Dear Doctor: Our family loves the summer barbecue season, but the “take the fun out of everything” lobby keeps saying this can increase our risk of cancer. Just how unhealthy is grilled meat? Can we do anything to make it safer?

Dear Reader: The potential health threat of grilled meat is one of those cyclic news stories that pops up each spring as reliably as the first crocuses. The issue has its roots in decades of science, but the subsequent writing about the potential risks has ranged from measured and helpful to off-the-charts alarmist. To sort through the noise, let’s start with some basics.

When we cook meat over high heat, or to high temperatures, a number of chemical compounds, a few of them potentially dangerous, are formed. The grilling of beef, poultry, pork, fish and other muscle meats creates heterocyclic amines, or HCAs. These are formed not only in grilling, but during other high-heat cooking, such as broiling, pan frying and deep frying. When meat juices ignite on the hot coals beneath the grill, or when they come into contact with any surface hot enough to evaporate liquid and create smoke, that smoke contains chemical compounds called polycyclic aromatic hydrocarbons, or PAHs. When the smoke comes into contact with the meat -- and whatever else is on the grill -- it leaves behind potentially dangerous compounds. Lab experiments have shown that HCAs and PAHs have the potential to cause changes to DNA, which means that they may increase the risk of cancer.

So far this all sounds pretty grim, so it’s helpful to put things into context. In lab experiments, most of them conducted in test tubes and in animals, researchers use doses of HCAs and PAHs that are extremely high, the equivalent of thousands of times the exposure of a person eating a typical diet. By comparison, the levels of HCAs and PAHs generated by home cooking and grilling methods are quite low. However, ongoing population studies continue to find a link between grilling and a slight increase in cancer risk. The takeaway here, as with so many pleasures in life, is moderation.

When it comes to grilling, a few simple steps can make your meal safer. First, grill meat separately from other foods to limit exposure to PAHs, the compounds contained in rising meat smoke. Vegetables, fruit, bread and pizzas, all popular grilling options, should be cooked at a different time from the meat, or at the very least on their own side of the grill. When it comes to meat, it’s wise to avoid high cooking temperatures and prolonged cooking times. Turning meat frequently while it’s on the grill helps keep charred areas from forming. Be sure to remove any charred portions before serving and eating.

A final note -- studies have shown that acidic marinades that contain no sugar (but spices are fine) can significantly reduce the formation of PAHs. A marinade of lemon juice reduced the generation of PAHs by 70%, while lemon juice mixed with oil reduced PAHs by 57%. We hope this helps, and that you have an enjoyable and healthful grilling season.

(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: A relative of mine was recently diagnosed with Parkinson’s disease. I read recently that exercise can help slow the progression, so I want to suggest it to him, but I don’t know if it’s actually true.

Dear Reader: Although Parkinson’s disease is a progressive neurologic disorder that increasingly limits a person’s ability to move, a robust body of research points to the benefits of exercise for people with the condition. Symptoms of Parkinson’s, which typically appear gradually, can include tremors, poor balance, slowed body movement and stiffness. Most cases are diagnosed in people 60 and over. At this time, an estimated 1 million Americans have been diagnosed with Parkinson’s. With thousands of baby boomers turning 65 each day, the number of Parkinson’s diagnoses is expected to spike.

Older studies have shown that a variety of exercises help with a range of issues common to Parkinson’s, including balance, flexibility, strength and motor coordination. For example, the slow, sustained movements of tai chi and yoga help improve gait and balance, while aerobic exercise enhances endurance, agility and coordination. But when it comes to actually slowing the progress of the disease, we think you’re referring to a study conducted by researchers at Northwestern University’s Feinberg School of Medicine. The results were published in JAMA Neurology in December 2017.

This study, which researchers say is the first of its kind, explored the potential benefit of high-intensity exercise for patients with early-stage Parkinson’s disease. Previously, high-intensity exercise was not considered appropriate for Parkinson’s patients. Each of the 128 patients enrolled in the study had early-stage disease and had not yet begun taking any medications. This was done to eliminate response to medication as a variable in the study.

The participants were divided into three groups and had their baseline physical condition evaluated according to a Parkinson’s disease scale. During the six-month study, one group of patients exercised three times per week at high intensity, which was defined as 80% to 85% of maximum heart rate. A second group exercised three times per week at medium intensity, or 60% to 65% of maximum heart rate. The third group, which served as the control, did not exercise.

After six months, participants were re-evaluated on the Parkinson's disease scale, which ranges from 0 to 108. The lower the number, the less severe the symptoms. For those who did high-intensity exercise, the group’s baseline reading of 20 remained unchanged. For the patients who exercised at moderate intensity, their baseline reading of 20 increased by 1.5 points. For the control group, which did no exercise, their baseline reading of 20 increased to 23. As the researchers point out, that 3-point increase translates to a 15% increase in primary signs of the disease. Not only is this statistically significant, it results in a lower quality of life for patients.

If you share this study with your relative, please urge them to check with their doctor before starting any kind of exercise program. Decisions best made with a physician’s help include which specific exercises to take part in, which to avoid, and intensity and duration.

(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: A good friend of mine is into this new thing called resistive breath training. She says it helps runners build endurance, and she even bought a breathing gadget to practice it. Does it really help?

Dear Reader: Resistive breath training, also known as inspiratory muscle strength training (IMST), is a type of resistance training for the muscles we use to breathe. It can be accomplished through a series of controlled breathing exercises or, as your friend is planning, with a hand-held device. Known as an inspiratory muscle trainer, this type of device typically consists of a mouthpiece through which the person breathes and some sort of adjustable valve that creates varying degrees of resistance for the exerciser to work against.

While IMST may not be familiar to you and your friend, it’s not actually a new technique. Resistive breath training was developed many decades ago to help people with various breathing problems, including COPD, asthma and the after-effects of bronchitis. It is also used to help people to successfully withdraw from mechanically assisted breathing.

In a study dating back to 1979, researchers found that IMST helped patients living with severe COPD to achieve improved breath control, as well as improved expectoration, the ejection of phlegm and mucus from throats and lungs. Subsequent studies continued to find benefits in the practice.

It’s possible that your friend’s interest in IMST arises from a spate of news reports about preliminary findings by researchers from the University of Colorado, which were presented last month at the annual Experimental Biology conference.

The seed for the experiments was planted several years ago, when researchers from the University of Arizona looked into IMST as a way to help individuals living with obstructive sleep apnea. This is a potentially serious disorder in which muscles in the throat relax enough during sleep to completely block airways. In addition to confirming that by increasing resistance, the length of each IMST session could be shortened, the Arizona researchers saw a surprising side effect. After six weeks of therapy, systolic blood pressure in the study participants dropped significantly. Systolic blood pressure -- that’s the top number in a blood pressure reading -- is the pressure in the blood vessels during a heartbeat. (The bottom number is the pressure in the blood vessels between heartbeats.) High blood pressure is one of the major risk factors for cardiovascular disease, which is the leading cause of death in the United States.

The results of the Arizona research spurred scientists at the University of Colorado to build upon the findings. In their own series of experiments, which are ongoing, the Colorado researchers saw the same significant drop in blood pressure in participants who performed IMST. They also recorded improvements to large-artery function. The IMST group also saw improvement in cognitive function and in endurance and heart-lung efficiency while exercising on a treadmill. Neither of those changes were seen in a control group, which used a breathing device that delivered only low resistance.

These results are impressive, but, as the researchers themselves point out, they are preliminary. The researchers stress, and we agree, that anyone considering IMST should first check with their doctor.

(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.)