Dear Doctor: I have heard several stories on the news recently about carbon monoxide-related deaths, and they have me concerned. Where does carbon monoxide come from, and how do I protect my family?

Dear Reader: Carbon monoxide, also referred to as CO, is a colorless and odorless gas that is impossible to detect without specialized equipment. Because of that, it has been called the "invisible killer." About 400 people die each year from CO poisoning, and another 20,000 seek medical treatment.

In the home, carbon monoxide can be produced by fuel-powered devices like stoves, furnaces, water heaters, dryers, boilers and lanterns. It is emitted by wood-burning fireplaces, charcoal grills and generators. Virtually any substance that contains carbon and can burn will produce carbon monoxide as a byproduct.

The reason carbon monoxide is so toxic is that, when we breathe it in, it takes the place of oxygen in our red blood cells. In fact, the chemical structure of CO is such that it binds far more readily to the hemoglobin in our blood than does oxygen.

When you're breathing in an enclosed space where CO is present, your body will become starved for oxygen in a very short time. Cells and tissues that are denied oxygen quickly begin to die. Brain cells, for example, begin to die after just three minutes without oxygen. Beyond that, permanent brain damage begins.

Now, some good news. The presence of carbon monoxide in the home is easily detected by special alarms. Just like a smoke alarm, the CO alarm contains specialized sensors that will activate when the gas approaches unsafe levels. These alarms, which can plug into electric outlets and also have backup batteries, are sensitive, accurate and affordable. In many states, they are required by law.

It is recommended that a CO alarm with a backup battery be installed on every level of the family residence, including the basement, attic and garage. There should also be a CO alarm outside of each sleeping area.

There are several other steps that you can take to keep your family safe.

-- Perform a monthly test of each CO alarm to be sure it is working.

-- Keep a supply of extra batteries on hand, so they can be replaced right away.

-- When you use your fireplace, be sure the damper is wide open. Leave it open until the ashes have completely cooled.

-- Never use your gas stove or oven to heat a room in your home.

-- Never use a portable generator in the house or in any enclosed space. Generators should be kept at least 20 feet from the home when in use.

-- Don't use a gas or charcoal grill inside the home. Be sure to operate grills far away from any open windows.

-- Know the symptoms of carbon monoxide poisoning: weakness, dizziness, sleepiness, headache, weak pulse, nausea, vomiting and confusion.

If you suspect that you or a family member has CO poisoning, immediately go outside to the fresh air, and then call 911.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I've been seeing advertisements for glutathione, saying the supplement enhances the body's cells. The ads also say the claims haven't been evaluated by the Food and Drug Administration. What can you tell me about it?

Dear Reader: Glutathione is an antioxidant produced in the body through enzymatic reactions, using the amino acids cysteine, L-glutamic acid and glycine. It helps repair cells damaged by pollution, stress and other harmful influences, and it is undeniably important.

Mice unable to form glutathione will die before birth. Mice that have been genetically altered to not produce glutathione in the liver will die after one month. People with mutations in the enzymes that form glutathione are more susceptible to oxidative stress. The deficiency in the production of glutathione leads to the breakdown of red blood cells, enlargement of the spleen, gall stones, and after many years can lead to mental deterioration. Also, these patients are more prone to severe anemia when exposed to certain chemicals or drugs.

Less is known about glutathione's use as a general supplement, although it has been evaluated by the FDA for AIDS-related weight loss. People with AIDS have reduced production of glutathione in the intestine, and supplementation with glutathione could help in the ability to digest food.

Glutathione has also been studied in cystic fibrosis patients. Decreased glutathione in their intestines can lead to inflammation of the intestine, pain, decreased absorption of food, weight loss and growth failure. A 2015 study published in the Journal of Pediatric Gastroenterology and Nutrition found that supplementation with glutathione three times per day with meals has been shown to decrease intestinal inflammation and improve growth in children with cystic fibrosis.

Other research assessed glutathione's effect on people with vascular disease of the arteries that go to the legs. Decreased blood flow can lead to calf pain when walking, but the study found that glutathione given intravenously twice a day helped ease patient symptoms.

Because you're presumably healthy, you're unlikely to have any deficiency in the production of glutathione. If you're interested in improving your body's ability to recover from exercise by enhancing your muscles' ability to heal, that's a different question. People who exercise vigorously create oxidative free radicals, which can lead to muscle fatigue and decrease muscle performance -- suggesting that an antioxidant may be helpful.

However, people who exercise regularly naturally produce more antioxidants in the muscles to prevent damage, possibly in response to the regular formation of oxidative free radicals. Regardless, the body takes care of itself without the need of a supplement.

As of yet, there is no good study of the use of glutathione in healthy people. Some nutritionists recommend increasing the intake of the amino acids cysteine and glutamate, which make glutathione, but this hasn't been studied either.

In short, the supplement has shown benefit among cystic fibrosis and AIDS patients who have decreased glutathione in the intestine, and it may show benefit in inflammatory conditions of the intestine, such as ulcerative colitis and Crohn's disease, but this needs to be studied as well.

At this point, I would not recommend taking glutathione. If you're healthy, your body should produce an adequate amount of this important antioxidant.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I understand that Alzheimer's disease causes memory loss and leads to dementia. But when someone has Alzheimer's, what is the actual cause of death?

Dear Reader: Alzheimer's disease is a progressive disease of the brain in which dementia is the most noticeable of numerous symptoms. Changes within the tissues of the brain slowly destroy vital connections between different regions of the brain, and between the brain and the body. The result is that Alzheimer's disease is the fifth-leading cause of death among adults over 65, and is the sixth-leading cause of death for all adults nationwide.

The disease was first identified in 1906 by Dr. Alois Alzheimer, who connected a patient's dementia to certain physical abnormalities he found when he examined her brain after her death. But the human brain is so intricate and Alzheimer's itself is so complex that more than a century later, scientists are still working to discover both the cause of, and a cure for, the disease.

Although each case of Alzheimer's is different, researchers have identified three general stages of the disease. In the first stage, symptoms of cognitive impairment, such as memory loss or confusion, have either not yet appeared or are quite mild. However, significant changes are taking place within the brain, including nerve death, tissue loss and the buildup of abnormal clumps and tangles of protein.

These changes lead to the second stage of the disease, during which symptoms become more pronounced. Patients begin to experience significant memory loss, confusion, impaired reasoning, poor spatial skills and a loss of language. By the final stage of Alzheimer's, the brain has shrunk dramatically. Patients can no longer communicate, are unable to recognize faces, even of family members and loved ones, and are unable to care for themselves.

Patients with advanced-stage Alzheimer's need 24-hour supervision and help with personal hygiene, dressing and eating. Changes in brain function make it increasingly difficult for them to move about, sit up and even swallow. This leads to complications such as bedsores, skin infections, blood clots and sepsis. Injuries from falls are common. Difficulty in swallowing makes eating and drinking an ongoing challenge, and can lead to weight loss, malnutrition and dehydration.

The most common cause of death among Alzheimer's patients is aspiration pneumonia. This happens when, due to difficulty in swallowing caused by the disease, an individual inadvertently inhales food particles, liquid or even gastric fluids. Because our mouths and throats contain numerous bacteria, these are carried deep into the lungs. There they multiply and grow, which leads to pneumonia. Due to the impaired immune systems of Alzheimer's patients, pneumonia is often fatal.

It's important to remember that Alzheimer's patients are often elderly and thus may have a range of medical conditions associated with advancing age. These include stroke, cancer, heart disease, diabetes, hypertension and stroke, any of which can cause death, whether or not Alzheimer's is present.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)