it improves blood pressure. However, potassium, an electrolyte that helps keep the walls of blood vessels relaxed and pliable, is widely believed to be a driver behind the impressive results.

Potassium and sodium work together to maintain fluid balance in the body. This, in turn, influences blood pressure. The optimal ratio of the two electrolytes is about three parts potassium to one part sodium.

However, the typical American diet, so heavy in sodium, often delivers the reverse. While dietary sodium has long been the focus of blood pressure management, recent research suggests the sodium-potassium ratio is more important.

With its abundance of fruits and vegetables -- many of which are rich in potassium -- the DASH diet provides an abundant supply of this crucial nutrient. People who follow the diet also get the recommended amount of fiber per day, which helps nourish the trillions of microbes in the gut. The eating plan also includes a daily sweet treat.

In recommending the DASH diet, your doctor is offering you a drug-free path that can help you gain control of your blood pressure numbers. We hope you, and perhaps some of our readers with blood pressure issues, will consider giving it a try.

(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.)

Kansas City, MO 64106; 816-581-7500

Hello, dear readers, and welcome to our monthly letters column. With lengthening days and warming weather, outdoor activities beckon.

Please remember to protect yourselves from the sun, whether with sunscreen, UPF clothing or, ideally, both. Tick protection is also important when you’re venturing into the great outdoors, as the data show tick-borne illnesses are still on the rise. We’ll have a column on the topic soon. Now, on to your letters.

-- Speaking of being outdoors, we have written several columns about the mental health benefits of spending time in the natural world. We recently received a question on the topic from a reader in the Chicago area: “Do you get the same good results from being in nature if you’re on the phone the whole time?” he asked. “My brother says he wants to de-stress -- but whenever he’s hiking, he’s always wearing a headset and making or getting phone calls.”

Research has found that the sights, sounds, scents and physical sensations of being outdoors can lower cortisol and increase serotonin, each of which can help us feel better. If you’re on the phone, your awareness of these is at best diminished or, at worst, eclipsed.

Your brother’s headset habit doesn’t interfere with the physical gains of the hiking he does. However, it can create a barrier between him and the natural world, and thus diminish, if not erase, the mental health benefits.

-- A recent column discussed dandruff, a common skin condition that causes scalp flakes to develop and shed. This prompted a question from a concerned reader: “I’ve been seeing someone who has really bad dandruff and doesn’t seem to be doing anything about it,” they wrote. “The thing I’m worried about is if it’s contagious. Am I going to get dandruff if we sleep on the same pillow?”

Dandruff can be caused by dry or inflamed skin, contact dermatitis or chronic skin conditions such as psoriasis or eczema. Most often it is caused by an overgrowth of a yeastlike fungus. This fungus is naturally present in the scalp, but in some individuals, it leads to an overgrowth of skin cells and results in the flakes we know as dandruff. You will be happy to know that the condition is not contagious.

-- We continue to get letters asking for another update to the clinical trial exploring the use of stem cells in the management of Type 1 diabetes. The initial phase of the trial was quite small, with just 17 participants. However, the early results, in which several participants ceased needing injected insulin, hinted at a possible breakthrough.

A new phase of the study has been completed, and we will be back soon with a column on it. We’ll discuss the results, explore the promises and explain the potential dangers of the treatment.

Thank you to everyone who has taken the time to write. We love hearing from you. If it occurs to you, please include your city or state or region in your letter. We really enjoy knowing where you are writing from.

(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.)

Kansas City, MO 64106; 816-581-7500

Dear Doctors: I recently started going to a yoga class at our community center. We were doing deep breathing, and it felt like my lungs weren’t filling up as much as they used to. Do your lungs get less elastic when you get older? Can that be reversed?

Dear Reader: The lungs, which are a pair of balloonlike organs located in the chest cavity, are really quite remarkable. With each inhale, they make possible the rapid transfer of life-sustaining oxygen to the bloodstream. Each exhale offloads carbon dioxide, which is a waste product.

The lungs are firm enough to maintain their shape, yet elastic enough to expand and contract with each of the estimated 22,000 (!) breaths we take each day. They are also a marvel of bioengineering. A network of branching airways gradually decrease in size, terminating in clusters of minute sacs known as alveoli. In a healthy adult, these number between 300 million to 500 million and provide between 540 and 810 square feet of surface area for the gas exchange we discussed earlier.

The elasticity of our lungs arises from two distinctive features. One is a protein known as elastin. When tissues in the body require elastic recoil to fulfill their function, elastin is usually present. Collagen, a structural and pliant protein, also plays an important role.

Another factor in lung elasticity is surface tension. This is specific to the tiny sacs of the alveoli. Small and fragile, they rely on a substance known as a surfactant to provide the surface tension needed to keep them from collapsing when we exhale. The combined actions of elastin, collagen and surface tension, along with a supporting network of muscles and connective tissues, create lung capacity. This is the total volume of air in the lungs when you breathe in as much as possible.

When it comes to a decrease in lung capacity, a number of factors come into play. A universal one is age. While lung development concludes at about age 8, our lungs increase in size and capacity as we continue to grow. Lungs reach maturity by about age 20 or 25. About a decade later, lung capacity begins a gradual age-related decline. Exercise, general health and smoking each play a role in how much and how quickly this occurs.

Additional causes of decreased lung capacity include respiratory illnesses, such as chronic bronchitis, emphysema, asthma and COPD. Severe pneumonia, which causes inflammation, can scar the delicate tissues of the alveoli and also lead to diminished lung capacity.

Unfortunately, changes to the tissues that contribute to lung elasticity cannot be reversed. However, you can take steps to help maintain -- and perhaps improve -- lung capacity. The yogic deep breathing you have begun doing is excellent for that. So is exercise in general. The trick is to make both a part of your daily routine. A healthful diet and maintaining a healthy weight are also important.

And we hope this goes without saying, but smoking is the enemy of lung health, and health in general. Please, if you are a smoker, consider crafting a strategy to quit.

(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.)